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VEGETATIVE PROPAGATION OF BLUE SPRUCE
(Picea pungens Engelm.) BY STEM CUTTINGS
BY
Anne M. Wagner
A Thesis submitted to the Graduate School
in partial fulfillment of the requirements
for the Degree
. M aster ofScience
Major Subject: Horticulture
New Mexico' State University
Las Cruces, New Mexico
August 19'88.
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Propagation of Blue Spruce (Picea pungens EngcIm.) by Stem
,,:,tt.nac:" a thesis prepared by Anne M. Wagner in partial
fulfillment of the
,.....'rn""'t5 for the degree, Master of Science, has been
approved and accepted by
H. Matchett of the Graduate School
1988
Dr. Jamcs T. Fisher, Chairman
Dr. Dennis Clason
Dr. John G. Mexal
Dr. Mary A. O'Conncll
n
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ACKNOWLEDGMENTS
I would like to take this opportunity to thank Dr. Jim Fisher
who gave me the
opportunity and support to do this research. Thanks to the
members of my
committee, Drs. John Mexal, Mary O'Connell and Dennis Clason,
for their advice
"and encouragement. Many thanks to Dr. Leigh Murray who spent
countless hours
aiding in the design and analysis of this study. In addition,
I'd like to acknowledge
the help and input of Greg Fancher without whom this project
would have been
more difficult, if not impossible. I'd also like to thank
everyone at the Mora
Ke~)ealrcn Center for their help. And to Paul Schaeffer, fellow
graduate student, my
....,QJ"'...... for helping me out and giving me moral support
along the way ..
Many thanks to my family and friends for their encouragement and
faith in me,
my parents for their emotional and fmancial support. Finally, I
would
to thank John Harrington, for his advice, support, his expertise
in graphics, but
for keeping me sane these last few months. ,
ill
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VITA
March 5, 1959 - Born at Concordia, Kansas
1981 - B.S., Fort Hays State University,Hays, Kansas
1981 - 1983 - Forestry Extensionist, U. S!Peace Corps,
Ecuador
1986 -1988 - Teaching Assistant, Department ofAgronomy and
Horticulture,
New Mexico State University
PROFESSIONAL AND HONORARY SOCIETIES
tional Society QfTropical Foresters
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ABSTRACT
VEGETATIVE PROPAGATION OF BLUE SPRUCE
(Picea pllllgens Engelm.) BY STEM CUTTINGS
BY
ANNE M. WAGNER
Master of Science in Horticulture
New Mexico State University
Las Cruces, New Mexico, 1988
Dr. James T. Fisher, Chairman
Techniques for vegetative propagation of blue spruce (Picea
pungens EngelrU.)
stem cuttings were investigated. Time of collection 'of the
cuttings, application
exogenous rooting hormones and source differences were examined.
In apdition, .
position, cutting length, caliper and fresh weight were'looked
at in relation
rooting response.
v
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Using 100year-old field-grown blue spruce at the Mora Research
Center,
terminal cuttings were taken from 120 trees every 4 weeks from
December 1986 to
May 1987; Three New Mexico sources were used. From each source,
10 trees were
assigned to each of 4 hormone treatment levels. The hormone used
was
3-indole-butyric acid (IBA) and was applied as a 5 sec. quick
dip to the basal end
of the cutting. Hormone levels were control (no IBA), 2500 ppm
IBA, 5000 ppm
IBA and 10,000 ppm IBA. Cuttings were placed under a wet tent
with bottom heat
of 20C for 20 weeks. Rooting, shoot activity and root
characteristics were
quantified.
Overall, rooting was low, with 107 of 1440 rooting. In addition
to higher
rooting rates for cuttings taken in December and February,
number of roots
initiated, root length and root weight were highest for cuttings
made in December.
Hormone level was significant only in rooting response. The
levels most favorable
for rooting were the control and 2500 ppm IBA. Source
differences were also seen
in rooting response. Cuttings from the Cloudcroft source rooted
at higher levels
than did the other 2 sources. The cuttings from the lower part
of the tree were
more likely to root, have more primaries initiated and more
likely to break bud.
Shorter cuttings were more likely to initiate. roots than longer
cuttings.
From this study, it appears as if timing of collection is the
variable of greatest
importance in rooting of blue spruce stem cuttings. The most
favorable time of
collection for root initiation, root biomass, number of roots
initiated and root
length was December. Hormone treatment did not appear to enhance
rooting or
alter rooting characteristics, except in the later collections.
Cutting position and
vi
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length appear to play some role in root initiation. The possible
role of shoot
activity in root initiation is also discussed.
vii
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TABLE OF CONTENTS
LIST OF TABLES .......................................... x
LIST OF FIGURES ........................................ xi
INTRODUCTION .......................................... 1
LITERATURE REVIEW ..................................... 3
Root initiation .............................................
4
Clonal variation ........................................... ~
6
Juvenility .................................................
6
Date of collection ...........................................
9
Rooting environment ................................ /. . . . ..
11
MATERIALS AND METHODS .............................. 17
, RESULTS ............................................... 24
Rooting response ..........................................
24
Root analysis ............................................
31
Root fresh weight .......................... :.............
31
Primary root number ................................... ~.
36
Root length ...................... '. . . . . . . . . . . . .. .
. . . . . . . .. 39
Shoot activity .............................................
42
Shoot analysis ................................... ~ . . . . . .
. . 44
Cutting length ...........................................
47
Final cutting weight ....................................... 5.0
>
DISCUSSION ............................................ 55
Collection date .....' .............. ;........................
56
vw
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Hormone level ............................................
57
Cutting characteristics ......................................
57
Root production ...........................................
58
Shoot activity .............................................
60
Final shoot characteristics ....................................
61
Conclusions ..............................................
61
LITERATURE CITED ..................................... 63
APPENDIXES
A. Weather data for the Mora Research Center ...................
67
B. Propagation bench environmental data .......................
73
ix
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LIST OF TABLES
Table I. Significant interactions
..............................................................................
25
Table 2 .. Observed frequencies of rooting by height ratio
...................................... 30
Table 3. Mean root fresh weight by collection date
............................................... 34
. Table 4 .. Mean total number of primary roots by collection
date ......................... 38
Table 5. Mean sum of root length by collection date
............................................ 41
Table 6. Mean final cutting length by collection date
............................................ 48
Mean fmal shoot fresh weight by collection date
.................................... 52
x
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LIST OF FIGURES
Figure 1. Percent of cuttings rooted by collection date
........................................ 26
Figure 2. Percent of cuttings rooted by hormone level
.......................................... 27
Figure 3. Percent of cuttings rooted by source
...................................................... 29
Figure 4. Logistic regression of initial cutting length and
the
pro ba bility 0 f ro 0 ting .......... .............
............................................................ ....
32
Figure 5. Means of root fresh weight of rooted cuttings by
hormone
Figure 6 (a - c). Mean root fresh weight of rooted cuttings
by
Figure 7 (a - c). Mean total number ofpriroary roots of
rooted
Figure 8 (a - c). Mean sums of root length of rooted cuttings
by
level and collection date
;..................................................................................
35
collection date .............:
.....................................................................................
37
cuttings by collection date
................................................................................
40
collection date ................................ :
..................................................................
43
9. Probability of budbteak of cuttings after harvest
by source
...........................................................................................................
45
10. Probability of bud break of cuttings after harvest
by collection date and hormone level ........ ;
..................................................... 46
11. Mean final length of cuttings by source .
and collection date .............. ;
..............................................................................
49
12. Mean final fresh weight of cuttings by source
and collection date
...............................................................f
............................ 53
13. Mean final fresh weight of cuttings by hormone
level and collection date
....................................................................................
54
Xl
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INTRODUCTION
Blue spruce (Picea pungens Engelm.) IS utilized throughout the
United
States primarily as an ornamental but also as a Christmas tree.
The blue
spruce's naturally attractive form and broad ecological
adaptiveness has made
it a valuable ornamental. The natural range of blue spruce
extends through
the southern Rocky Mountains, from southern Idaho to New
Mexico.
Hanover (1975) identified New Mexico sources as among the best
for color
development and rapid growth. Blue spruce matures slowly,
generally not
setting seed until age 30. Due to distinct geographic ecotypes
exhibiting
variation in form color and growth rates, the ability to
vegetatively propagate
superior trees would be advantageous in an improvement
program.
Variable success has been reported in attempts to vegetatively
propagate
blue spruce. Thimann and DeLisle (1939, 1942) achicved 80%
rooting success
with cuttings taken in April from trees 10 to 20 years old, with
less success in r
November, and no rooting in other months. Hanover (1975)
successfully.
rooted 85~/O of cuttings from trees 30 to 60 cm tall. Rooting
success of
cuttings from one-year seedlings varied from a low of 10% to a
high of 80%
(Struve, 1982). Cultivars of blue spruce appear to root more
rcliably when
-
cuttings are taken in January than in the summer months (Iseli
and Howse,
1981). The consensus among growers appears to be that cuttings
should be
taken in late winter or early spring and treated with rooting
honnones to
achieve maximum rooting response.
The objective of this study was to develop methods for
vegetatively
propagating blue spruce by stem cuttings as well as identifying
important
factors affecting rooting response. The factors of interest
selected were timing
of collection and rooting honncine application. In addition,
several covariates
were examined, which included cutting position on the tree,
cutting length and
stem caliper of the cuttings.
,
2
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LITERATURE REVIEW
. Rooting responses seem to hinge on competence of a cutting to
initiate
roots. . Rooting in conifers requires the synthesis of root
primordia unlike
some species which have preformed root initials. Factors which
influence the
comp.etence of a cutting to initiate roots include: genotypic
differences,
physiological differences and propagation techniques. Three
distinct phases of
root meristem development have been described cell division,
directional
growth and cell differentiation.
After the stem cutting is made, callus usually forms. Callus
is
undifferentiated tissue which forms as part of a wound response.
Callus
. develops mainly from cell divisions in the new meristematic
area formed in the
cortex, after the stem cutting is severed, although phloem and
cambial cells
can also develop callus. After the callus forms, a few of the
meristematic cells
will form root primordia. Adventitious root meristems (i.e.,
root primordia)
are preceded by lateral extension of callus xylem or by
formation and
extension of tracheid nests (Cameron and Thomson, 1969) .. From
the root
primordia, roots will initiate and develop.
3
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Root initiation
The process of root initiation has been described for cuttings
of juvenile
Pinus radiata and P. banksiana. The first observable event in
root initiation of
P. radiata cuttings from seedlings is the formation of a
meristematic locus
(Smith and Thorpe, 1975a). Asymmetric division in surrounding
meristematic
loci leads to the foonation of meristemoids which differentiate
into root
primordia. Less clear are the events leading to root initiation
in P. banksiana.
The callus originates from the cortex remaining after stem
dieback due to the
basal wound (M ontain et al., 1983a, b). The callus tissue
differentiates into a
complex mass of tissue containing vascular tissue, tracheid
nests and resin
canals. The root primordia are fooned from the callus apparently
associated
with the resin canals.
Endogenous factors are known to playa role in root primordia
formation
as well as root initiation and development. Smith and Thorpe
(1975b) found
there are two stages when the presence of auxin is essential in
root initiation
. and development. The first stage is marked by the initial
events leading to
meristematic locus formation and the second by events
immediately preceding
meristemoid development. However, indications are that more than
auxins
are needed for root initiation. Hess (1965) proposed that there
were 4 rooting
co-factors which act with auxin to induce rooting. Only 2 of the
rooting
cofactors were identilled by Hess. The active component of
cofactor 3 was
identified as isochlorgenic acid and cofactor 4 consisted of
oxygenated
tcrpenoids. Girouard (1969) found rooting co-factors present in
Hedera helix.
4
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Girouard further defmed the active components of the rooting
cofactors.
Cofactor 1 could not be identified. cofactor 2 contained
chlorogenic acid"
cofactor 3 was found to consist of chlorogenic acid and an
unknown promoter
as well as isochlorogenic acid, and cofactor 4 was again
identified as
oxygenated terpenoids. Comparing products of easy-to-root and
hard-to-root
pear cultivars, Fadl and Hartmann (1967) identified a rooting
co-factor which
they suggested could be a condensation product between exogenous
auxin and
an endogenous phenolic compound. Furthermore, extracts from
the
difficult-to-root cultivar lacked this compound.
Haissig,(1974) argued in a review of the effect of auxin on
rooting, that
while auxin is a key to rooting, another compound needs to be
present, '
possibly an auxin-phenol complex. Evidence that auxin alone
cannot induce,
rooting is suggested by studies with juvenile Pinus banksiana.
When the
tenninal buds were, removed from cuttings, rooting was inhibited
and this,
condition could not be overcome by exogenous applications of
auxin (Haissig.
1982). Increased rooting responses resulting from the use of
N-phenyl
indoyl-3-butyramide or phenyl indole-3-butyrate but not from
simple auxin
seem to support this theory (Haissig, 1983; 1979). Apparently
the synthetic
supplemented auxins substitute for the naturally occurring'
auxins and
cofactors to promote rooting.
5
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Clonal variation
Clonal variation is an important factor in rooting potential,
yet its
underlying cause is not understood. Among trees' from the same
seed source, .
some will yield more cuttings tHat promptly initiate roots while
cuttings from
others fail. Because differences in age and physiological state
are apparently
nonexistent, rootability must be related to genotypic causes.
Williams (1987)
found between tree variation in mature western white pine which
could not be
altered by honnone treatment. Donor tree success ranged from a
low of 10%
to a maximum of 87%. Several species of spruce have been found
to vary by
tree in response to honnone treatment and bottom heating of
rooting medium
(Rauter, 1971). It appears as if some internal threshold has to
be reached, or
a level of competence which is as yet undefmed (Haissig, 1982).
This becomes
a concern m the selection of individual trees (i.e., specific
genotypes) for
propagation. Superior individuals or provenances may not root
readily and
are therefore eliminated from propagation programs. Another
related concern
is the deselection of genotypes resulting from rooting failure
among clones
. (Struve, 1982).
Juvenility
A major problem encountered in vegetative propagation of woody
plants is ~
the loss of the ability of a cutting to initiate roots. as the
stock plant ages.
Cuttings from juvenile. trees generally are easier to root than
those taken from
mature trees. Adventitious root initiation is considered to be a
juvenile
6
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characteristic related to ontogeny (Hackett. 1985). Clark (1981)
identified four
areas linking maturation state and rooting. The areas of
importan
stem anatomy. which causes physical barriers to root initiation,
rooting
co-factor levels, endogenous rooting inhibitors and the presence
of preformed
root initials.
Problems associated with maturation are more severe in some
clones and
cultivars than others (Kester, 1976). However, the end of the
juvenile phase
of a woody plant is not easily determined. Kester (1976) stated
the control of
maturation is mainly a function of the development of the
vegetative
meristem. The length of the juvenile phase is determined mainly
by the
number of cell divisions that have occurred in a vegetative
meristem rather
than its chronological age. Often maturity is defined as the
capacity for
sexual reproduction. However, while the ability to set seed is
rather easily
determined, it appears that is not ~ecessarily a good indicator
of juvenility in
terms of rooting capacity. There is evidence that loss of
rooting potential
often is not marked by the arrival of the capacity for sexual
reproduction and
therefore can be related to other factors. Clark (1981) contends
the loss of
rooting ability and the capacity to form flowers are distinctly
different
physiological processes.
Roberts and Moeller (1978) examined rooting pot~ntial of
Douglas-fir as
related to achieving reproductive maturity and found the
decrease in rooting
not dependent on cone production or flowering. The reduced
rooting
potential was instead correlated to other factors related to
physiological
7
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maturity. Rooting potential of 16-year, cone-producing trees was
found to
change little when compared with 12-year trees. By age 16 most
of the trees
were producing cones. However, rooting potential did change
within the trees,
with a higher rooting potential in the lower one-third of the
crown. Although
this change was somewhat tree-dependent, Roberts and Moeller
suggested the
loss of rooting potential may be localized within a tree.
Another phenomenon associated with agmg IS that tissues found
at
different locations on the same tree differ in juvenility.
Paradoxically, tissues
at the top of the tree are vegetatively 'mature' but are the
youngest tissues in
chronological age. Conversely, the oldest tissues found near the
base of the
tree tend to be more juvenile (Kester, 1976). In 16-year
Douglas-fIr, the
rooting potential of the upper two-thirds of the tree was found
to be
significantly less than the lower one-third of the crown
(Roberts and Moeller,
1978). This would appear to support the argument that the lower
portion of
the crown is more juvenile, even though in some trees cone
production can be
most abundant in the lowest whorl of branches (Roberts and
Moeller, 1978).
Schwabe (1976) implicated proximity to roots as a factor in
juvenility of
shoots. Specillcally, juvenility is related to a
gibberellin-like factor associated
with the roots. Gibberellin inhibits flowering and the
accumulation of f
carbohydrates in the shoots.
Rootability has been related to crown position effects occurring
in juvenile
seedlings as well as sexually mature trees. Phillion and
Mitchell (1984) found
that cuttings from the lower two-thirds of IS-month conifer
seedlings rooted
8
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somewhat better for all the clones they examined. The effect of
crown
position on rootability was most pronounced among clones
yielding rootable.
cuttings exclusively from the lower one-third of the crown. It
was speculated
that because this clone was the tallest, it might be escaping
juvenility and the . drop in rooting was due to this difference in
height, and perhaps greater
maturity.
Branch order also plays a significant role in rooting potential.
Secondary
lateral branches tend to root better than do primaries (Farrar
and Grace, .
1942). However, secondaries exhibit more plagioiropic growth,
which is ~
common problem encountered in propagation programs. However,
Miller
(1982) found in Fraser frr cuttings that differences in rooting
responses
attributed to secondary and primary shoots were eliminated when
exogenous
auxins were applied to cuttings harvested from them.
Date of coUection
Seasonal variation in rooting response is a major factor in
vegetative
propagation. Season obviously plays ~ role in physiological
conditioning of
the stock plant which in tum affects the rooting response of the
cutting.
Lanphear and Meahl (1963) found root-forming capacity of
cuttings from two
evergreen species was seasonal, in that it peaked in late fall
and winter. This
relationship could not be altered by the application of an
exogenous
root-promoting auxin.
9
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Roberts and Moeller (1978) concluded from a study on Doug1as~frr
that
seasonal periodicity of shoot development has a controlling
influence on
rooting potential. The rooting potential of Douglas-frr cuttings
was found to
be correlated with stage of shoot dormancy. State of rest
(dormancy) was
determined by the speed of budbreak. Dormancy increases from the
onset of
rest until the bud chilling requirement is met, then begins to
decrease until
budbreak occurs. Dormancy (state of rest) is often measured by
the number
of days to budbreak (Kobayashi et aI., 1982). Rooting capacity
was lowest
when shoot dormancy was greatest. When the chilling requirement
of shoot
buds was met, in January and February, rooting potential was
maximum. At
midrest, November, auxin promoted rooting in excised cuttings.
Norway
spruce was found to root best when cuttings were taken in April
and May
(Girouard, 1975). Rooting response was maximized when cuttings
were taken
just before or during budbreak. The second best rooting was
October to
November, when bud dormancy was not yet complete.
Similar results have been seen in studies on Fraser frr cuttings
(Hinesley
.. and Blazich, 1984; Struve and Blazich'f 1984). Hardwood
cuttings root well in
late January and February, after the chilling requirement of
buds had been
met. When cuttings are . dormant, neither budbreak nor. rooting
can be
initiated. Chilling studies indicate that more chilling is
needed for budbreak
than for root initiation. Rooting capacity can drop after
February as the
date of budbreak becomes imminent. Because collection date
determines total
chilling units received, this factor has been shown to be the
source of greatest
year-to-year variability in the rooting of Fraser fir stem
cuttings.
10
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Even an easy-to-root species such as Salix appears to have
distinct phases
during which root initiation will occur. Levels of endogenous
indoleacetic acid
(lAA) and rooting were correlated, but not enough to conclude
that rooting
response is governed by hormonal levels (Vieitez and Pena,
1969). Tognoni et
al. (1977) identified a substance from Picea glauca cuttings
which varied with
season and could be positively correlated to rooting responses.
The substance
was tentatively identified as abscissic acid, a known growth
inhibitor. Nanda
et al. (1968) concluded that the effectiveness of auxin in
promoting rooting
differed among species as well as season. More recently, Wise et
al. (1985)
showed that IBA effects varied with date of collection. Lanphear
and Meahl
(1963), on the other hand, concluded that positive effects
derived from high
levels of IBA and periods of high root formation were
synergistic in
stimulating root initiation. In addition, no correlation was
found between
rooting cofactors found and root-forming capacity.
Rooting environment
Success in rooting of cuttings u,:volves more than selection of
quality
cutting material. The rooting environment is of importance. The
propagation
environment should optimize any biological potential for
rooting.
Environmental factors are critical, although some appear to be
of greater
importance than others. Factors of importance include soil
temperature,
water, both soil and relative humidity, light, air temperature,
and media
composition.
11
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Bottom heat, the heating of the propagation bed or rooting
medium to
temperatures between 18C and 30C, is generally accepted as
beneficial to
the rooting of cuttings. Ticknor (1969) noted that several
conifer species show
increased rooting in response to bottom heat, but in other
species higher soil
temperatures were detrimental. In outdoor tent propagation
systems, bottom
heat of 22C proved detrimental to some plants (Pellet et aI.,
1983). Bottom
heat inhibits the rooting of westem hemlock (Shinn, 1983) yet
torulosa juniper
can only be propagated using bottom heat of 21 to 240C
(Wetherington,
1983). Heating of the soil medium (18 - 21C) generally improves
the rooting
response of Douglas-fir cuttings (BheIla and Roberts, 1974; Brix
and Barker,
1973). However, Rauter (1971) found that bottom heat was
detrimental to
. several species of spruce, most notably black spruce.
Unfortunately, the
temperature was not reported. The level and effectiveness of
bottom heat
appears to be species dependent.
In 1969 van Elk reported that bottom heat in conifers generally
resulted in
.increased rooting responses. In addition to improved rooting,
Canadian
. hemlock developed a larger root sy"'stem with bottom heat.
However, it was
noted that other treatments, such as fungicide applications,
could compensate
for absence of bottom heat.
In examining the benefits of bottom heat Dykeman (1976)
separated
rooting into two processes: root initiation and root elongation.
Root
initiation was defined as primarily cell division, and root
elongation as cell
.' elongation and differentiation. This approach recognized the
possibility that
12
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each process can have a different optimum temperature and
allowed root
initiation and elongation responses to be examined separately.
While not
attempting to defme optimum temperatures for each process,
Dykeman
reported that temperatures of 30 to 35C resulted in quicker
emergence of
root initials and more roots initiated in Chrysanthemum and
Forsythia.
However, temperatures of 35C inhibited growth and development of
the
roots, even causing death of the root within days. Temperatures
below 25C
were shown to enhance root growth. In practical terms it would
be difficult to
determine when to change media temperatures in propagation
operations.
However, the effects of media temperatures on root initiation
and
development must be known to allow for better choices in
selecting media
temperature.
Brix andBarker (1973) examined the effects of bottom heat in
relation to
air temperature. Western hemlock cuttings collected in the fall
responded to
no heating of air or soil medium (bjlt kept frost-free).
Douglas-fir cuttings
taken in November rooted only in a cold air-warm soil (200C)
environment ..
Cuttings were taken September through March. Cold air-warm soil
was most
beneficial to the rooting of Douglas-fir through January.
February and
March cuttings did not respond to cold air-warm soil treatments.
Cuttings
from Douglas-fir never responded well to warm air-warm soil
treatments,
although cuttings from seedlings did root in a warm air-wann
soil
environment.
13
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In another study using Douglas-ftr, Bhella and Roberts (1974)
reported
cuttings rooted better with media temperatures of 18 and 26C
than with
Woe. The observed increase in bud respiration at 18 and 26C
was
correlated to an increase in rooting. At lower temperatures the
decrease in
rooting was possibly linked to slowed metabolism, as indicated
by lower bud
respiration. Higher soil temperatures also caused an increase in
basal callus
formation, an important step in root initiation. In a later
study, optimum
rooting temperatures for Douglas-ftr were narrowed to between 18
and 21C.
Also interactions between daylength and media temperatures in
the rooting
environment influenced rooting (Roberts and Moeller, 1978).
Other factors can interact with bottom heat in influencing
rooting,
including auxin activity, air temperature and transpirational
losses. Scott
(1972) indicated increased auxin activity at higher
temperatures. Because of
the key role auxin has in root initiation, the possible
enhancement of auxin
. activity with raised temperatures would be beneficial. On the
other hand,
increasing media temperatures will also signillcantly increase
air temperature
at the cutting level (Gislerod, 1983). The increased air
temperature will ... increase the transpiration loss in the shoot,
b~t adverse responses can be
minimized or eliminated when fog and/or mist systems are used in
conjunction
with higher temperatures.
Tissue water status can strongly influence rooting success. A
favorable
environment in terms of relative humidity and ample water is
critical for
survival of the cutting. By using mist instead of double glass,
Hess (1965)
14
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found increased ,rooting as well as number of roots initiated
and root length.
Relative humidity in the two propagation systems were the same
but leaf
temperature was significantly lower in cuttings under mist. Mist
was effective
in cooling the cuttings through evaporation. In addition, less
light was
allowed to reach the glass-grown cuttings because shading was
used to
decrease temperatures through reduced incoming radiation to the
cuttings.
The combination of higher temperatures, which led to increased
transpiration,
and reduced photosynthesis under lower light resulted in lower
rooting
success. More recently, Howard (1980) found humidity in the
rooting
environment greatly influenced root formation.
High leaf water potential has been correlated to rooting success
(Loach,
1977). Water uptake from the medium by cuttings is restricted by
a contact
resistance between cutting and medium. In addition~ there is
astern resistance
to water uptake"'which develops within several days of stem
insertion into the
medium. Therefore, factors influencing tissue water balance in
the cutting
indirectly influences rooting success. (Grange and Loach,
1983a).
One of the major factors influencing water loss is daily solar
radiation. As.
radiation increases, transpiration also increases (Hess, 1965;
Loach, 1977).
Grange and Loach (l983b) found leaf tissue water content of
cuttings
inversely proportional to daily radiation. Some cuttings can
offset the
resistance to water uptake. and .water loss by water absorbtion
directly through
the leaf. Whitcomb etal. (1982) developed a system that
reduces
transpirational losses. as well the a,inount of mist that must
be applied. The
15
-
wet tent propagation system provides high humidity with limited
misting.
With a wet tent, water evaporates from the fabric as
temperatures rise and the
humidity increases inside the tent.
In conclusion, propagating conifers from stem cuttings is
difficult. Many
factors can be involved which can directly or indirectly
determine success or
failure of a cutting to root. Stock plant conditioning is of
major importance
as is defmed by physiological state of maturity and dormancy.
Rooting
hormones may be necessary to optimize rooting capacity.
Post-severance
environment is also of interest in tha~ appropriate growing
conditions are
necessary for root initiation and development.
16
-
MATERIALS AND METHODS
Stock plants were selected from a blue spruce provenance study
planted in
1978. at the Mora Research Center. From 19 sources. 3 New Mexico
sources
were selected for this study. Sources were selected based on
mean height and
color. The 3 sources selected were from Cloudcroft, Junction La
Junta near
Mora. and Willow Creek on th~ Gila National Forest. The
objectives of the
study encompassed several aspects, most of which involved
techniques of
propagating blue spruce. The primary objective was to determine
if there were
any differences in timing of collection on rooting success of
cuttings.
Secondary objectives included quantifYing the effects of rooting
hormone and
the effect on root initiation and development. and any
differences in rooting
potential among different seed sources. Tertiary factors of
interest were the
effect of cutting position. basal stem caliper and cutting fresh
weight on
rooting. The selection of 3 sources was made in an attempt to
identify source
variation in rooting response. as well as maximize potential
rooting success.
From each source. 40 trees were selected. Within each source,
the trees
were selected based on form, color and height characteristics. A
total of 120
trees were used in this study. All trees were un sheared and the
plot was
thinned to a 1.7 m by 2 m spacing the previous year. No
fertilizer had been
17
-
applied during the previous growing season, but had been
unifonnly applied in
1985,
Due to the number of cuttingl; available from each tree, 6
collection dates
were selected in an attempt to identifY optimum time of
collection. Previous
work conducted elsewhere indicated blue spruce roots best in
late winter to
early spring (Hanover 1975) .. Collection dates were selected to
permit harvest
at 4-week intervals beginning in December 1986. Cuttings were
harvested on
the following dates: 20~2l December 1986, 17 January 1987, 14
February
1987, 13 March 1987, 9 April. 1987 and 8 May 1987 (see Appendix
A for
weather data).
Indolebutyric acid (IBA), a synthetic auxin, was used to
determine if
rooting potential could be altered by treatment with exogenous
auxins. Three
hormone levels were selected along with a control (no hormone).
The 4 . .
treatments were control, 2500. ppm IBA, 5000 ppm IBA and 10,000
ppm IBA ..
Each tree was randomly assigned to one of the 4 hormone levels
initially.
The study required 12. cuttings from each tree.Cuttings
harvested from each
tree at the assigned intervals received the same hormone
treatment throughout
the course of the study to eliminate tree-to-tree variation. Two
cuttings were
taken from each tre.e at each collection time. Cuttings from a
total of 10 trees
per source received the same (teatmcnt. For each collection, 240
cuttings were
stuck, with 60 cuttings for each hormone level. A total of 1440
cuttings were
used in the study.
18
-
At each collection, the cuttings were harvested in the same
manner. Only
primary lateral shoots with terminal buds were harvested and
these included,
only the growth produced the previous growing season. Initially,
tree height
was recorded for each tree before cuttings were taken. As each
cutting was
taken, the vertical distance between the ground and the point of
stem
severence was recorded (cutting height). Cuttings \vere
subsequently placed in
paper bags with labels identifying origin by source and tree.
All cuttings from
a source were taken before any were treated. The maximum l~g
time between
cutting and sticking of the cuttings was approximately 4
hours.
In the laboratory, the basal end of the cuttings were recut at a
45 angle,
and if old wood was present it was removed at the time of
recutting. ' Final
cutting length, basal stem caliper and cutting fresh weight were
,recorded.
Cutting lengths varied from 3.7 cm to an arbitrary maximum of'
12.5 cm.
Needles were not stripped from the base of the cuttings.
Cuttings were then treated with a 5-s~cond quick dip of the
basal 2 cm in
the prescribed treatment. The 3 hormone treatments containing
indolebutyric
acid (IBA) were dissolved in 50% isopropyl alcohol. Control
cuttings were
dipped in a. 50% alcohol solution. After drying for' .10 minutes
the basal
portion of the cuttings were dipped in a 1:1 Captan
fungicide/talc mixture_
The cuttings were then immediately stuck in' 25 cm3 polyethylene
containers
(Ray Leach tubes) to a depth of approximately 2.5 cm.
19
-
The containers were previously filled with a 1: 1
venniculite/perlite mix
(v/v). The filled trays were placed on the propagation bench in
a randomized
(by treatment) design. The trays containing the cuttings were
placed in a
preselected zone on the propagation bench to minimize edge
effects created by
temperature, light and humidity gradients. Border. cuttings were
placed
around the perimeter of the grouped trays to further reduce
border effects.
The unused zones of the propagation bench were filled with blank
tubes with ,
media to prevent heat loss and to maintain uniform bench
temperature.
The bench utilized for vegetative propagation is located in the
center of the
greenhouse with an east-west orientation. The mist bench system
is a
modification of the wet tent system designed by Whitcomb et al.
(1~82).
Fluorescent lights are located 105 em above the floor of the
bench to provide
24-hour photoperiod. A Biotherm heating system, used to provide
bottom
heat, is supported by a redwood frame and covered with expanded
metal to
accommodate growing containers. The Biotherm system was
installed in
accordance with the manufacturer's specifications. Controls were
set at 20C
to provide bottom heat for the cuttings. The sensor which
controlled bottom
heat was placed in the center of the study.
Relative humidity was kept high through the use of two
independent
systems applying moisture to the bench. A 100% polyester fabric
draped over
a pitched metal frame attached to the top of the bench provided
the enclosure
for maintaining relative humidity. The polyester fabric allowed
air to circulate
through while keeping the humidity high. Anautomated
track-mounted boom
20
-
located 1.0 m above the bench was controlled by an automatic
clock timer.
Speeds and frequency were adjusted as needed to maintain
humidity 65% + /~
10%. The boom contained nine fan~type nozzles to provide uniform
mist
particles to the cuttings. In addition, above the tent was a fog
system
controlled by an evaporative leaf moisture meter. The fog system
kept the ..
tent wet and helped maintain the humidity in the propagatiori
bench.
Cuttings were fertilized with Hoaglands solution applied with a
hand
applicator. Cuttings were fertilized 3 times a week to
compensate for the
effects of leaching from the mist applications.
All environmental data were recorded with a Campbell
Scientific
Datalogger CR7. Data recorded included. relative humidity at
cutting level
and 1.2 m above the cuttings. Media temperature was measured
with 2
thermocouples; air temperature at cutting level was also
measured with 2
thermocouples. Natural light levels were measured with two
LI~200S silicon
pyranometers, and soil moisture was measured using gypsum blocks
in 2
locations (see Appendix B). Soil temperatures were maintained
.at 20C + /~
2C, air temperatures were maintained at 20C + I-5C. Soil
moisture levels
were kept at ~0.2 bars +1- 0.1 bars.
Cuttings were removed from the bench after 20 weeks. Treatment
blocks
were removed individually, with all measurements being made
withIn 72 hours
of removal from the bench. If cuttings were removed in: advance
of
evaluation, they were placed in a walk-in refrigerated cooler at
4C. All
cuttings were destructively sampled.
21
-
For each cutting the following attributes and measurements were
recorded:
Cutting condition: ,
0, dead
l,alive
2, callused
3, rooted
Shoot elongation:
0, no activity
1, budbreak or elongation
Shoot measurements:
shoot length
shoot caliper
shoot green weight
Root measurements:
primary root number
primary root length
secondary root number (total)
secondary root length (sum)
tertiary root number (total)
tertiary root length (sum)
total root fresh weight (primary and associated root total)
.
22
-
Primary roots were deflned as originating from the cut end of
the cutting, or ""
callus tissue (if present). After evaluation, cuttings and roots
were oven-dried at
The experimental design was a split-plot design. The whole plot
treatment
design was a 3 ( source) X 4 (hormone) factorial. Collection
date was the split
factor. Cutting height to tree height ratio, [mal cutting
length, basal stem caliper
and cutting fresh weight were used as covariates. Statistical
analyses were done
using analysis of variance techniques (GLM, SAS Institute,
1985). Range tests
were done using the Student-Newman-Keuls test. Discrete data
were analyzed
using categorical model analysis (chi-square tests) and logistic
regression. For
analysis, the total number of primary roots was used for each
rooted cutting. Root
length and root fresh weight were totaled to give a single value
for each cutting.
Height ratio was a variable created by taking the ratio of
cutting height over the
total tree height.
23
-
RESULTS
Overall rooting was low, with 107 cuttings out of 1440 rooted.
Rooting
response was highest for the first collection dates, dropping
off in the spring.
Rooting response varied somewhat with honnone level and source.
Tree-to-tree
variation as well as within-tree variation in rooting response
was observed. Table I
gives a summary of significant interactions over all variables
analyzed.
Rooting response
After restricting cutting condition classification to only two
categories, rooted
and not rooted, a categorical model analysis (SAS Institute,
1985) was used to test
for significant effects. Collection date, honnone level and
source showed significant
effects on rooting response. Collection date was highly
significant with a X2 value
of 6.26 (probability < 0.0001). By collection date, rooting
was highest in
December at 15%, followed by 13% in February. There was a drop
in rooting in
January; and overall rooting declined steadily after February
(Fig. 1). Source and
honnone level were significant at the 10~/Q level (X2 = 4.65,
6.26; probability
=0.0979, 0.0996, respectively). Best treatments were the control
and 2500 ppm
IBA with rooting percentages of 9% and 11%. Rooting success
dropped at the
higher levels of IBA (Fig. 2). Best rooting was found in the
Cloudcroft source with
24
-
Table 1. Significant interactions between variables measured
during rooting of IO-year blue spruce stem cuttings from December
1986 to May 1987.
SUMMARY OF CATEGORICAL ANALYSES
Rooting Shoot Root Root Root Final Final fro wt. no. length
shoot shoot fro
length wt.
Source (:to) '" Collection Date '" * * '*'" Hormone (*)
Source:l: CD '" '" Source * Hormone Hormone * CD '" '" '"
>I:Horm '" Source >I: CD * '" SUMMARY OF LOGISTIC
REGRESSIONS
Cutting length *(+) '" Ht. ratio *(+) * (-)
Caliper * '" Fresh wt. '" '*
'" = significant, P < 5% (*) = significant, P < 10%, . +
,- = sign of estimated slope
25
-
PERCENT
Q IV 0
MONTH
FIGURE 1. PERCENT OF CUTTINGS ROOTED BY COLLECTION DATE.
(PERCENTIS BASED ON TOTAL NUMBER OF CUTTINGS TAKEN FOR EACH
COLLECTION DATE)(N = 240)
-
.,
PEHCENT
oupp
18/\
FIGURE 2. PERCENT dF CUTTI~GS ROOTED BY HORMONE LEVEL.(PERCENT
IS BASED ON TOTAL NUMBER OF CUTTINGS TAKENFOR EACH COLLECTION DATE
(N = 360
27
-
rooting of 11 %. The Junction La Junta source and the Willow
Creek source had
5% and 7% rooting success, respectively (Fig. 3). However, none
of the source by
collection, honnone by source, honnone by collection or honnone
by source by
colled:ion interactions were significant.
In addition, tree-to-tree variation in rooting response of
cuttings was observed.
Individual tree rooting response varied from 0 to 50%. By
source, cuttings from 30
of the 40 trees representing the Cloudcroft source sampled in
the study rooted at
least once. Cuttings from only 15 of the 40 trees from the
Willow Creek source
and 14 of 40 trees from the Junction La Junta source rooted at
least once.
Logistic regression was used to analyze rooting response in
relation to height
ratio, initial cutting length. initial caliper and initial green
weight. The natural
logarithm of the ratio of the probability of not rooting over
the probability of
rooting (called the logit response) was used as a response and
the slope and
intercept.of the line representing the relationship were
calculated. Only height ratio
and initial cutting length had detectable effects on rooting
response. The relation
between rooting and height ratio was seen when the height ratio
data was
transfonned into categorical data (Table 2). Vertical position
or"the cutting on the
tree did influence rooting success. The chi-square test of
independence found that
rooting and cutting height are not independent factors. The
cuttings from the
lower third of the tree showed rooting rates that exceeded the
expected value.
28
http:intercept.of
-
PEf
-
Table 2. Observed frequencies of rooting and no rooting by
height ratio. Height ratio (cutting height I tree height) is
categorized by thirds.
Height ratio
0-0.33 0.34 - 0.66 0.67 -1.0
Observed
No rooting 29 696 608
Rooting 9 62 36
Degrees of freedom = 2 Chi-square = 18.384 Probability =
0.000
30
-
There was a significant relation between initial cutting length
and rooting (Xl =
54.95, probability < 0.0001). \Vith a positive slope estimate
.of 0.337, as cutting
length increased the probability of rooting decreased (Fig. 4).
Probabilities of
rooting were generated using this relationship. For the shortest
cutting, 3.7 cm,the
estimated probability of rooting was 400/0. The probability of
rooting dropped
significantly as cutting length increased to a maximum of 12.5
em to 3%.
Root analysis
For the analysis of root data, 3 variables were used as
indicators of root quality.
Root fresh weight, number of primary roots and root length were
analyzed. Due to
low rooting response for the April and May collections, those
dates were omitted
. from further analyses of root data. Root data were analyzed
using GLM (SAS
Institute, 1985). Due to the small number of rooted cuttings,
normality
assumptions were not met and while significant affects may be
determined, p values
may not be accurate.
Root fresh weight
. Significant differences in root fresh weight were detected
among collection dates.
The mean sums of root fresh weight were analyzed using the
Student-Newman-Keuls test. December cuttings showed a
significantly greater root
mean weight than the other. collection dates which did not
differ significantly.
December cuttings had a mean root fresh weight of 0.124 g, the
mean fresh weight
for cuttings taken in March was 0.055 g, and 0.053. g for
cuttings taken in .
31 .
-
0.40 , , , , '4., , ,o.ll
'a, , , '"
, 1 11
.. --6,..
-0.---&_ -.. 1 .~~
'r---r-----r---r----,-~___r--..__-__:__-____r--_r__-~.____,.
"J ,\"
CUlT INC t[S~T!I lCUl 1 . \
FIGURE 4. LOGISTIC REGRESSION OF PROBABILITY OF ROOTING AND
tNITIAL CUTTING LENGTH (CM). LN (PO / PJ) =-0.8J17 + 0.3369 (X),PO
= PR08AB III TY OF NOT ROOT ING I P3 = PROBAB I L I TY OF ROOT
ING,X= INITIAL CUTTING LENGTH. .
32
-
February. January cuttings had the lowest root fresh weight with
a mean sum of
0.028 g (Table 3). Collection dates were significantly different
with respect to root
dry weight which followed the same pattern as fresh weight.
There were no
significant interactions seen between mean fresh weights by
hormone level or by
source.
Significant differences were seen in root fresh weight in
hormone by collection
date and hormone by source by collection (Fig. 5). Examining the
mean plots for
the collection date by hormone interactions, the greatest root
biomass production
was seen in December with the control treatment. Among December
cuttings,
biomass production decreased as hormone level increased. After
December, IBA at
the 2500 ppm level resulted in greater fresh weight production
by treatment until
March when 5000 ppm IBA resulted in a slightly higher fresh
weight for the
cuttings. Rooting among cuttings receiving the 5000 ppm level
peaked in March,
whereas the control and 2500 ppm IBA peaked in December. Rooting
among
cuttings that received IBA at 10,000 ppm was low for all dates,
but increased
slightly in February.
Again, mean plots allow for comparison of the source by hormone
treatment by
collection date interactions. Cuttings from the Junction La
Junta source had the
greatest mean root fresh weight overall in December at the 2500
ppm IBA level.
The Willow Creek source cuttings gave the next highest values at
the 5000 ppm
IBA level in March, which was slightly higher than the no
hormone level in
December. The Cloudcroft source cuttings resulted in the lowest
values overall.
Best hormone level by collection date for this source was the
control treatment
33
-
Table 3. Means of root fresh weight (grams) for rooted cuttings,
by collection date.
Collection date Mean root fresh weight (g)
December 0.12454 A :',<
January 0.02805 B
February 0.05257 B
March 0.05514 B
". Means with the same letter are not significantly different.
Student-Newman-Keuls test, alpha = 0.05.
34
-
~ .25 1 ~ .Conlrol III I ~ 2500E I o .2 i ~ 5000 ~ I
I ~ 10000I..c 01 .15 ~
t t I I
I .1 i
i i I o
o .05c::: ,
FIGURE 5. MEANS OF ROOT FRESH WEIGHT (GRAMS) OF ALL CUTTINGS BY
COLLECTION DATE AND HORMONE LEVEL (PPM IBA).
35
-
in December (Fig. 6 a - c). Root dry weight also showed a
similar significant
interaction with source by hormone treatment by collection date.
The root dry
weight followed the same patterns as seen in the fresh weight
interaction, except for
the Willow Creek source. This source showed a lower mean dry
weight for the
control in December than the 5000 ppm IBA level, which is
reversed from the
response observed in the fresh weight data.
Primary root number
Root number was analyzed by using total number of primary roots.
Again lack
of normality was a problem in the analysis due to the large
number of missing
values (Table 4). Significant differences were seen among
collection dates, and in
the hormone level by source by collection date interaction.
Significant differences
were seen between cutting taken in December and January, but no
significant
differences were found among December, Feburary and March
cuttings, or
January, February and March cuttings. However, mean number of
roots did drop
for cuttings taken after December. The range test
(Student-Newman-Keuls) did
not indicate these in total number of primary roots by hormone
level or source.
This was probably due to unequal sample sizes.
The interactions of treatment by source by collection were
examined using mean
plots, and the patterns resemble the plots for fresh weight.
Cuttings from the
Willow Creek source showed the greatest number of primary roots
in the control
treatment in December, followed by a slightly lower level in
March with 5000 ppm
IBA. Cuttings from the Cloudcroft source showed a maximum in
March with 2500
36
-
0.' _ 0.1 \iii!!U ljM iili 0.4
i! 0.3
Ii)
- ............II 0.2 ........... !i ... .... .... .. .... "''"
............. ~ ... ~ .. __ ..~ .... _..... _..... ... !III 0 1 , _
_ _ : ,-= =_______ "-- ....... h
0:0 ..........n m ..:: ____ .....~_:
..:::.~...=.-...;;:::.:;:;..:-=-- --'~ OtCtllOtR JANUARY r DRUARY
IIMcn
0.8
_ 0.1
!!!u ~o.s
.)11 ili 0.4
l! 0.3 ! ~ 0.2
. 1;: 0.'
Cllll(CflO!C OAf(
B)
0.0 y-------------i t
omaER JAN\lART f[ SRUARY IIARCH
0
CCHICflO!! DII(
G)
..~","4
..............................
.. ~ ...... --_ .... - ... ---_. "'" t" - - -
IAHVAftT rrSRUARY
ca.UCllOli DAf(
FIGURE 6. MEAN ROOT FRESH WEIGHT (GRAMS) OF ALL CUTTING BY
COLLECTION DATE AND HORMONE LEVEL A} CLOUDCROFT, B} JUNCTI~NLA
JUNTA, C} WILLOW CREEK. . (CONTROL (NO 18A)=----:., 2,500 PPMI8A
=-, 5,000 PPM IBA =.------ .10, 000 PPM IBA =- , .
37
-
Table 4. Means of total number of primary roots of rooted
cuttings, by collection date.
Collection date Mean primary root number
December 0.6684 A *
January 0.1991 B
February 0.3673 AB
March 0.4615 AB
* Means with the same letter are not signillcantly
different.
Student-Newman-Keuls test, alpha = 0.05.
38
-
ppm IBA. The control treatment in December resulted in cuttings
with fewer
roots, but was the next best honnone level by collection date
combination. The
Junction La Junta source cuttings had considerably fewer primary
roots than
cuttings from the other sources. The best honnone level and
collection date
combinations were December and February cuttings receiving 2500
ppm IBA,
which gave similar results (Fig. 7 a - c).
Height ratio was the only covariate with a significant effect on
maXImum
number of primary roots. The negative slope estimate of -1.61
indicates that as
height ratio increased, number of primary roots decreased. Those
cuttings from
higher on the tree show a lower number of primary roots
intitiated.
Root length
Sum of root length for each cutting was analyzed using GLM (SAS
Institute,
1985). Significant differences were seen by collection date and
collection date by
honnone level by source using GLM. Using the
Student-Newman-Keuls range
test, no significant differences appeared for collection date.
This was probably due
to unequal sample sizes. However, examining the means, March
cuttings had a
mean length of 124.4 em, while 'Feb'ruary cuttings showed a mean
length of 24.0
cm. December cuttings showed a similar response to M arch
cuttings with a mean
of 118.1 cm. January cuttings had a mean root length of 38.1 cm
(Table 5). There
were no significant differences in root length among honnone
levels.
39
-
J.O A)
... il.O i1: 1.5 IJ I'l 1.0
~ ::: ,.-.....--........:
..:.:::"....,.~:--~.:.:.~~.:.:.~~.:.:~.:.~.:.- .. =~~: otCEIIa[R
JANUART rE8R~ART
J.O
orC[U~(R
l.O
2.S.. 8 '" 1.0
trA.lECl ION UAIE
c)
I
UAHCH
UARCH
i Ii'"' \!Ii 1.0 .i
'", ' ... , ........................
......--..........~.::.......................................
..............
O.S ----- ~,~----~~.~....~---.~.-..~...~.~----~~ 00 -. '"'..
------. ~---------~~~~======~=======T===-.=-=-=.~~~.~===:~
OCEUSR JAHUARY r(SRUART IIARCH
FIGURE 7. MEANS OF TOTAL NUMBER OF PRIMARY ROOTS OF ALL CUTT
INGS BY COLLECT 1ON DATE AND HORMONE LEVEL. A) CLOUDCROFT, 8)
JUNCTION LA JUNTA, C) WilLOW CREEK.
CONTROL (NO ISA) = -'- -'" 2,500 PPM IBA = , 5,000 PPM IBA=,
10.000 PPM IBA =--- .
40
-
Table 5. Means of sum of root length (cm) of rooted cuttings, by
collection date.
Collection date Mean sum of root length
December 118.10 A :I<
January 38.07 A
February 23.97 A
March 124.35 A
:I< Means with the same letter are not significantly
different.
Student-Newman-Keuls test, alpha = 0.05.
41
-
Mean plots allow for comparison of the collection date by
hormone level by
. source interacti-ons which were significant. The best
combination in terms of mean
sum of root length were cuttings from the Willow Creek source in
March with 5000
ppm lBA. In fact, cuttings receiving the 5000 ppm IBA level
resulted in greater
root length for all dates in the Willow Creek source, except for
cuttings taken in
February when there were no significant differences in root
length for any hormone
level. For the Cloudcroft source, the best hormone treatment by
collection date
. combination were cuttings taken in March and receiving 2500
ppm IBA. Cuttings
from the Junction La Junta source had less root length for most
dates and
hormone treatments. Among Junction La Junta cuttings, the
December-2500 ppm
IBA treatment resulted in the greatest root length (Fig. 8 a -
c).
Shoot activity
Shoot activity was analyzed similar to rooting response, shoot
elongation versus
no shoot elongation. Using a categorical model analysis,
significant effects were found by collection date" source and
hormone level by collection date interaction.
Collection date was highly significant with X2 = 118.36,
probability < O.OOOi.
The X2 value for source' was 10.31, probability = 0.0058.
Hormone level by
collection date interaction had a X2 value = 26:94, probability
= 0.0293.'
By collection date, probabilities for shoot elongation ranged
from 87~/O to 92%
in' December, January and February. In March and April shoot
elongation
decreased, followed by an increase in May to 81%. By source, the
Cloudcroft
source showed asignific"antly lower probability of shoot
activity, at 75%. Cuttings
42
-
100
100
600
!OO -----
a f: ...... OECtUOER
100
100
OrtEl/8U
100
100
600
c_
A)
-:, - - - ____ .. : ~~ ....--.......-.:-............__ h.:.~
JAHIJART rURUART \l.f.RCH
ta.LECIIOII DAlt
JAIIUAIlT
ta.tttliOll QAI(
".'
B)
"
... ,.
"
........ ...-------... --... - - - - ..
rr2RUART IWICH
L!)
FIGURE 8. MEANS OF SUM OF ROOT LENGTH OF ALL CUTTINGS BY
COLLECTION DATE AND HORMONE LEVEL. A) CLOUDCROFT,S) JUNCTION LA
JUNTA, C) WILLOW CREEK. CONTROL (NO IBA) :::: - --,2500 PPM IBA =
,5,000 PPM ISA =-..-. __ . j 10,QOO PPM ISA =---.
43
-
from the Junction La Junta source and the Willow Creek source
had shoot activity
probabilities of 80% and 84%, respectively (Fig. 9). The hormone
level by
collection interaction also shows the drop of shoot activity in
March and April.
There appears to be some alteration of shoot activity with
hormone level, but
overall trends do not change (Fig. 10).
... Again logistic regression was used to analyze the relation
between shoot activity
and height ratio, initial caliper and initial fresh weight.
Significant relations were
found between height ratio and shoot activity over all data
sets, and for cuttings
from the Cloudcroft source. With a positive slope estimate
estimate of 0.779 (X2
= 5.12, probability = 0.0236), as height ratio increases, the
probability of shoot
activity decreases. In other words, the sho.ots located higher
on the tree have a
lower probability of shoot elongation for all collection dates
and hormone levels.
In addition, for the May collection, a significant interaction
between cutting length
and shoot activity was found, with a negative slope estimate of
-0.246 (X2 = 6.58,
probability = 0.0103). As cutting length increased, the
probability of shoot
activity decreased, for the May collection.
Shoot analysis
Final cutting measurements were also taken on the shoot
material. These data
wer~ analyzed in a similar manner to the root data using GLM
(SAS Institute,
1985). Again, the April and May collections were omitted from
the analysis due to
low rooting success. Only 2 of the variables, final cutting
length and final fresh
weight, could be used in the analysis. The final caliper
measurement was of little
44
-
PEHCENT
SOURCE
FIGURE 9. PRO[3AB III TY OF curT f NGS TO BRE AK I3UD AF I EH
IIM?VF. S I (PERCENT OF TOTAL CUTTINGS BY SOURCE).
45
-
j'
.j- . ... /.~.' , . ..,/.-'
~. ~ .~..-;...: ~ ~ ~.~ .........
19r------r-___-,--___-,--___-.,.-___-,. If., I
F I CURE 10. PROBABI LI TY OF CUTT INCS TO BREAK BUD AFTER
HARVEST,
PERCENT OF TOTAL CUTTINGS, BY COLLECTION DATE AND HORMONE
LEVEL.
CONTROL (NO ISA) =----- ,2,500 PPM ISA =-5000 PPM ISA =
........... , 10, 000 PPM ISA = - - -.
46
-
value due to extensive stem rot of the base of the cuttings,
even in some of the
cuttings which rooted.
Cutting length
The fmal cutting length was measured at the end of the study.
Significant
differences were found among collection dates (F(l, 154) = 3.46;
p = 0.0170) and
in the collection date by source interaction (F(l, 154 = 3.97; p
= 0.0008). In
addition, the co variates were used for ctnalysis and
significant linear relations were
found in initial cutting fresh weight (F(l, 431) = 17.26; P <
0.0001) and in initial
cutting length (F(I, 431) = 23.66; p < 0.0001).
Using the Student-Newman-Keuls test, no significant differences
were seen
between cuttings collected in December and February with mean
lengths of 10.09
em and 10.16 em, respectively. . However, the differences
between the
December/February cuttings and J(l.lluary/March cuttings were
significant. There
was no significant difference between the January and March
collections with mean
lengths of 10.53 em and 10.49 em, respectivdy (Table 6),' This
is consistent with
means of initial cutting length. January and March mean cutting
lengths were
longer than were December and February cuttings.
Mean plots were used to examine the source by collection date
interaction with
fmal cutting length (Fig. 11). Cuttitjgs from the Cloudcroft
source showed the
shortest length for all dates .. The mean length for cuttings
from all sources were .. '
\\1thin 0.2cin in December. The \Villow Creck source tended to
have the longest
, 47
-
Table 6. Means of cutting length (cm) of all cuttings, by
collection date.
Collection date Means of fmal Means of initial cutting length
(cm) cutting length (cm)
December 10.09 B * 9.26
January 10.54 A 9.70
February 10.16 B 8.95
March 10.49 A 9.43
* Means with the same letter are not significantly
different.
Student-Newman-Keuls test, alpha = 0.05.
48
-
II .
11
11.1
11. ,
11.1 i! 11.1
11.1 .~ 11.7 a l't ,/ ~ . :::; '"
1.1
I. t
'.7
---------- .... --------. ----. --.... _ ... ----..,-_ ....
--
I.r---------------~--------------~~------------~ lUVUl 1(IIU.,1
IH(M
CIllUCIlOll OAlE
FIGURE 11. MEANS OF FINAL CUTTI NG LENGTH (CM) BY' COLLECT ION.
DATE AND SOURCE. CLOUDCROFT =. - - - JUNCT ION LA JUNTA = - , WI
LLOW CREEK =.-.-----
49
-
cutting length means for all collections and showed the most
variability. Cuttings
from the Junction La Junta source was intermediate and remained
fairly constant
for all collection dates. The greatest spread in mean cutting
lengths was in March.
with the Willow Creek source cuttings increasing to the highest
level.
Fioal cutting weight
For fmal fresh weight significant differences were found among
collection dates
(F(l, 154) = 33.45; p < 0.0001), for the collection dates by
source interaction (F(l,
154) = 2.96; p = 0.0081) and the collection date by hormone
level combination , ' '.
(F(l, 154) = 3.70; p = 0.0002). Of the covariates used with the
fmal shoot fresh
weight, only initial fresh weight of the cutting was significant
(F(l, 431) = 99.37; p
< 0.0001). Using the mean sums of cutting fresh weight with
the
Student-Newman-Keuls test, mean weights for December and January
cuttings
were not different. March mean fresh weight for cuttings was
significantly less with
a value of 4.35 g. The::; mean fresh weight for cuttings taken
in February was also
significantly less than all other dates at 3.91 g (Table 7).
Mean plots of fmal shoot fresh weight were used to look at. the
source by
collection date interaction. All the sources follow a similar
trend for all collec~ion
dates (Fig. 12). The greatest spread in mean weights is seen
among December
cuttings by source. The Cloudcroft source cuttings generally had
the highest mean
fresh weight for all collections. Cuttings from the Junction La
Junta source
exhibits the next highest values for most collections followed
by the Willow Creek
source. A noteworthy point is that cuttings from the Cloudcroft
source shows the
50
-
highest mean sum in December, dropping in January and February
and climbing in
March. On the other hand, the cuttings from the other 2 sources
show the highest
values in January, and dropping in February and increasing again
in March.
In looking at the mean plot for the collection date by hormone
level interaction
on fmal cutting fresh weight it appears as if the December date
is the only time
where the interaction is highly significant (Fig. 13). Cuttings
from the control
result in the highest mean fresh weight in December. IBA at 2500
ppm shows a
constant mean fresh weight for cuttings taken in December and
January.
Beginning in January cuttings from all the treatments follow the
same trend and the
order remains constant. Cuttings receiving IBA at the 5000 ppm
level result in the
highest mean, followed by 10,000 ppm, 2500 ppm and the control.
Vttlues for all
cuttings drop in February followed by an increase in March.
51
-
Table 7. Means of shoot final fresh weight (grams) of all
cuttings, by collection date.
Collection date Mean cutting fresh weight (g)
December 4.56 A'"
January 4.62 A
February 3.91 C
March 4.35 B
'" Means with the same letter are not significantly
different.
Student-Newman-Keuls test, alpha = 0.05.
52
-
--- ---- ---1.1 -----1,1 _..........;~.~ _._-_._--_..--
.......~............., .................~...:.~...............:.:..
~
j
~ 1.1 I.'
I 1
I .. 'r-------~-------_,_------___r
ClllCllON DAft
fIGURE 12. MEANS Of fiNAL fRESH WEIGHT (GRAMS) Of CUTTINGS BY
COLLECTION DATE AND SOURCE. CLOUDCROfT =-----., JUNCTION LA JUNTA =
WI LLOW CREEK =..........,..I
53
-
a 1.1 iii 1.1
iI ... ; l.1 ;: 3.1
3. I
l.l
............... "'~ ....
Ui------.....,.---,---------.-----__--r om~.u IUUltT I(tRQU!
IlRtM
aU(CIIOH Oll(
FIGURE 13. MEANS OF FINAL FRESH WEIGHT (GRAMS) OF CUTTINGS BY
COLLECTION DATE AND HORMONE LEVEL. CONTROL (NO ISA) =------. 2I 500
PPM ISA = 5.000 PPM ISA =.............. 10 .000 PPM ISA =-.- .
54
-
DISCUSSION
Although overall rooting success was low, it is possible to root
stem cuttings
from 10year-old blue spruce. Collection date was the singie
factor significant for
almost every response variable analyzed. Differences in rooting
capacity were
. detected among the geographic sources in the study. From the
results, cutting from
the Cloudcroft source rooted most often. Rooting response
differed only slightly
among cuttings from the Willow Creek and Junction La Junta
sources. Comparing
differences in stock plant height among sources, there was
little difference between
the mean heights of the sources selected. There is no clear
indication as to the
cause of the source variation in rooting success. The
differences may be due to
inherent genetic differences or to other factors.
In addition to overall so.urce differences in rootirlg success,
there were
differences seen within sources by tree. Cuttings from some
trees did not root at
all, and others rooted up to 50%. However, because all cuttings
from each tree
received the same hormone level it is possible that if those
trees not rooting had
been assigned to another hormone level, they might have rooted.
However, other
studies have shown similar results indicating . genotypic
variation in rooting
percentages with white pine (Williams, 1987), Fraser fir (Miller
et al., 1982) and
black spruce (Phillion 1982).
55
-
Collection date
The best collection time was December followed by February. The
drop in
rooting seen in cuttings taken in January was unexpected. The
expected rooting
percentage was somewhere between the 15% in December and the 13%
in
February. One explanation is that January was not a favorable
time for root
initiation in stem cuttings. Perhaps there was some difference
among December,
January and February which favored root initiation among
cuttings taken in
December and February but not.in January. The lower rooting
response observed
in cuttings collected in January may be correlated to factors
which are not
season-dependent, for example, length of cuttings taken. The
cuttings harvested in
January were longer than cuttings taken in December and
February.
Except for the drop in January, it appears as if the best time
to take blue spruce
stem cuttings is during the winter months, after the chilling
requirement has been
met (as determined by budbreak in the greenhouse). Rooting
actually dropped off
among cuttings collected in the late winter- to early spring
months which had been
recommended by some researchers (Hanover 1975). It should be
mentioned that it
is possible that the best collection date occurred before the
study was begun. These
results differ from studies indicating Norway spruce roots well
in April and May
(Girouard, 1975). However, Fraser fir, as well as other conifer
species, roots well in
January and February (Hinesley and Blazich, 1984). Thimann and
Delisle (1942)
found blue spruce rooted best in April, with some rooting in
November. But Iseli
and Howse (1981) have more consistent rooting with blue spruce
in January.
56
-
Hormone level
The be.st treatment for rooting success was the control followed
by 2500 ppm
IBA. There was TIttle difference between the control and IBA at
the 2500 ppm
level. In another study with blue spruce cuttings taken in
March, there were no
differences in rooting responses of cuttings from lO-year" trees
when treated with no
hormone, 2500 ppm IBA or 5000 ppm IBA. Cuttings from I-year
seedlings
however, .while rooting at higher levels overall, only had 100%
rooting success with
5000. ppm IBA. Cuttings from IS-year old trees on the other
hand, showed the
highest rooting response (29%) when treated with 10,000 ppm IBA
(Wagner, 1987;
unpublished data). Although the collection date by hormone
treatment interac~ion
was not significant in terms of rooting success, examination of
the raw data
indicates that the control treatment in December and 2500 ppm
IRA in February
are the best treatment by collection date combinations. These
results differ fom
other blue spruce studies indicating that higher levels of
auxins. are necessary to
promote rooting (Hanover, 1975; Struve, 1982)
Cutting ~haracteristics
In addition, it appears as if the shorter cuttings are more
likely to root than are
the longer cuttings in blue spruce. This may be in part be
related to overall stock
plant condition which favors shoot extension to the detriment of
rooting capacity.
Farrar and Grace (1942) found some di~erences in rooting of
Norway spruce.
They round shorter c~ttings may have higher success in rooting,
but that
shortening longer cuttings was of no benefit. Fraser fir,
however, showed no effect
57
-
of cutting length on rooting percentages, but longer cuttings
tended to initiate more
and longer roots (Miller et al., 1982)~ The Cloudcroft source
had the shortest
cuttings overall and also the highest rooting success. The
question arises whether
rooting success is due to the growth fonn which involves short
terminal shoots on
the branches. Or is the rooting success seen in this study due
to an inherent
rooting capacity and the cutting length and root initiation
relationship is merely
coincidental.
The vertical position of the cutting on the tree made some
difference, which is in
agreement with other published results. Cuttings from the lower
portion of the tree
were more likely to root. Phillion and Mitchell (1984) found
differences even in
juvenile black spruce cuttings. Cuttings from the lower two
thirds of the crown
rooted better. There was no significant difference found between
cutting stem
caliper and cutting fresh weight and the probability of root
intitiation in this study.
Root yroduction
Several factors significantly affected root quality. Collection
date was significant
for all root characteristics analyzed. As discussed above,
rooting success was
highest among cuttings taken in December followed by February.
December
cuttings also showed the highest root biomass production,
followed by March.
Maximum number of primary roots was highest in December
cuttings, followed by
February, and root length was greatest in March cuttings,
closely followed by
cuttings taken in December. Overall, rooting percentages were
relatively high for
cuttings taken in February, the root quality was less optimum
than in December.
58
-
Considering all the factors of rooting and root quality, an
overall recommendation
would be to take blue spruce cuttings in December.
Root fresh weight was the only root characteristic to exhibit a
significant
collection date by honnone level interaction. Root fresh weight
changed with
honnone level as the season progressed. In December the highest
biomass
production was seen with the control level. Cuttings made in
January and
February showed increased production with 2500 ppm IBA, and
March cuttings
showed the highest root fresh weight with 5000 ppm IBA.
The other interaction of importance for all the root
characteristics is the source
by honnone level by collection date interaction. Looking at the
interactions over
all dates and treatments, for both the Cloudcroft and Willow
Creek sources, the;:
best treatment and date combination is the December collection
with the control
treatment. The root characteristics of cuttings from both
sources in December, . .
with the control, were relatively high, and rooting success was
also high (45% and
40%, respectively). For cuttings from the Cloudcroft source, the
March collection
at 2500 ppm IBA also gave high root number, length and fresh
weight, but rooting
was less at 20%. Willow Creek source cuttings also showed high
values for root
characteristics in March at 5000 ppm IBA, but rooting was only
S>/o. Showing a
somewhat different response was the Junction La Junta source.
The best treatment
by collection date combination in tenns of root quality was
cuttings taken in
December at 2500 ppm IRA. However, rooting percentages were low
at 10%. In
terms of rooting success, the March collection and the control
treatment gave the
best results with 25% rooting, whereas root quality was less
than optimum.
59
-
Shoot activity
Shoot elongation may possibly be related tQ root intitiation.
Haissig (1982) has
shown with jack pine that removal of the te1:rn.inal bud reduces
rooting responses.
The occurrence of budbreak in the greenhouse indicates two
things: first, it
indicates whether or not chilling requirements have been met for
budbreak. As
mentioned earlier, many conifers will not initiate roots until a
certain level of
chilling has occurred. The second is an in.dication of internal
nutrient status.
When carbohydrates and nutrients become limiting. budbreak is
less likely to occur.
Comparing rooting success with shoot activity (or budbreak), in
this study, the
highest levels of shoot activity are correlated With higher
levels of root intitiation.
Later in the season, e.g., March and April, the decrease in
shoot activity could be
an indication of a change in internal carbohydrate levels, which
can reduce the
capacity for root initiation, as well as changes in hormone
levels.
There was a correlation between height ratio and shoot activity.
Shoot activity
decreased as cutting height increased, whicri is the same
relation seen with root
intitiation. Cuttings from the upper part of the tree were less
likely to initiate roots
and intiated fewer primary roots. The result~ from this study do
seem to indicate
that there is some relationship between bud activity and root
initiation. However,
Miller et al. (1982) found in Fraser fir that Cutting length and
bud activity were
inversely related. However, this reduction "in activity was not
correlated to root
initiation.
60
-
Final shoot characteristics
As mentioned earlier, the fmal shoot characteristics were
significant in terms of
collection date, and initial length and weight. Final cutting
length was highly
significant in terms of initial cutting length, which was
expected. Looking at the
fmallength over collection date, the longer cuttings were found
in Janaury and
March, with the shorter cuttings found in December and February.
This
corresponds to the higher rooting success in December and
February. It is possible
that through chance, longer cuttings were taken in January which
could explain
the drop in rooting success. The relation between final shoot
length and collection
date agrees with the interaction seen between initial cutting
length and root
initiation.
Final fresh weight of the cuttings was significantly related to
initial fresh weight,
collection date, collection date by sour~e and collection date
by treatment. There is
no clear indication of a relationship between rooting success
and final shoot fresh
weight of the cuttings. Weights are highest in December and
January, dropping in
February and March. As mentioned previously, there was no
significant
interaction between rooting and initial fresh weight.
Conclusions
In summary, the single factor which overrode every variable
examined was
collection. date. Hormone treatment altered somewhat the
inherent rooting
capacity, but could not completely compensate for non-optimum
collection date.
61
-
As expected, some trees and sources are more likely to root than
others. Within a
tree, cutting position and length do appear to influence rooting
success. Overall, a
general recommendation for rooting of lO-year-old blue spruce
would be to take
short cuttings from the lower portion of the tree in December
with no hormone
treatment. From the results, lO-year-old blue spruce does not
appear to be a
species which would be easily mass propagated with field-grown
stock plants.
However, on a limited scale, such as propagation of superior
trees for a breeding
program, it would be possible to successfully propagate clones
en masse but
perhaps with a narrowing of the genetic base.
62
-
LITERATURE CITED
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Brix, H. and H. Barker. 1913. Rooting studies of Douglas-fir
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Cameron, B.J. and G.V. Thomson. 1969. The vegetative propagation
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Clark, J.R. 1981. Juvenility and plant propagation. Proc. Inter.
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