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In summary, the results of this study provide information
to nursery producers, extension agents and nursery inspectors
on the symptoms associated with A. ricini infection of E. milii
The awareness of A. ricini in E. milii in bedding plant nursery
will assist in reducing the spread of this fungus through retail
garden stores to the public growers.
Literature Cited
Ellis, M. B. 1971. Dematiaceous Hyphomycetes. Commonwealth Mycological
Institute, Kew, Surrey, England. M. F. Clark and A. N. Adams. 1971.
Figure 10. The Amphobotrytis state of Sclerotinia ricini showing elongated
sclerotia, 3-9 mm long, occasionally up to 2.5 cm.
Proc. Fla. State Hort. Soc. 113:165-169. 2000.
A PEER REVIEWED PAPER
RESPONSE OF SPATHIPHYLLUM CULTIVARS TO CHILLING TEMPERATURES
L. Qu, J. Chen* R. J. Henny, C. A. Robinson,
R. D. Caldwell and Y. Huang
University of Florida, IFAS
Mid-Florida Research and Education Center
2725 Binion Road
Apopka, FL 32703
Additional index words. Chilling injury, foliage plants, peace lily.
Abstract. The response of 15 Spathiphyllum cultivars after 2, 5
or 10 days of exposure to chilling temperatures of 3.3, 7.2,10
or 11.1 C was evaluated using rooted three-month old tissue
culture derived plants. Chilling injury at 3.3 and 7.2 C varied
among cultivars from slight leaf necrosis to plant death;
younger leaves were more resistant to chilling than older ones
with the exception of one cultivar. At 10 or 11.1 C, no visible
tissue breakdown occurred. However, small growth indices
and low quality ratings were indicative of otherwise invisible
injury at these temperatures. Such invisible injury could be
wrongly diagnosed as insufficient fertilization or other improp
er cultural practices. These findings suggest that genetic dif
ferences in chilling resistance exist among Spathiphyllum
cultivars and can be used as a basis for cultivar selection.
The genus Spathiphyllum includes 36 species of evergreen
rhizomatous perennials, commonly called peace lily, origi
nates from tropical forest habitats (Huxley, 1994). Because of
its elegant white or creamy spathes and deep green foliage,
Florida Agricultural Experiment Station Journal Series No. R-07717.
*Corresponding author.
Spathiphyllum has become one of the most popular foliage
plants in the ornamental industry. Ranked as a top-seller in
the market, there are currently more than 50 species and/or
cultivars produced in Florida.
Due to its tropical rain forest origin, Spathiphyllum is natu
rally sensitive to chilling temperatures (2-10°C, as defined by
Lycons, 1973). Marousky (1980) found that a one-day expo
sure of Spathiphyllum 'Clevelandii' to 10°C resulted in notice
able leaf injury characterized by necrotic patches along leaf
margins. Chilling injury can cause severe losses in production
if heating systems are not available during winter and early
spring in Florida. Chilling injury may also occur during Spath
iphyllum shipment, retail display and interior decoration.
Since Spathiphyllum is grown for its aesthetic appearance, any
damage on leaves or flowers could greatly reduce its orna
mental value in the market place.
In an attempt to improve the resistance of foliage plants
to chilling, we have been exploiting the genetic potentials of
existing cultivars to chilling through a systematic evaluation.
Previously, we were able to identify Aglaonema cultivars that
can withstand 1.7°C, whereas sensitive ones were injured at
12°C (Henley et al., 1998; Chen et al., 1998). Resistant culti
vars are important not only to growers in production, but also
have been incorporated into our research program for culti-
var improvement.
So far, no report has addressed cultivar differences of
Spathiphyllum in resistance to chilling temperatures and no re
sistant cultivars have been identified. The objectives of this
study were to evaluate cultivar responses to chilling and iden
tify resistant ones for the industry and for our subsequent
breeding program.
Proc. Fla. State Hort. Soc. 113: 2000. 165
Materials and Methods
Fifteen cultivars of Spathiphyllum: Annette, Connie, Deb
bie, Little Angel, Lynise, Mini, Viscount, Classic Viscount,
5598, 0597-3, UF474-1 UF576-14, Petite, Starlight and Vicki
Lynn, which were tissue culture derived plants rooted in 72-
cell trays in a shaded greenhouse, were obtained from local
tissue culture laboratories. All cultivars were three-month old
with each plug (cell) containing three plants. Plants were ac
climatized in a shaded glasshouse under a maximum photo-
synthetic active radiation (PAR) of 200 umol-nr2-^1 (about
1,250 foot candles), a temperature range from 18°C to 32°C
and 65% relative humidity for a week before being exposed
to the chilling temperatures.
Two chilling Experiments were conducted. In Experi
ment 1: plugs of eight cultivars were chilled at three temper
atures, 3.3, 7.2 and 11.1°C (38, 45 and 52 °F respectively) for
5 or 10 days. In Experiment 2: plugs of 11 cultivars, including
four cultivars used in Experiment 1, were exposed to 3.3, 7.2
and 10°C (38, 45 and 50°F) for 2 or 5 days. Both Experiments
were arranged in a completely randomized design with seven
and five replications (one plug per replication) per treatment
for Experiments 1 and 2, respectively. Plugs of cultivars re
mained in the shaded glasshouse as controls.
Walk-in coolers (3 m x 3 m) were used as chill chambers
where a PAR of 48 (unol-nr^s1 (about 300 foot candles) was
provided by cool-white fluorescent lamps for 12 h daily.
Chamber temperatures were set at respective temperatures
and allowed to stabilize for 24 hours before beginning the Ex
periment. All plants were watered thoroughly before placing
in the chambers, and no additional watering was provided
during the chilling periods.
After chilling, the plants were removed from the cham
bers. The chilling treated and control plants from Experi
ments 1 and 2 were respectively potted into 15.1-cm (6-inch)
and 10.1-cm (4-inch) pots (one plug per pot) containing Ver-
go Container Mix A (Verlite Co., Tampa, FL). Potted plants
were then grown in the shaded glasshouse for chilling re
sponse evaluation.
Chilling injury measurements were recorded 3 days after
each chill treatment. These included the percentage of dam
aged leaf area and the number of dead plants. For damaged
leaf area measurements, four top fully uncurled leaves were
sampled from the main shoot of each plug. The leaf area was
determined non-destructively by placing the leaf blade
against a transparent grid marked in 0.5-cm square units. Per
centage of damaged leaf area was calculated based on the pro
portion of total squares covered by the damaged leaf area
versus total squares covered by the entire leaf.
Long term chilling effects were evaluated 45 days after
treatment for plants chilled in Experiment 1 and 20 days after
treatment for plants in Experiment 2 by measuring the growth
index and plant quality. Growth index (GI) = [(plant width 1
+ plant width 2) -5- 2] x plant height (Beeson, 1992; Stamps and
Evans, 1999). Plant width 1 is defined as canopy width at widest
point and width 2 is measured after a 90° rotation of the pot.
In reference to the Nursery Plant Grading Standards (Florida
Department of Agriculture and Consumer Services, 1997) as
well as methods described by Conover et al. (1982) and Poole
et al. (1986), quality rating was based on the following scale: 5
= no necrotic damage with excellent leaf color, 4 = no necrosis,
but slight leaf discoloration, 3 = 1-20% total leaf necrosis, 2 =
more than 21% total leaf necrosis, and 1 = plant dead.
After testing the normal distribution of residuals from
data of quality rating, data of growth index and quality rating
were analyzed using the ANOVA procedures of the SAS pro
gram (SAS Institute Inc., Cary, NC).
Results and Discussion
Significant differences in chilling responses were found
among the Spathiphyllum cultivars. Responses such as partial
or whole leaf necrosis were observed among cultivars evaluat
ed at 3.3 and 7.2°C but not at 10 or 11.2°C. The percentage
of damaged leaf area among cultivars chilled in Experiment
1 at 3.3 and 7.2°C is presented in Fig. la and lb respectively.
Figures 2a and 2b show cultivar responses to 3.3 and 7.2°C
respectively in Experiment 2. The damaged leaf area at 3.3°C
varied from less than 5% for '5598' and '0597' to 100% for
'Mini', 'UF576-14' and 'US474-1' for the same chilling dura
tion. 'Mini', 'UF576-14' and 'US474-1' died 3 to 5 days after
chilling at 3.3°C.
Although physiological mechanisms underlying the cause
of chilling injury are still not completely understood, accumu
lated evidence has suggested that chilling stress affects various
functions of plants, including membrane fluidity, enzyme
conformation and activity, water and nutrient balance, photo-
synthetic and respiratory functions (Graham and Patterson,
1982; Taiz and Zeiger, 1998). All of these effects probably de-
Cultivar
100 -I
Cultivar
Figure 1. The percentage of damaged leaf area of Spathiphyllum cultivars
chilled at (a) 3.3°C and (b) 7.2°C for 5 or 10 days (Experiment 1). Data were
collected 3 days after the chilling treatments.
166 Proc. Fla. State Hort. Soc. 113: 2000.
100 i
80-
60-
40-
20
0
(9 2d
■ 5d
Cultivar
60
40-
20
0
Q 2d
■ 5d
Cultivar
Figure 2. The percentage of damaged leaf area of Spathiphyllum cultivars
chilled at (a) 3.3°C and (b) 7.2°C for 2 or 5 days (Experiment 2). Data were
collected 3 days after the chilling treatments.
pend on a common primary mechanism involving in loss of
membrane function due to chilling (Raison and Orr, 1990).
When the temperature drops below a critical level, membranes
will solidify and become less fluid. As a result, the activities of
the integral membrane proteins such as H+-ATPases, carriers
and channels as well as metabolic processes of cells no longer
function normally. Consequently, the lower the temperature
for a given period or the longer the time at a given tempera
ture, the greater and more extensive the injury (Lyons, 1973).
As anticipated, prolonged exposure of Spathiphyllum culti
vars to the chilling temperatures caused more damage than
shorter periods of exposure at respective temperatures (Figs.
1 and 2) and such damage was more pronounced at 3.3°C
than at 7.2°C. This chilling response pattern was also previ
ously demonstrated by Marousky (1980) in Spathiphyllum and
Dracaena, suggesting that damage can be lessened if preventa-
tive actions are taken to reduce either the severity or the du
ration of chilling, or both, during production.
Most evaluated cultivars followed the chilling response
pattern as discussed above, but some cultivars appeared to re
spond to chilling differently. For example, '5598', '05973'
and 'Petite' had a similar degree of injury at both 3.3°C and
7.2°C (Figs. 1 and 2), indicating that critical chilling temper
ature for each cultivar is different. This difference could be
due in part to the membrane fatty acid composition of culti
vars. Membrane lipids from chilling resistant plants often
have a greater proportion of unsaturated fatty acids than
those from chilling sensitive plants (Lyons, 1964). Studies
from Williams et al. (1988) and Palta et al. (1993) further
demonstrated that the activity of desaturase enzymes increas
es and the proportion of unsaturated lipids rises during accli
mation to chilling temperatures. This modification allows
membranes to remain fluid at the chilling temperature and
sustains normal metabolic functions of cells. Thus, further re
search to determine whether unsaturated fatty acids play a
protective role against chilling in these resistant Spathiphyllum
cultivars is warranted.
Chilling injury initiated from leaf tip and edge and pro
gressed inwardly, with the damaged leaf area becoming nec-
rotic and dry. As was observed in Aglaonema (Chen et al.,
1998), leaves of different maturity responded to chilling differ
ently. The more mature leaves were more sensitive to chilling.
Unfurled leaves had the greatest chilling resistance with the
exception of 'UF474-1'. When this cultivar was chilled at 7.2°C
for two days, the unfurled leaves showed more damage than
the mature leaves. The physiological basis for the more chill
ing resistance of younger leaves than mature ones is not
known. One possible explanation could be due to the nutrient
status, particularly K, which is known to be actively involved in
the osmotic adjustment of plant cells and is present in much
more abundance in young leaves than old and mature ones.
Chilling injury was not immediate in all cultivars at 10 or
11.1°C. However, chilling effects were evidenced during the
post-treatment growth as indicated by smaller plant growth
indices than control (Table 1). The growth indices of plants
treated at 10°C for 2 or 5 days (Experiment 2) were not signif
icantly different from control (Table 2). This could be due to
the short duration of chilling, or the short recovery time.
Since the growth index was measured 20 days after chilling,
Table 1. Growth index2 of Spathiphyllum cultivars 45 days after exposure to three chilling temperatures for 5 or 10 days (Experiment 1).
Treatment
<°C)
Control
11.1
7.2
3.3
Day
0
5
10
5
10
5
10
5598
370.5 ax
223.8 b
200.2 b
163.6 b
151.5 b
191.5 b
90.9 b
Annette
283.1 a
227.8 ab
181.7 abc
137.6 be
72.3 cd
141.1 be
0dw
Connie
502.9 a
332.9 b
308.5 b
120.8 c
77.4 c
100.0 c
0c
Cultivar
Debbie
276.3 a
249.9 ab
200.6 be
90.4 de
40.5 ef
150.3 cd
Of
Little Angel
265.5 a
215.3 ab
199.5 abc
118.7 bed
92.5 cd
136.9 bed
52.9 d
Lynise
474.8 a
424.9 a
387.1 a
113.9 b
31.3 b
122.7 b
0b
Viscount
350.6 a
301.9 ab
181.5 be
204.7 be
92.5 d
145.6 c
Oe
Mini
379.8 a
194.5 b
202.3 b
0c
0c
0c
0c
'Growth index (cm2) = [(plant width 1 + plant width 2) -*- 2] x plant height.
^Control temperature ranging from 18 to 32°C.
"Mean within columns followed by the same letter are not significantly different (LSD, P< 0.05).
wPlants died.
Proc. Fla. State Hort. Soc. 113: 2000. 167
Table 2. Growth index' of Spathiphyllum cultivars 20 days after exposure to three chilling temperatures for 2 or 5 days (Experiment 2).
Treatment
(°C)
Control?
10.0
7.2
3.3
Day
0
2
5
2
5
2
5
5598
223.9 ax
230.6 a
168.0 abc
179.8 abc
190.9 abc
131.2 c
143.6 be
Connie
131.6a
117.2 a
133.3 a
109.4 a
86.3 a
94.4 a
96.9 a
Little
Angel
105.8 a
100.6 ab
88.7 ab
90.3 ab
69.8 ab
64.1b
75.8 ab
Lynise
154.1 a
136.2 ab
169.2 a
122.3 ab
85.1 c
75.2 be
41.0 c
0597-3
195.7 a
170.1 a
173.1 a
163.8 a
157.9 a
143.0 a
119.9 a
Cultivar
UF474-1
79.9 a
65.1 ab
49.3 b
23.7 c
0dw
Od
Od
UF576-14
113.3a
103.9 a
78.9 a
80.0 a
36.6 b
0b
0b
Classic
Viscount
113.6 a
111.9 a
113.4 a
104.7 a
111.0a
104.2 a
86.2 a
Petite
78.1a
76.3 a
79.3 a
63.7 a
63.9 a
56.0 a
56.9 a
Starlight
134.7 a
114.0 a
134.5 a
112.9 a
91.6 ab
80.3 b
82.6 b
Vicki
Lynn
210.9 a
187.2 ab
170.9 ab
160.5 abc
140.3 abc
102.6 be
101.3 c
'Growth index (cm2) = [(plant width 1 + plant width 2) -5- 2] x plant height.
^Control temperature ranging from 18 to 32°C.
xMean within columns followed by the same letter are not significantly different (LSD, P< 0.05).
wPlants died.
the time for distinguishing growth difference may have been
too short. In addition, the overall plant quality rating for 10
or 11.1°C treatments was slightly lower than the control
(Tables 3 and 4). Such latent effects were probably caused by
chilling-induced temporal inactivation of enzymes, inhibition
of photosynthesis and slower respiration (Levitt, 1980; Wil
son, 1987), rather than by the low light intensity in the chill
ing chambers. Our interiorscape studies reveal that vegetative
growth of Spathiphyllum is not greatly affected by short-term
low light (such as 48 inmol-m^s1) for 30 days. The latent ef
fects may at least in part explain why Spathiphyllum growth in
winter and early spring decreases during production even
though heating is provided. Implementing appropriate mea
sures to avoid or minimize the chilling could improve Spathi
phyllum production.
Chilling can affect both shoots and roots (Lyons, 1973;
Taiz and Zeiger, 1998). Since the entire pot system (shoot,
roots and medium) was subjected to chilling simultaneously
in this study, probable root chill damage might have occurred
as well. This differs from normal cultural practices where a
temperature gradient exists within the pot system, but it du
plicates chilling shipping experience. Therefore, chilling in
jury observed in shoots might have been directly associated
with the chilling of the shoots, roots or a combination of the
two. The degree of sensitivity attributed to roots or shoots sep
arately is not known.
Table 3. Quality rating' of Spathiphyllum cultivars 45 days after exposure to three chilling temperatures for 5 or 10 days (Experiment 1)
Treatment
(°C)
Control
11.1
7.2
3.3
Day
0
5
10
5
10
5
10
5598
4.0 a*
3.8 a
3.6 a
3.1 a
2.6 ab
3.0 ab
1.9 b
Annette
4.3 a
4.1 a
3.0 ab
2.8 be
2.0 cd
2.8 be
1.0 d
Connie
4.7 a
4.1a
3.6 ab
2.4 c
1.9 cd
2.1 c
1.0 d
Debbie
4.0 a
4.3 a
3.3 ab
2.0 be
2.0 be
3.0 ab
1.0 c
Cultivar
Little Angel
4.5 a
3.6 ab
3.6 ab
2.8 be
2.0 c
2.6 be
1.9 c
Lynise
4.0 a
4.3 a
3.3 ab
2.0 be
2.0 be
3.0 be
1.0 c
Viscount
4.8 a
3.0 b
2.6 be
2.4 be
1.8 cd
2.4 be
1.0 d
Mini
3.0 a
2.0 ab
2.3 ab
1.0b
1.0 b
1.0 b
1.0 b
'Quality rating was based on the following scale: 5 = no necrotic damage with excellent leaf color, 4 = no necrosis, but slight leaf discoloration, 3 = 1 to
total leaf necrosis, 2 = more than 21% total leaf necrosis and 1 = plant dead.
^Control temperature ranging from 18-32°C.
xMean within columns followed by the same letter are not significantly different (LSD, P< 0.05).
Table 4. Quality rating7 of Spathiphyllum cultivars 20 days after exposure to three chilling temperatures for 2 or 5 days (Experiment 2).
Treatment
(°C)
Control
10.0
7.2
3.3
Day
0
2
5
2
5
2
5
5598
4.2 abx
4.7 a
3.5 ab
4.7 a
3.6 ab
3.6 ab
3.1b
Connie
4.3 a
3.8 ab
3.9 ab
2.5 be
2.1 c
2.0 c
2.0 c
Little
Angel
5.0 a
3.8 ab
4.0 ab
2.8 be
2.4 c
2.0 c
2.3 c
Lynise
5.0 a
4.6 a
4.7 a
2.4 b
2.0 b
1.9 b
1.6b
0597-3
5.0 a
5.0 a
5.0 a
4.6 ab
4.0 ab
3.6 b
1.9 c
Cultivar
UF474-1
5.0 a
4.8 a
4.4 a
2.7 b
1.0 c
1.0 c
1.0 c
UF576-14
4.4 a
5.0 a
1.8 be
2.7 ba
1.0 cb
1.0 c
1.0 c
Classic
Viscount
5.0 a
4.1 ab
4.1 ab
2.3 c
3.2 be
3.2 be
2.6 be
Petite
4.7 a
4.6 a
4.0 a
4.7 a
2.5 be
3.6 ab
2.0 c
Starlight
5.0 a
5.0 a
5.0 a
4.2 ab
3.1 be
2.2 c
2.1c
Vicki
Lynn
5.0 a
4.6 a
4.1 ab
2.8 be
2.0 c
2.0 c
1.7c
'Quality rating was based on the following scale: 5 = no necrotic damage with excellent leaf color, 4 = no necrosis, but slight leaf discoloration, 3 = 1 to 20%
total leaf necrosis, 2 = more than 21% total leaf necrosis and 1 = plant dead.
^Control temperature ranging from 18-32°C.
xMean within columns followed by the same letter are not significantly different (LSD, P< 0.05).
168 Proc. Fla. State Hort. Soc. 113: 2000.
In two respects, the chilling conditions reported in this re
search were harsher than would be in nature. First, the plants
experienced a sudden exposure to chilling temperatures,
which does occur in nature but is not common. Secondly, the
chilling temperatures were constant throughout the treat
ment. Nevertheless, even under these harsh conditions, sig
nificant cultivar differences were apparent. Using the
identified resistant cultivars may significantly reduce the
chance of chilling injury in production and transportation,
and also decrease heating costs. The resistant cultivars such as
5598, Annette and 0597-3 may be used as breeding material
for improving chilling resistance.
In conclusion, differences in response to chilling temper
atures exist among Spathiphyllum cultivars. The chilling injury
symptoms vary from slow growth, necrotic damage on leaves
to plant death, depending on cultivars. In general, increasing
the severity and duration of the chilling conditions results in
more pronounced injury, of which mature leaves were more
susceptible than younger ones. Invisible injury can occur to
cultivars chilled at 10 or 11°C. Growers should be fully aware
of latent symptoms associated with chilling injury, which can
be and have been misdiagnosed as insufficient nutritional or
cultural practices.
Literature Cited
Beeson, R. C, Jr. 1992. Restricting overhead irrigation to dawn limits growth
in container-grown woody ornamentals. HortScience 27:996-999.
Chen,J., R. J. Henley, R. J. Henny, R. D. Caldwell and C. A. Robinson. 1998.
A simple leaf-assay method for evaluating Aglaonema sensitivity to chilling
temperatures. Proc. Fla. State Hort. Soc. 111:43-46.
Conover, C. A., R. T. Poole and T. A. Nell. 1982. Influence of intensity and
duration of cool white fluorescent lighting and fertilizer on growth and
quality of foliage plants. J. Amer. Soc. Hort. Sci. 107:817-822.
Graham, D and B. D. Patterson. 1982. Response of plants to low, nonfreezing
temperatures: proteins, metabolism, and acclimation. Ann Rev. Plant
Physiol. 33:149-190.
Henley, R. W., R. J. Henny andj. Chen. 1998. Chilling injury on twenty aglaonema
cultivars. Proc. Southern Nurserymen Association Conference 43:117-121.
Huxley, A. 1994. The New Royal Horticultural Society Dictionary of Garden
ing. The Macmillon Press Ltd., London.
Levitt, J. 1980. Responses of Plants to Environmental Stresses. Academic
Press, New York.
Lyons, J. M. 1973. Chilling injury in plants. Ann. Rev. Plant Physiol. 24:445-466.
Lyons, J. M., T. A. Wheaton and H. K. Pratt. 1964. Relationship between the
physical nature of mitochondrial membranes and chilling sensitive in
plants. Plant Physiol. 39:262-268.
Marousky, F. J. 1980. Chilling injury in Dracaena sanderana and Spathiphyllum
'Clevelandii'. HortScience 15:197-198.
Palta, J. P., B. D. Whitaker and L. S. Weiss. 1993. Plasma membrane lipids as
sociated with genetic variability in freezing tolerance and cold acclima
tion of Solarium species. Plant Physiol. 103:793-803.
Poole, R. T., C. A. Conover and Y. Ozeri. 1986. Response of African violets to
fertilizer source and rate. HortScience. 21:454-455.
Raison, J. K and G. R. Orr. 1990. Proposal for a better understanding of the
molecular basis of chilling injury, pp. 145-164. In C. Y. Wang (ed.), Chill
ing Injury of Horticultural Crops. CRC Press. Boca Raton, FL.
Stamps, R. H. and M. R. Evans. 1999. Growth of Dracaena marginataand Spath
iphyllum 'Petite' in sphagnum peat- and coconut coir dust-based growing
media. J. Environ. Hort. 17:49-52.
Taiz, L. and E. Zeiger. 1998. Plant Physiology. Sinauer Associates Inc. Pub
lishers. Sunderland, MA.
Williams, J. P., M. U. Khan, K. Mitchell and G. Johnson. 1988. The effect of
temperatures on the level and biosynthesis of unsaturated fatty acids in di-
acylglycerols of Brassica napus leaves. Plant Physiol. 87:904-910.
Wilson, J. M. 1987. Chilling injury in plants, pp. 272-292. In B. W. W. Grout
and G. J. Morris (eds.), The Effects of Low Temperatures on Biological
Systems. Edward Arnold, London.
Proc. Fla. State Hort. Soc. 113:169-170. 2000.
FLOWERING RESPONSE OF THREE SPATHIPHYLLUM CULTIVARS TO TREATMENT
WITH THREE LEVELS OF GIBBERELLIC ACID
R. J. Henny, J. Chen and T. A. Mellich
University of Florida, IFAS
Mid-Florida Research and Education Center
2725 Binion Road
Apopka, FL 32703
Additional index words. Foliage plant, growth regulator.
Abstract. Spathiphyllum cultivars Petite, Taylor's Green and
Viscount were treated to induce flowering with 0, 125 or 250
ppm gibberellic acid (GA3) applied as a single foliar spray dur
ing August. None of the control plants (0 ppm) had flowered at
fourteen weeks after treatment, whereas 100% flowering was
observed in cultivars Petite and Taylor's Green at both the 125
and 250 ppm gibberellic acid levels. All plants of the cultivar
Viscount also flowered at the 250 ppm rate but only 60% flow
ered at 125 ppm gibberellic acid. Petite produced the highest
Florida Agricultural Experiment Station Journal Series No. N-02009.
total flower count after 14 weeks followed by Taylor's Green
and Viscount which produced the smallest number of flowers
in this experiment.
Spathiphyllum with their dark green foliage and attractive
flowers remain one of the top selling foliage plants produced
in Florida. Spathiphyllum are easy to grow; crops are uniform
and they can be flowered on schedule using gibberellic acid
treatment. The general method for applying GA3 is a single
foliar spray at 250 ppm (Henny, 1981; Henny and Fooshee,
1984). This is an easy and dependable treatment method.
However, there has been no research to investigate if lower
rates could be effective which might reduce chemical costs.
Research has shown that different Spathiphyllum cultivars re
quired different length of time to reach peak blooming and
also displayed differences in total number of flowers pro
duced (Henny et al., 1999). To investigate rate and cultivar
response, 3 Spathiphyllum cultivars were evaluated after be
ing treated at 0, normal and half-normal rates of GA
Proc. Fla. State Hort. Soc. 113: 2000. 169
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