The Evolution of Wood Anatomical Diversity and its Significance · 2016-11-21 · •Conclusion: adaptive evolution is driver of wood anatomical diversification •Research questions
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The Evolution of Wood Anatomical
Diversity and its Significance
Pieter Baas
Contents
• A bit of history
• Wood in the living tree
• Wood diversity
• Integration of phylogenetic and
ecological approaches to the
study of xylem evolution
• Wood anatomy and climate change –
proxies for mean annual
temperature in wood structure
• Conclusions
Quercus wood as seen by Grew, Malpighi and Leeuwenhoek - three
functional tree biologists!
Ludwig Radlkofer
(1829—1927)
1883 in Munich: The
next hundred years
belong to the
anatomical method
Sapindaceae taxonomy
& morphology (including
wood anatomy)
Pinus longaeva -bristlecone pine
Hydraulic architectural types
Softwood Diffuse-porous hardwood Ring-porous hardwood
Tropical diffuse-porous tree
(Shorea) and climber (Serjania)
Temperate diffuse-porous (Aesculus) and
ring-porous (Quercus) trees
Dicot
Woods
I.W. Bailey (1884—
1967)
• Xylem evolution
• Fossil woods
• Wood properties
(preservatives)
• Tree pathology
• Wood Identification
• Cambium
• Cell wall structure
• Vestured pits
1918
Bailey & Tupper
Size variation in
tracheary cells = Major
trends in xylem
evolution
“Inspirational”
Pieter Baas and others
or:
“Outdated and
unnecessary” ??
Marc Olson –Botan.
Rev. 2012 (and others) Swamy,
1954
Wood evolution
from vesselless
gymnosperms to
vessel-bearing
angiosperms
Conductivity Strength
Division of labour
Simple and
scalariform
perforations
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Cretaceous Eocene Miocene RecentPaleo Oligo Pli
o
What Was The Incidence of Perforation
Plate Types in Geologic Past?
Simple
Scalariform
Cretaceous - Recent
P. Gasson
Photo by S. Noshiro, Perforation Plate in Davidia
Scalariform perforation
& Vestured pits
Do
Vestures
reduce
cavitation
risk?
Zweypfenning
1978
Scalariform
perforations
plotted on the
Soltis tree are
much more
common in
basal clades
vestured
pits (**)
on Soltis tree
0
5
10
15
20
25
30
35
40
45
50
Deserts Tropical
lowlands
seasonal
Tropical
lowlands
everwet
Subtropical-
warm
temperate
Tropical
mountains
Cool
temperate
Boreal-arctic
Mean % vestured pits Mean % exclusively scalariform perforations
Ecological trends in (vestured pits and)
scalariform perforations (purple)
Jansen et al.2004, PNAS
< 5 , 5 - 20, 20 - 40, > 40-- Vessels per sq. mm
North America, Temperate Asia, Europe similar to one another Tropical America, Africa, SE Asia similar to one another
< 50 µm , 50 - 100 µm, 100 - 200 µm, > 200 µm --Mean Vessel Diameter
Regions with high proportions of narrow vessels have low proportions of ‘few vessels per sq. mm’
Present-Day Woods
Wheeler, Baas, Rodgers 2007 IAWA J
Trees / Small Trees / Shrubs
Trees wider diameters than
shrubs.
Shrubs have a higher % of
narrowest vessels
Wide vessels restricted to
trees (almost)
Vessel Mean Tangential Diameter in
Trees n = 4840
Small Trees n = 663
Shrubs n = 630
< 50 µm 50-100 µm 100–200 µm > 200 µm
Triangle of wood functions and trade-offs
NARROW VESSELS
Work of
F. Ewers
J. Sperry
U. Hacke
S. Davis
Summary of functional ecological trends
1. In tropical - temperate - boreal - arctic gradients:
Scalariform perforations become more common
Element length decreases
Vessel diameter decreases
Vestured pits become rarer
2. In mesic - xeric gradients:
Scalariform perforations become very rare
Element length decreases
Vessel diameter decreases
Vestured pits become more common
Confounding for temperature and moisture proxies!
Also clade dependent (phylogeny)
Additional Wood Anatomical Proxies for Warmer Climates
• Storied structure +
• Ring porosity –
• Parenchyma rare or absent –
• Paratracheal parenchyma +
• Marginal parenchyma –
• Septate fibres +
• Homocellular rays –
Wiemann et al. 1999; Wheeler et al. 1993, 2007
Scale matters!
• Within wild Olea europaea in Europe vessel density is positively related with MAT (Téral & Mengüal 1999)
• Within world flora vessel density negatively related with MAT (Wheeler et al. 2007)
Interim Conclusion No. I
• Wood anatomy contains very strong ecologically adaptive signals (temperature, water, etc.)
• Some of these signals (perforation type, vestured/nonvestured pits) also contain very strong phylogenetic signals
• Conclusion: adaptive evolution is driver of wood anatomical diversification
• Research questions have to take into account spatial, temporal, and taxonomic scales
Harissonia (2x)
* Cneorum tricoccon
Dictyoloma
Wood anatomy of
Spathelioideae
very similar to that
of other Rutaceae
H.J. Braun (1963, 1970)- Functional Type Rhamnus
Rationale for Links between
Climate and Wood Evolution
• Photosynthesis ~ Gas Exchange ~ Stomatal opening ~
Transpiration
• High CO2 ~ Low stomatal frequency ~ Lower demands on
conductivity
• Climate ~ water vapour deficit ~ drought stress ~ cavitation
• Conductivity ~ 4th Power Conduit Radius ~ vessel density
• Resistance to flow: perforation plates & pit membranes
• Cavitation resistance (drought stress) : vessel diameter,
vestured pits, pit membrane ultrastructure?
• Cavitation resistance (freeze-thaw cycle): vessel diameter,
scalariform perforations
• Forest Canopy transpiration regulates climate
– Jarmila Pittermann 2010
Wood Anatomy and Climate Change 1: Tree rings
Wood Anatomy and Climate Change 2: Vantage Fossil Wood
example
• Rich Mid-Miocene assemblage (Wheeler & Dillhoff, 2009, IAWA Journal Supplement 7)
• Mean Annual Temperature reconstruction based on qualitative wood anatomical proxies
X
Ginkgo Petrified Forest State Park, WA, USA = Vantage Woods
Vantage Woods 15.5 my,mid-Miocene
MAT = 24.78 + 36.57 (% storied rays) - 15.61 (% marginal parenchyma) - 16.41 (% axial parenchyma rare to absent)
Wiemann, M.C., E.A. Wheeler, S.R. Manchester, & K.M. Portier. 1998. Dicotyledonous wood anatomical characters as predictors of climate. Palaeogeography, Palaeoclimatology, Palaeoecology 139: 83--100. Wiemann, M.C., S.R. Manchester, & E.A. Wheeler. 1999. Paleotemperature estimation from dicotyledonous wood characters. Palaios 14: 460--474.
Estimating MAT oC using wood
physiognomy
If treat Vantage Fraxinus as a tendency to storied rays, MAT estimate of 12.8 oC,
If storied rays absent, the MAT estimate is 12.1 oC
Recent Temperate Deciduous Broad-leaved Forests of China have MAT of 10 -- 14.6
oC
Recent Mixed Mesophytic Forests of China have MAT of 11.4--16.4
oC
33 Dicot Wood Types From Main Vantage Locality
Wang, Chi-Wu. 1961. The Forests of China. Maria Moors Cabot Foundation
Publication No. 5
Northern Hemisphere
Wolfe, J.A. 1978
Amer. Sci. 66; 694-703
60 50 40 30 20 10 0
60
AGE Million years before present (Ma)
Y = Estimates of To:
% leaves with entire
margins, O Isotopes
% E
ntire
-Marg
ined L
eaves
Infe
rred M
AT.
o C
0
30o
Past climate change inferred from leaf
margins and Oxygen isotopes
Vantage woods
MAT
Nutbeds
woods
MAT
Experimental Studies
• Increased temperature results in:
increased wood density
lower vessel diameter
lower flow resistance (lower sap viscosity)
• Increased CO2 results in:
increased growth
decreased wood density
lower vessel diameter
Caution: limitations of short term experiments
Interim Conclusion 2
• Wood anatomy contains wealth of climatic signals from past and present
• Wood anatomical profiles of species assemblages are underutilised as environmental proxies
• Is this the full story??
Air-seeding pressure (MPa)
Perc
en
tag
e l
oss o
f co
nd
ucti
vit
y
Lens et al. 2011. New Phytologist 190: 709-723
Cavitation s
ensititve
Cavitation r
esis
tant
Vulnerability curves vs. P50
Cavitation resistance
R² = 0,891
0
50
100
150
200
250
300
350
400
-3,5 -3 -2,5 -2 -1,5 -1 -0,5 0
PM thickness-P50
A. platanoides P50: -2.29MPa
1000 nm 1000 nm 1000 nm
A. grandidentatum P50: -3.19MPa A. saccharinum P50: -1.26MPa
Lens et al. 2011. New Phytologist 190: 709-723
PM PM
PM
P = 0.004
Acer
R² = 0,9293
0
100
200
300
400
500
600
700
800
-4 -3,5 -3 -2,5 -2 -1,5 -1 -0,5 0
pit chamber depth-P50
P = 0.001
V
V
V
V
V
V
Lens et al. 2011.
New Phytologist
190: 709-723
Tight correlation between ultrastructural IV pit characters and Mean Cav. Press. in Acer
pit m
em
bra
ne t
hic
kness
pit c
ham
ber
de
pth
(t/b
) square
wo
od
de
nsity
wid
th o
f w
all
thic
kenin
gs in inner
vessel w
alll
dia
me
ter
of
pit m
em
bra
ne p
ore
s
vessel le
ngth
vessel gro
upin
g index
hydra
ulic
cconductivity p
er
xyle
m a
rea
num
ber
of
thic
ken
ing
s o
n inn
er
vessel w
all
pit a
pert
ure
shape
conta
ct
fraction
pit a
pert
ure
fra
ction
vessel ele
ment
length
mesom
orp
hy index
pit fra
ction
log-t
ranfo
rmed v
essel le
ngth
avera
ge p
it n
um
ber
per
vessel
mean v
essel dia
mete
r
vuln
era
bili
ty index
vessel density
Ap: pit a
rea p
er
vessel
2x v
essel w
all
thic
kness
pit m
em
bra
ne d
iam
ete
r
fiber
length
pit correlations
nonpit
correlations
mem
bra
ne p
oro
sity
Conclusions no. 3
• Major breakthroughs in last 10 years about understanding roles of pit membrane ultrastructure and thickness (Choat, Sano, Jansen, Lens, a.o.).
• Experimental evidence for role of other attributes: perforation type, helical wall thickenings, vessel grouping – what is more to come?
• Vessel diameter-vessel density trade-offs exist, but only explain a small fraction of efficiency-safety trade-offs!
• Vessel diameter could be fully dependent on tree size (tapering conduit model of Anfodillo)?
Special IAWA Journal Issue 2013
• Proceedings of COST-Action STREeSS and IAWA/IUFRO meeting in Naples, April 2013
• Twelve papers: reviews, new methods to observe functional traits, and integrative physiological and anatomical studies
• Guest editors Veronica de Micco, Giovanna Battipaglia and Frederic Lens
Thank You and thanks to:
• Frederic Lens
• Peter Gasson
• Elisabeth Wheeler
• Steven Jansen
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