WHERE DOES STEM CAPACITANCE WATER COME FROM? KASIA ZIEMIŃS KA 1 , EMILY ROSA 2 AND SEAN GLEA SON 3 , N. MICHELE HOLBROOK 4 1 [email protected], Arnold Arboretum of Harvard University, Boston, MA; 2 California State University, Sonoma, CA; 3 USDA-ARS, Water Management Unit, Fort Collins, CO; 4 Dept. of Organismal and Evolutionary Biology, Harvard University, Cambridge, MA BACKGROUND AND QUESTIONS Stored water can contribute significantly to trees’ daily transpiration stream 1-4 . But where does this water come from? It is often sug- gested that parenchyma tissue (Fig. 1) contrib- utes this water, yet there has been no convinc- ing evidence supporting this claim. Parenchy- ma proportion varies greatly across species (from ~5-90%) 5 , so could this variation drive different capacitance strategies? METHODS 30 tree species from 26 families (3 reps/species) temperate angiosperms Arnold Arboretum of Harvard University twig wood predawn (pd) and midday (md) stem water potential measured using bagged leaf method (Aug 2017) capacitance pd-md : water released between predawn and midday per unit volume of wood (kg m -3 ) / stem water potential change between predawn and midday (MPa) wood anatomical traits: all tissues lumen and wall fractions, vessel diameter, proportion of vessel circumference in contact with other tissues RESULTS Capacitance pd-md was not related to parenchyma lumen fraction (Fig. 2) or to any other tissue fraction except for, weakly, to vessel lumen fraction (r 2 =0.14*). Instead, wood density and lumen volumetric water content (proportion of wood volume that is occupied by water in lumen) were strongest predictors of capac- itance (r adj 2 =0.44, P<0.0001): CAPACITANCE PD-MD ~ + LUMEN VOLUMETRIC WATER CONTENT PD - WOOD DENSITY Vessel-tissue contact fractions (vessel-ray, vessel-axial parenchyma, vessel-fi- bre) each explained an additional ~10% of variation in capacitance pd-md . Average relative water content was 0.65±0.13 and average volumetric water contet change between predawn and midday was 0.04±0.02 (Fig. 3). CONCLUSIONS Tissue fractions don’t seem to limit capacitance pd-md across the studied species. Rather, capacitance pd-md may depend on total stored water, bulk wood proper- ties resulting from wood density (e.g. elastic shrinkage) and tissue connectivity. Relative water content values indicate parts of wood are devoid of water. Small volume of water released between predawn and midday imply that water could be released from any tissue and more sophisticated techniques need to be used to observe this phenomenon. SIGNIFICANCE This study challenges the conviction that more parenchyma provides higher wood capacitance. The functional meaning of vast parenchyma fraction varia- tion remains unclear and intriguing. THIS WORK IS AVAILABLE AS A PREPRINT ON BIORXIV LINK ACKNOWLEDGEMENTS We would like to thank the Arnold Arboretum staff for wonderful support and discussions. This study was funded by Postdoctoral Putnam Fellowship awarded to KZ and DaRin Butz undergraduate scholarship awarded to ER. BIBLIOGRAPHY Carrasco et al. Tree Phys 2015, 2 Goldstein et al. PCE 1998, 3 Scholz et al PCE 2007, 4 Meinzer et al. Tree Phys 2004, 5 Morris et al. New Phyt 2016 FIGURE 3. Volumetric and relative water content. ‘Volumetric water content’ is the volume of water in a fresh wood sample per volume of that entire sample (water+wood). ‘Relative water content’ is the mass of water in a fresh sample per mass of water in a saturated sample. Caution: some of the water may be within cell walls. three letter code stands for first three letters of the genus in Latin. FIGURE 2. Relationship between capacitance and parenchyma lumen fraction (ray+axial). Capacitance is defined as water (kg) released from wood (m 3 ) between predawn and midday per stem water potential change (MPa). This result suggests that high parenchyma fraction may not be required for high capacitance. However, this does not imply that parenchyma doesn’t contribute to capacitance. three letter code stands for first three letters of the genus in Latin (have a guess or ask me about them). diffuse-porous, semi/ring-porous r 2 =0.13, P<0.1 VESSEL transports water AXIAL PARENCHYMA stores and transports nutrients RAY PARENCHYMA stores and transports nutrients FIBRE gives mechanical support FIGURE 1. Cross-section, twig wood, Fagus grandifolia PARENCHYMA LUMEN FRACTION CAPA CITANCE pd-md kg m -3 MPa -1 ace aes alb bet car cat cer cla cor dio euc fag fra gle liq lir mac cat VOLUMETRIC WATER CONTENT RELATIVE WATER CONTENT 1.0 0.8 0.9 0.7 0.6 0.4 0.3 0.2 0.1 0.5 0.0 0.0 0.2 0.1 0.3 0.4 0.6 0.7 0.8 0.9 0.5 1.0 fra sas pic dio mac car cla lir gle tet ace mag zel mor til que bet sty sty fag aes euc oxy liq alb cer pau cor phe midday predawn mag mor oxy phe pic que sas ste sty tet til zel ‘gle’ ‘gle’ 0.1 0.15 0.2 0.25 0.3 0 20 40 60 80 100 500 pau
WHERE DOES STEM CAPACITANCE WATER COME FROM? · WHERE DOES STEM CAPACITANCE WATER COME FROM? KASIA ZIEMIŃSKA1, EMILY ROSA2 AND SEAN GLEASON3, N. MICHELE HOLBROOK4 [email protected],
Jun 27, 2020
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
WHERE DOES STEM CAPACITANCE WATER COME FROM?KASIA ZIEMIŃSKA1, EMILY ROSA2 AND SEAN GLEASON3, N. MICHELE [email protected], Arnold Arboretum of Harvard University, Boston, MA; 2California State University, Sonoma, CA; 3USDA-ARS, Water Management Unit, Fort Collins, CO; 4 Dept. of Organismal and Evolutionary Biology, Harvard University, Cambridge, MA
BACKGROUND AND QUESTIONSStored water can contribute significantly to trees’ daily transpiration stream1-4. But where does this water come from? It is often sug-gested that parenchyma tissue (Fig. 1) contrib-utes this water, yet there has been no convinc-ing evidence supporting this claim. Parenchy-ma proportion varies greatly across species (from ~5-90%)5, so could this variation drive different capacitance strategies?
METHODS 30 tree species from 26 families (3 reps/species) temperate angiosperms Arnold Arboretum of Harvard University twig wood predawn (pd) and midday (md) stem water potential measured using bagged leaf method (Aug 2017) capacitancepd-md: water released between predawn and midday per unit volume of wood (kg m-3) / stem water potential change between predawn and midday (MPa) wood anatomical traits: all tissues lumen and wall fractions, vessel diameter, proportion of vessel circumference in contact with other tissues
RESULTSCapacitancepd-md was not related to parenchyma lumen fraction (Fig. 2) or to any other tissue fraction except for, weakly, to vessel lumen fraction (r2=0.14*). Instead, wood density and lumen volumetric water content (proportion of wood volume that is occupied by water in lumen) were strongest predictors of capac-itance (radj
2=0.44, P<0.0001):CAPACITANCEPD-MD ~ + LUMEN VOLUMETRIC WATER CONTENTPD - WOOD DENSITY
Vessel-tissue contact fractions (vessel-ray, vessel-axial parenchyma, vessel-fi-bre) each explained an additional ~10% of variation in capacitancepd-md. Average relative water content was 0.65±0.13 and average volumetric water contet change between predawn and midday was 0.04±0.02 (Fig. 3).CONCLUSIONSTissue fractions don’t seem to limit capacitancepd-md across the studied species.Rather, capacitancepd-md may depend on total stored water, bulk wood proper-ties resulting from wood density (e.g. elastic shrinkage) and tissue connectivity.Relative water content values indicate parts of wood are devoid of water.Small volume of water released between predawn and midday imply that water could be released from any tissue and more sophisticated techniques need to be used to observe this phenomenon.SIGNIFICANCEThis study challenges the conviction that more parenchyma provides higher wood capacitance. The functional meaning of vast parenchyma fraction varia-tion remains unclear and intriguing.THIS WORK IS AVAILABLE AS A PREPRINT ON BIORXIV LINKACKNOWLEDGEMENTSWe would like to thank the Arnold Arboretum staff for wonderful support and discussions. This study was funded by Postdoctoral Putnam Fellowship awarded to KZ and DaRin Butz undergraduate scholarship awarded to ER.BIBLIOGRAPHY Carrasco et al. Tree Phys 2015, 2Goldstein et al. PCE 1998, 3Scholz et al PCE 2007, 4Meinzer et al. Tree Phys 2004, 5Morris et al. New Phyt 2016
FIGURE 3. Volumetric and relative water content. ‘Volumetric water content’ is the volume of water in a fresh wood sample per volume of that entire sample (water+wood). ‘Relative water content’ is the mass of water in a fresh sample per mass of water in a saturated sample. Caution: some of the water may be within cell walls. three letter code stands for first three letters of the genus in Latin.
FIGURE 2. Relationship between capacitance and parenchyma lumen fraction (ray+axial). Capacitance is defined as water (kg) released from wood (m3) between predawn and midday per stem water potential change (MPa). This result suggests that high parenchyma fraction may not be required for high capacitance. However, this does not imply that parenchyma doesn’t contribute to capacitance. three letter code stands for first three letters of the genus in Latin (have a guess or ask me about them). diffuse-porous, semi/ring-porous
r2=0.13, P<0.1
VESSEL transports water
AXIAL PARENCHYMA stores and transports nutrients
RAY PARENCHYMAstores and transports nutrients
FIBREgives mechanical support
FIGURE 1. Cross-section, twigwood, Fagus grandifolia
PARENCHYM A LUMEN FR ACT ION
CAP
ACIT
ANCE
pd-m
d
kg m
-3 M
Pa-1
ace
aes
alb
bet
car
catcer
cla
cor
dio
euc
fag
fra
gle
liqlir
mac
cat
VOLU
MET
RIC
WAT
ER C
ONTE
NT
RELA
TIVE
WAT
ER C
ONTE
NT
1.0
0.8
0.9
0.7
0.6
0.4
0.3
0.2
0.1
0.5
0.0
0.0
0.2
0.1
0.3
0.4
0.6
0.7
0.8
0.9
0.5
1.0
fra sas pic dio mac car cla lir gle tet ace mag zel mor til que bet sty sty fag aes euc oxy liq alb cer paucorphe
middaypredawn
mag
mor
oxy
phe
pic
quesas
ste
sty
tet
til
zel
‘gle’ ‘gle’
0.1 0.15 0.2 0.25 0.3
020
4060
8010
050
0 pau
Related Documents
