Journal of Experimental Botany, Vol 49, 761-774, Copyright © 1998 by Oxford University Press
J Croker, W Witte and R Auge
The objective of this study were to (1) characterize stomatal response of
six deciduous tree species to non-hydraulic, root-sourced signals of soil
drying, and (2) test whether species sensitivity to non-hydraulic
signalling is allied with their drought avoidance and tolerance profiles.
Saplings were grown with roots divided between two pots. Three treatments
were compared: one half of the root system watered and half droughted (WD),
one half of the root system watered and half severed (WS), both halves
watered (WW). Drying about half of the root system caused non-hydraulic
declines in stomatal conductance (gs) in all species,
with gs of WD plants reduced to from 40% to 60% of WS
controls. Declines in stomatal conductance were closely related to
declining soil matric potential (
ARTICLES
Stomatal sensitivity of six temperate, deciduous tree species to non-hydraulic root-to-shoot signalling of partial soil drying
Tennessee Agricultural Experiment Station, OHLD, University of Tennessee, PO Box 1071, Knoxville, TN 37901-1071, USACorresponding author; e-mail: auge@utk.edu
m) between -0.01 and -0.10 MPa.
Soil m required to cause declines in gs of
WD plants to 80% of WS controls varied from a high of -0.013 to a low of
-0.044 MPa. Stomatal inhibition varied somewhat with leaf age in half of
the species. Leaf osmotic potentials during soil drying were mostly similar
among treatments. Although stomatal sensitivity to the non-hydraulic,
root-sourced signal (characterized as decline in gs
per unit decline in soil ) was not closely correlated with
previously identified lethal leaf water potentials or capacity for osmotic
adjustment, species having the highest stomatal sensitivity also had the
least hydration tolerance. This suggests that stomatal sensitivity to
non-hydraulic root signals may be mechanistically linked to a limited
extent with other characteristics defining relative species drought
tolerance.Keywords: Non-hydraulic signalling, osmotic
potential, stomatal conductance, temperate deciduous trees, water
relations.
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