PLANT PHYSIOLOGY , Vol 109, Issue 3 1017-1024, Copyright © 1995 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
A Negative Hydraulic Message from Oxygen-Deficient Roots of Tomato Plants? (Influence of Soil Flooding on Leaf Water Potential, Leaf Expansion, and Synchrony between Stomatal Conductance and Root Hydraulic Conductivity)
M. A. Else, W. J. Davies, M. Malone and M. B. Jackson
IACR-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol BS18 9AF, United Kingdom (M.A.E., M.B.J.)
Four to 10 h of soil flooding delayed and suppressed the normal daily
increase in root hydraulic conductance (Lp) in tomato (Lycopersicon
esculentum Mill. cv Ailsa Craig) plants. The resulting short-term loss of
synchrony between Lp and stomatal conductance decreased leaf water
potential ([psi]L) relative to well-drained plants within 2 h. A decrease
in [psi]L persisted for 8 h and was mirrored by decreased leaf thickness
measured using linear displacement transducers. After 10 h of flooding,
further closing of stomata and re-convergence of Lp in flooded and
well-drained roots returned [psi]L to control values. In the second
photoperiod, Lp in flooded plants exceeded that in well-drained plants in
association with much increased Lp and decreased stomatal conductance.
Pneumatic balancing pressure applied to roots of intact flooded plants to
prevent temporary loss of [psi]L in the 1st d did not modify the patterns
of stomatal closure or leaf expansion. Thus, the magnitude of the early
negative hydraulic message was neither sufficient nor necessary to promote
stomatal closure and inhibit leaf growth in flooded tomato plants. Chemical
messages are presumed to be responsible for these early responses to soil
flooding.
