RT Journal Article
SR Electronic
T1 pH-Regulated Leaf Cell Expansion in Droughted Plants Is Abscisic Acid Dependent
JF Plant Physiology
JO Plant Physiol.
FD American Society of Plant Biologists
SP 1507
OP 1515
DO 10.1104/pp.118.4.1507
VO 118
IS 4
A1 Bacon, Mark A.
A1 Wilkinson, Sally
A1 Davies, William J.
YR 1998
UL http://www.plantphysiol.org/content/118/4/1507.abstract
AB Elongation rates of barley (Hordeum vulgare L. cv Hanna) leaves decreased with decreasing soil water content, whereas the pH of xylem sap increased from 5.9 to 6.9 over 6 d as the soil dried. The reduction in leaf-elongation rate (LER) was correlated with the increase in sap pH. Artificial sap buffered to different pH values was fed via the subcrown internode to derooted seedlings. Although leaves elongated at in planta rates when fed artificial sap at a well-watered pH of 6.0, LER declined with increasing sap pH. This effect persisted in the light and in the dark. pH had no effect on the relative water content or the bulk abscisic acid (ABA) concentration of the growing zone of these leaves. LERs of the ABA-deficient mutant Az34 were uniformly high over the pH range tested, whereas those of its isogenic wild-type cultivar Steptoe were reduced as the artificial sap pH was increased from 6.0 to 7.0. However, supplying a well-watered concentration of ABA (3 × 10−8 m) in the artificial xylem sap restored the pH response of the Az34 mutant. The results suggest that increased xylem sap pH acts as a drought signal to reduce LER via an ABA-dependent mechanism. ASartificial xylem sapLERleaf-elongation rateRIAradioimmunoassay