Acclimation of Soybean Plants to Water Deficit III. Changes in leaf growth as regulated by “leaf extensibility” and pressure potential under various soil water regimes

Abstract

In our previous paper6), it was shown that the increasing rate of the total leaf area of a single soybean plant was strongly depressed immediately after reducing soil water content to a low level, and that it recovered to a fairly large extent thereafter even though the soil water content was maintained at the same low level. This result suggests that a kind of acclimation occurs during leaf growth of soybean plants when water stress is prolonged. The objectives of this paper are to confirm the phenomenon, and further, to find out the physiological basis for it at the level of a single leaf. Since the turgor pressure of the leaf tissue cells is undoubtedly the motive force of leaf expansion1,11, it is thought to be one of the internal factors regulating the rate of leaf expansion. In addition to this, the degree of extension of the leaf tissues by a given stress, that is, their physical extensibility is also thought to be another factor regulating the leaf expansion rate4,8). Thus, we investigated the physiological basis of acclimation in leaf growth to soil water regimes from the view points of (1) pressure potential of leaf tissues and (2) “leaf extensibility” measured by the procedure described later. © 1987, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.