Effect of Water Deficit on Self-thinning Line in Spring Wheat (Triticum aestivum L.) Populations A Confocal Technique Applicable to Studies of Cellular pH-related Signaling in Plants Regulation of Water Deficit-Induced Abscisic Acid Accumulation by Apoplastic Ascorbic Acid in Maize Seedlings THE DYNAMICS OF SIZE INEQUALITY IN SPRING WHEAT POPULATIONS UNDER SEMIARID CONDITIONS AND ITS PHYSIOECOLOGICAL BASIS