Changes in Anatomical Structure and Levels of Endogenous Phytohormones during Leaf Rolling in Ctenanthe setosa under Drought Stress

Abstract

Leaf rolling occurs as a response to water deficit and its level increases as the drought period is progressing in plants. Changes in anatomical structure and levels of endogenous phytohormones were investigated under drought stress during leaf rolling in Ctenanthe setosa. Leaf water potential (\Psi_{leaf}), some anatomical parameters, and the levels of phytohormones were determined at different visual levels of leaf rolling from 1 to 4. \Psi_{leaf}, thickness of mesophyll and lamina, and width/length ratio of hypodermis cells of leaves decreased while leaf rolling level increased. Diameters of xylem vessels and median vein, and length of upper and lower stomatal guard cells also decreased during leaf rolling. The amount of indole-3-acetic acid (IAA) increased up to the 3^{rd} level of leaf rolling but it declined to the value of the 1^{st} level at the 4^{th} level of rolling. The gibberellic acid (GA_{3}) level changed irregularly during leaf rolling. Trans-zeatin and abscisic acid (ABA) amounts also increased during the rolling period. The analysis showed that changes in the levels of these phytohormones may affect the anatomical structure of the leaf during the rolling period under drought stress.