Alterações fisiológicas e bioquímicas de duas variedades de cana-de-açúcar sob estresse hídrico

Abstract

This study aimed to characterize the physiological responses to drought of two sugarcane (Saccharum spp.) varieties in order to contribute information to study the physiological processes involved in plant adaptation to drought. To this end, an experiment was installed in a completely randomized design in a greenhouse at the Laboratory of Plant Physiology of the Center for Agrarian Sciences, Federal University of Alagoas, located in Rio Largo - AL (9° 28 S, 35° 49 W, with 127 m of altitude), and where the varieties RB855536 and RB867515 with contrasting responses to drought, were subjected to two, four, six and eight days of water stress and rehydration. The physiological and biochemical variables were analyzed, leaf water potential (w), solute potential (s), chlorophyll fluorescence (Fv/Fm and ФPSII), soluble sugars (glucose, fructose, sucrose) and starch and antioxidant enzymes, catalase (CAT), superoxide dismutase (SOD) and ascorbate peroxidase (APX). Water stress resulted in significant reduction in the w and s in two varieties studied, which did not support a drought of more than six days. After rehydration, the varieties studied, showed the ability to restore in the w and s. The RB867515 had greater reductions in the w and s in relation to RB855536. Both varieties studied presented chronic and dynamic photoinhibition gradually with the increase in time of drought stress and a strong reduction in the quantum potential efficiency (Fv/Fm) and effective (ΦPSII). The variety RB867515 showed higher capacity of recovery of the ΦPSII and rapair the effects of photoinhibition. The drought caused the decrease in the levels of sucrose and starch in two varieties, with greater reduction of recovery sucrose and starch compared to control, presented by RB867515. Increases in the levels of glucose and fructose were also observed in both varieties under water restriction. Changes in levels of sugars, indicating that rising levels of glucose and fructose occurred through the degradation of sucrose and starch, likely to hold the osmotic adjustment. The variety RB867515 showed higher activity of CAT and APX, in relation to RB855536, and SOD activity increased with increasing time of drought. In this work, the variety RB867515 showed greater efficiency in the activation of mechanisms of tolerance to drought stress.