Efeitos da rustificação em mudas de eucalipto na tolerância ao déficit hídrico

Abstract

Hardening is important due it induces modifications in different tissues and consequently to the confrontation of water deficit. During this process plant modifies responses at molecular and physiological levels. The objective of this work was to analyze the physiological and molecular responses of eucalipt urograndis submitted to hardening and compare the responses of hardened and non-hardened seedlings subjected to water stress. The hardening was carried out in the period of 31 days. Physiological and molecular parameters were analyzed, during hardening and water stress experiment which as carried out after seedling hardening and lasted 14 days. During hardening it was observed that leaf water potential (Ψw) decreased with mean between the minimum and maximum potentials ranging from -0.23 MPa on the first day to -0.48 MPa in the latter. It was observed significant differences (p <0.001) among the treatments for total chlorophyll where non-hardened seedlings showed higher chlorophyll content. Photosynthesis (Ft), internal carbon (Ci) and stomatal conductance (Gs) showed significant differences between treatments (p <0.05). Increase in the activity of the enzimes SOD, CAT e MDHAR was observed indicating an increase in the leaves of reactive oxigen species (ROS). In the anatomical analyzes of the radial parenchyma external to the xylem, it is possible to verify an increase in the number of cells stained with lugol in seedlings during hardening. Hardened seedlings and non-hardened when submitted to water deficit showed a different response to photosynthesis and stomatal conductance. Non-hardened seedlings presented a higher percentage of seedlings showing wilting symptoms at 14 days (100%) of which 69% presented apparent wilting and 31% of permanent wilting. Hardened seedlings presented 20% without wilting, 52% of apparent wilting and 28% of permanent wilting. It is concluded that hardening changes the physiological and molecular responses of the seedlings and these modifications are associated with the positive response of the acclimated seedlings to stress conditions imposed by the water deficit.