Selection of Eucalyptus urophylla cell lineages for tolerance to hydric and thermal stress

Abstract

The present study was aimed at the evaluation of the possible relationship between high temperature sand increased tolerance to water deficiency of Eucalyptus urophylla cell lineages on their physiological and biochemical aspects. For this purpose, calluses cultures derived from hypocotyls Eucalyptus urophylla were maintained in tissue culture in an N7 culture medium with 5 mg L^-1 Picloram and used to conduct tests. The calluses were treated at different temperatures (25, 30, 35, 40 and 45°C) for 2 h in BOD and then subjected to a selection pressure in N7 medium supplemented with 20% polyethylene glycol (PEG 6000) for 20 days under constant light exposure (42 μmol m^-2 s^-1 PAR) and temperature (26±2°C) conditions with a 12 h photoperiod. For evaluate the experiment, proline, total soluble proteins, glucose, polyose and glucuronic acid contents were determined as well as the relative growth rate by measuring dry weight and fresh weight. The results indicated that previous treatment with higher temperatures may increase tolerance to drought stress. Therefore tolerant cell lines to stress conditions can be selected using this methodology.