STUDY OF HIGH TEMPERATURE EFFECT ON CHESTNUT SEEDLINGS GROWTH

Abstract

'Judia' variety progenies were put to grow under 25°C and 35°C in order to evaluate their adaptative capacity. Therefore, two groups of chestnut seedlings grew at control temperature (25°C) during 90 days. After this period group T3 5 was placed at 35°C for more 60 days, while the group T 25 was maintained at 25°C. Temperature curves (20-36°C) to evaluate photosynthetic rate were made at two different periods, 90 and 150 days. In the 1 st period no significant differences were observed between groups, being maximal rate measured at 32.5°C (T 100 ). Concerning the 2 nd period, group T 25 showed that T 100 decreased to 30°C while in group T 35 , T 100 no changes were observed. Nevertheless, in group T 35 a significant reduction in the maximal photosynthetic rate was observed (33%) as well as a significant increase of the Chl a/b ratio (3.15 to 3.37). Concerning the membrane potential (2 nd period), in group T 25 , a maximal value was obtained between 19-20°C range while in the other group the temperature increased 2°C. We also evaluate the activities of superoxide dismutase (SOD) and catalase (CAT). SOD activity was significantly stimulated at 35°C (14%), whereas CAT did not show any significant alteration between groups. In relation to the lipid content we observed that plants grown at the higher temperature (35°C) show an increased percentage of saturated fatty acids.