Alterações fisiológicas e bioquímicas em sementes de arroz submetidas ao estresse térmico

Abstract

The purpose of this research was to analyze the effect of different temperatures on the respiratory activity, enzymatic and in process related to the physiological quality of rice seeds, and use the relationship between these parameters to characterize the beginning of the deterioration process of seeds. The seeds were exposed during 24 h and conducted tests for germination, first count germination, index the germination speed, length and dry weight of shoot and roots, electrical conductivity, respiratory activity and activity of the enzymes. The experiment was completely randomized with four replicates and the averages compared by Tukey test (p ≤ 0.05) with subsequent analysis of regression. Rice seeds showed that the germination and vigor were reduced above 25 °C temperatures. Respiratory activity increased with increasing temperature, the same occurred with study enzymes activity in at five days after sowing (ranging from 14.55 at 59.86 μmol of NAD+ g -1 MF min -1 for at malate dehydrogenase and 0.25 at 0.57 μmol of at NADPH g -1 MF min -1 for glucose-6-phosphate dehydrogenase). Therefore, it can be concluded that the evaluated biochemical tests can be used to identify the beginning of the deteriorating process of rice seeds and that temperatures above 25 °C can depreciate the quality of these seeds.