Revista Ciência Agronômica (Dec 2012)
Alterações fisiológicas e bioquímicas em sementes de arroz submetidas ao estresse térmico Physiological and biochemistry changes in seeds of rice subjected to heat stress
Abstract
O objetivo deste trabalho foi analisar o efeito de diferentes temperaturas na atividade respiratória, enzimática e em processos relacionados à qualidade fisiológica de sementes de arroz, bem como utilizar a relação entre esses parâmetros como forma de caracterizar o início do processo de deterioração de sementes. As sementes foram expostas por 24 h às temperaturas de 15; 25; 30 e 35 ºC, e conduzidas aos testes de germinação, primeira contagem de germinação, índice de velocidade de germinação, comprimento e massa seca da parte aérea e raiz, condutividade elétrica, atividade respiratória e enzimática. O delineamento experimental foi inteiramente casualizado, com quatro repetições, sendo as médias comparadas pelo teste de Tukey (p 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 ºC 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 ºC can depreciate the quality of these seeds.
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