Desempenho fisiológico de sementes de arroz (Oryza sativa L.) tratadas com 24-epibrassinolídeo

Abstract

The objective of the research was evaluate the importance 24-epibrassinolide in physiological performance of rice seeds, for this two experiments were conducted in laboratory and a greenhouse. The first assessed the performance of different concentrations of 24-epibrassinolide in physiological quality of seeds and seedlings grow th in tw o lots of rice cv. IRGA 422CL. The seeds of both lots were treated with increasing concentrations of 24-epibrassinolide, zero, 0.01, 0.1, 0.4 and 1.0 µM, for a period of two hours and evaluated through the tests of germination, the first counting of germination, the speed of germination index , emergency , speed of emergency index , length of shoot and root and fresh and dry mass of shoot and root. Generally in all characteristics determined, concentrations less than or equal to 0.4 µM 24- epibrassinolide produced a positive response in physiological quality seeds of rice cv. IRGA 422CL. The second ex periment w as conducted w it h seed rice of tw o cultivars, BRS Querência, genoty pe susceptible to salinity and BRS Bojurú, tolerant to salt, in order to determine the effect of the 24-epibrassinolide on the germination, seedling grow th, leaf area and concentration of chlorophy ll under salt stress condition. Seeds w ere soaked for tw o hours in w ater, 100mM NaCl and solutions of 100 mM NaCl supplemented w ith 24-epibrassinolide at concentrati ons of 0.01, 0.1 and 1.0 µM. The viability and vigor of rice seeds of cv. BRS Querên cia w ere reduced by salinity and w ere restored by the application of the 24-epibrass inolide in concentration 1.0 µM. While in cv. BRS Bojurú the vigor w as reduced by th is concentration. The application of the 24-epibrassinolide in cv. BRS Querência incr eased the concentration of chlorophy ll, leaf area, length of root and shoot, f resh and dry mass of root and shoot, reducing the deleterious effects caused by salinity. H ow ever, in cv. BRS Bojurú, tolerant to salinity , the application of the 24-epi brassinolide 0.01 µM reversed or did not affect the characteristics of grow th, although, concentrations of 0.1 e 1,0 µM reduced the characteristics of grow th, but did not affect the chlorophy ll concentration. Based on the results, it can be inferred that the supplementation of saline solution w ith 24-epibrassinolide improves the q uality of see d varieties susceptible to salinity , not acting the same w ay in more tolerant cultivars.