Effects of Sucrose Concentration and Hormones on the Grain Development of Detached Rice Panicles in vitro Culture

The influences of sucrose concentrations and different kinds of plant hormones on the solution and sucrose absorption and dry matter accumulation were invcstigated, with detached panicles of three different source-sink types of rice varieties cultured for 10 days in liquid culture. The results indicated that, with the some range of sucrose concentration, the volume of solution taken up by the grains increased with the increment of sucrose concentration, and decreased when the sucrose concentration was 320 mmol/L for Yayou 2 and Shanyou 63 and 160 mmol/L for Yanjing 2. Increasing the sucrose supply in the liquid culture from 20 to 320 mmol/L resulted in significant increase in the sucrose absorption by grains of all three rice varieties. When the sucrose concentration was between 20 and 160 mmol/L, the dry matter and starch accumulation of grains was stimulated by increasing sucrose supply, but when the sucrose concentration was higher, the dry matter and starch accumulation of grains of Shanyou 63 and Yanjing 2 was inhibited. The solution and sucrose uptake and dry matter and starch accumulation were regulated by plant hormones, but there were significant differences in the re sponses of rice varieties to hormones. It suggested that the sucrose and water moved to the grains be both dependently and independently, and sugar accumulation by grains be determined by grain sink strength as well as carbohydrate supply. The possible regulation of hormones on these processes was also discussed.