Study on Physiological Response during Seed Maturation and Optimal Harvest Time of Bromus cartharticus

In order to investigate the physiological response during Bromus cartharticus seed maturation and determine the suitable harvest conditions and time, the indexes including water content, grain weight, storage substance content, enzyme activities and ATP content of B. cartharticus varieties Jiangxia and Qiannan during seed maturation were studied. The results showed that with the maturity of seeds, water content continued to decrease, but the maximum water loss rate had a great difference among these varieties. The water loss rate of Jiangxia was the highest at 33 to 38 days with 4.94% decline per day, while that of Qiannan was the highest at 38 to 43 days with 6.45% decreasement per day. The change of dry weight content was opposite to water content, and the dry weight of Jiangxia and Qiannan reached physiological maturity on the 38 th day after flowering, which were 1.22 g and 1.36 g, respectively. In addition, the 1 000-grain weight was relatively high（11.25 g and 14.13 g） on the 33 rd day after flowering, and the variation of grain weight was related to variety ripening and shattering trait. Soluble sugar content increased gradually and reached the maximum value(112.80 mg·g^-1 and 106.76 mg·g^-1 respectively) on the 13 th day after anthesis, then began to decrease, and tended to be stable on the 33 rd to 43 th day after flowering. And the change of starch content was basically complementary to soluble sugar content. The relatively high ATP content was mainly the rapid increase stage of grain, and the change of dehydrogenase activity was not significant during seed maturation. In conclusion, Jiangxia had the best harvest on the 33 rd day after flowering, while Qiannan had a delay of 2 to 3 days.