Studies on dry matter and grain production of F1 hybrid rice in China. III. Grain-production character from the view point of time changes in non-structural carbohydrate and nitrogen contents during the yield production.

Abstract

High yielding factors of F1 hybrid rice was extensively examined from the time changes in the percent of non-structural carbohydrate (NSC%) and total nitrogen (N%) in the leaf blade, culm and leaf sheath. There was no large difference in NSC% of leaf blade (LB) between the F1 hybrid rice and common rice varieties. However, NSC% of the culm and leaf sheath (LS) in the F1 hybrid rice showed a higher value than common rice varieties. NSC% of LS in all common rice varieties decreased rapidly after the heading stage, and then increased again at the middle stage of ripening. On the other hand, that of the F1 hybrid rice continuously decreased up to the harvesting stage. There was a highly positive correlation between the decreasing rate of NSC% and translocated products from the LS during ripening period. There was also a highly positive correlation between the decreasing rate of NSC% and grain yield. These results show that NSC in the LS moves to grain and contributes greately to the production of brown grain rice. The N% of the LB is higher than that of the LS in all varieties. N% of the F1 hybrid rice was lower than that of common rice varieties in both plant parts. There was significant positive correlation between N% in the LB and grain yield when excluded the F1 hybrid rice. These results show that a high yield of the F1 hybrid rice depends more on the reserved carbohydrate accumulated in the LS before the heading stage as compared with common rice varieties.