THE PRELIMINARY STUDY ON THE CARBOHYDRATE AND NITROGEN METABOLISM OF DIFFERENT GROWTH DURATION VARIETIES
The carbohydrate and nitrogen metabolism of different growth duration varieties were studied and the main results obtained as summarized as follows:The dry matter production of the longer growth duration varieties was higher than the shorter ones, but it was not related with grain yield. The grain yield had close correlation with the total carbohydrate. Although the dry matter production could be increased under high N water culture, the grain yield declined because of the lower content of the carbohydrate. The varieties with shorter growth duration were more tolerant to nitrogen. Compared with the shorter growth duration varieties the carbohydrate accumulated before heading of the longer grwoth duration varieties was higher, but the translocation rate was related with the amount of the sugar at heading. Although there was no relationship between N content of leaf blade and growth duration, The content of carbohydrate in stem and leaf sheath was higher with longer growth duration varieties. In the field experiment the daily production of carbohydrate had a "higher—lower—higher" phenomenon from panicle initiation to heading, which did not appear in high N water culture.