Abstract
1. A decrease in dehydrogenase activity, which assumed as the extent of senescence, in spikelet following the progress of ripening was studied with using TTC solution in cv. Nihonbare. (a) It was found that disappearance of the enzyme activity in spikelet occurred earlier as following order; in ventral portion of endosperm in dorsal portion of endosperm in vascular bundle of rachilla and pedicel in outer layer of kernel. (b) From these results dehydrogenase activity in spikelet disappears earlier in endosperm where nutrients are accumulated and synthesized than in vascular bundle of rachilla and pedicel through which nutrients translocate to endosperm. 2. Relationships between panicle and leaf senescence was studied. (a) Panicle senescence expressed by the decrease in TTC reducing activity oc-curred much earlier in Indica varieties than in Japonica ones, irrespective of the differcnce in the speed of leaf senescence. (b) Panicle senescence occurred much later in Japonica varieties than in Indica ones. But among Japonica varieties varietal difference in panicle senescence was observed and it occurred more rapidly in the varieties in which leaf senescence occurred more rapidly. (c) Grain weight after flowering increased more rapidly and stopped earlier in the varieties in which senescence in spikelet occurred earlier.
