Interspecific difference in growth perenniality in rice cultivars, Oryza sativa L. and O-glaberrima Steud.

Of the two rice cultivar species, Oryza sativa and O. glaberrima, the former was predicted as a species with a higher potential in growth perenniality compared to the latter in a previous paper. in this paper we made a further study to confirm the specific difference in growth perenniality by comparing the growth characteristics, leaf photosynthesis and photosynthate partitioning in a plant at the post-heading stage. O. glaberrima was characterized by quick accumulation of photosynthate in the panicles. The simple,lf: morphological formation of rachis branching of O. glaberrima is thought to allow the smooth transportation of photosynthate from leaves to chaffs of a panicle and the early maturation. Such a feature as observed in O. glaberrima is regarded as an advantageous character for the seed production in annual plants. The photosynthate partition among different organs was monitored by the C-13 trace method. The culm base of O. sativa accumulated several-fold more C-13 than that of O. glaberrima. The accumulated photosynthate is available as energy resource for initiation of the regenerative growth by ratooning, and the species having a large amount of the accumulation can keep a high potential of growth perenniality.