COMPARISON OF GROWTH PATTERN AND PHENOTYPIC PLASTICITY BETWEEN WILD AND CULTIVATED RICE STRAINS

Abstract

The objective of the present study is to observe differences in growth pattern and phenotypic plasticity among wild and cultivated rice strains. Six wild (Oryza perennis) and four cultivated (O. sativa) strains were observed under various conditions. The growth pattern or the pattern of sequential changes of growth rate appeared to be characteristic of the strains. Annual wild strains showed vigorous growth for a short period around the heading time, while perennial wild strains seemed to continue vegetative growth after heading. Cultivars generally had a higher growth rate than the wild strains. In annual wild strains, the elongation of first and second internodes that usually results in heading in other strains took place after heading to lift up the panicles higher. This may help the plants to disperse seeds. They also showed a low elongation rate in the seedling stage, which appeared to be associated with prostrate habit and vigorous root growth. Phenotypic plasticity was measured in terms of standard deviations of mean character values recorded under different conditions (converted into logarithms). In the size of various organs, wild strains, particularly of perennial type, were highly plastic as compared with cultivars, though the latter were more responsive to nutritional conditions in panicle number per plant.