RESUMO
A considerable progress in plant breeding for higher yield is attained mainly through selection of morpho-physiological attributes in rice. The field experiments were conducted at three different locations under sub-tropical conditions with four early maturing rice varieties viz., Binadhan-7, Binadhan-17, BRRI dhan33, and BRRI dhan39 during kharif-2 rice season (Aman; July-October) of 2016 to find out the natural variation in the morpho-physiological attributes contributing to higher grain yield in rice. Morphological parameters on plant height, root structure, tillering ontogeny, internode elongation pattern, flag leaf length, flag leaf width, flag leaf angle, number of primary & secondary rachis, branches and also physiological traits on chlorophyll content, photosynthesis rate, total dry mass, growth rate, number of vascular bundles, harvest index with yield and yield contributing characters were studied. Results indicated that plants having rapid growth and development at early growth stages showed higher chlorophyll content, photosynthesis rate, long flag leaf, number of vascular bundles in 1st internode and also exhibited the increase in the number of grains per panicle resulting higher grain yield. Among the test varieties, Binadhan-17 showed superiority in the most morpho-physiological criteria and higher number of vascular bundles manifesting in higher grain yield. This information may help breeders to identity and develop high yielding rice variety.