Seedling size and varietal characteristics as the tools for avoidance to submergence stress at seedling stage in rice

The survival and regeneration ability were improved in heavy seedling (low seed rate/unit seed bed area) than that of thin (high seed rate) and medium (intermediate seed rate) category of rice seedlings subjected to complete submergence stress. Heavy seedlings could maintain better shoot and root fresh weight than that of other two category seedlings. The traits for avoidance to submergence stress exhibited by the cultivars had been identified to be slow or minimum degradation of dry matter, chlorophyll content and rapid elongation ability during inundation period. The cultivars with high count of survival ability after the relief of submergence stress had the lower tissue water potential (r = -0.47). TTB 202-4 was identified to be a potential rice cultivar to avoid submergence stress during seedling stage.