Effect of nutrient application and water turbidity on submergence tolerance of rice (Oryza sativa L.)

Abstract

Flooding imposes severe selection pressure on plants, principally because excesswater in their surroundings deprives the plants from certain basic resourcessuch as oxygen, carbon dioxide and light for photosynthesis. Here, the effectsof nitrogen and phosphorus application and their application time, on fourIndicarice cultivars and their tolerance to submergence under turbid and clearflood water was studied. Submergence tolerance on metabolic changes, photo-synthetic (Pn) rate and ethylene accumulation were evaluated. Submergencesubstantially reduced survival, chlorophyll, soluble sugars, Pn rate across culti-vars with drastic reduction in IR-20.Sub1cultivars showed greater Pn rate ascompared to sensitive cultivar under submergence because of better protectionof chlorophyll, more stomatal conductance leading to higher survival. Turbidwater resulted in lower under-water photosynthesis because of poor light trans-mission, chlorophyll retention and silt deposition and ultimately poor survival.Foliar spray of N after desubmergence along with basal P improved the chloro-phyll, soluble sugars and Pn rate and extenuated ethylene accumulation andshoot elongation resulting in significantly higher survival. To the best of ourknowledge, this is the first time that such a study has been performed. Cropestablishment could therefore be enhanced in areas where untimely floodingis anticipated by applying basal P and foliar spray of post-submergence N