Role of silica and nitrogen interaction in submergence tolerance of rice

• We hypothesized tolerance to submergence with nitrogen and silica interaction in rice.
• Under oxidative stress induced after submergence, photosynthesis and growth was affected resulting in poor survival.
• The SUB1 cultivars tolerated submergence by reserving carbohydrates and chlorophyll and maintenance of antioxidants.
• Plants fed with basal silica and post-flood nitrogen had higher survival because of less lodging, senescence and higher antioxidants.

Submergence is an intensifying problem in major rice producing areas, when intolerant cultivars are submerged, they show a number of morpho-physiological changes such as elongation and chlorosis which is markedly developed after desubmergence probably due to oxidative damage. We studied the effects of submergence on survival, photosynthesis, nonstructural carbohydrate content, enzymatic activities, growth and yield of Sub1 and non-Sub1 cultivars. The interaction effect of nitrogen (N) and silica (Si) application was also examined for the submergence tolerance in rice. The photosynthetic rate, survival, growth of all the cultivars decreased during submergence but to a greater extent in IR64 and Swarna. After desubmergence, both the type of cultivars experienced oxidative damage, however, the oxidation of lipids was maintain at lower levels in Sub1 cultivars and anti-oxidants activities was increased more than intolerant cultivars. Application of basal Si was beneficial whereas, pre- and post-submergence Si spray was detrimental in relation to submergence tolerance. Basal Si resulted in significantly reduced elongation, lodging, leaf senescence, and chlorosis; when combined with post-flood N application either as broadcasting or spray, it led to significantly highest survival, photosynthesis, anti-oxidant activity and ultimately yields. Interaction of basal Si and post-flood N spray was the most promising method of nutrient application which not only resisted the damage during submergence but also enhanced the survival, growth after recovery in terms of number of green leaves emergence, leaf area and photosynthetic rate leading to significantly higher yield. The findings of the investigation propounds that a simple alteration in the time and method of nutrient application can significantly contribute to higher survival, crop establishment and yield in flash-flood prone areas.