Silicon as attenuator of excess ammonium in papaya seedlings

Abstract

The excess of ammonium has a harmful effect on plant development, however the use of silicon can reduce its toxicity. Given the above, the objective was to characterize the symptoms of ammonium toxicity, diagnose its effects on the growth and nutritional status of papaya seedlings, and verify the effect of silicon as a stress reliever. The experiment was carried out in a greenhouse at UNESP – Campus de Jaboticabal-SP, Brazil. The experimental design used was a randomized block design in a 4x2 factorial scheme, with four concentrations of ammonium (7.5, 15, 30 and 60 mmol L^-1), and in the absence and presence of silicon, with four replications. The silicon source used was monosilicic acid and the ammonium source was ammonium chloride. Visual symptoms of ammonium toxicity, evaluations of plant height, stem diameter, green color index, leaf area, electrolyte leakage, shoot and root dry matter were characterized, and N, Ca, accumulation was also calculated. Mg and K in shoots. The excess of ammonium resulted in visual symptoms of toxicity, namely: reduced growth, leaf necrosis in older leaves, chlorosis and wrinkling in younger leaves. There was an increase in electrolyte leakage and resulted in less nutrient absorption. Silicon acted as a beneficial element in mitigating the physiological stress caused by excess ammonium.