Growth, nutritional status and nitrogen metabolism in Vigna unguiculata (L.) Walp is affected by aluminum

Abstract

Al toxicity is one of the most important abiotic stresses that reduce the growth and development of plants. From a physiological standpoint, Al affects the activity of several important enzymes such as nitrate reductase, which is the gateway of nitrogen in plants, and also triggers nutritional disorders and reduced plant growth. The content of nitrogen compounds, macronutrients and growth were assessed in order to better understand how cowpea plants respond to the toxicity of Al in a nutrient solution. The study was conducted in a greenhouse in a completely randomized design, consisting of the concentrations of 0 and 1 mM of Al. After ten days of applying the treatments we evaluated the activity of nitrate reductase, concentrations of protein and total soluble amino acids, proline, ammonia, macronutrients, and dry weight of the shoots and roots. Al reduced the nitrate reductase activity (-16%), concentration of nitrate (-22%), protein (12%) amino acids (-14%) and proline (-66%), however the concentration of ammonia increased (27%). Similarly, among concentrations of macronutrients that of calcium was most reduced (-21%), followed by magnesium (-16%) phosphorus (-19%) and potassium (-18%). The production of shoot and root dry matter was reduced by 18 and 27% when applying Al. The cultivar of cowpea Pretinho precoce 1showed to be sensitive to Al toxicity as a result of its inability to promote a biochemical response and satisfactory nutritional production when subjected to Al toxicity, which justifies the need for adoption of liming processes in the production of this cowpea crop which is appreciated by small agricultural producers in the North and Northeast regions of Brazil.