Effect of exogenous amino acids application on growth and nutritional value of cabbage under drought stress

The present challenges imposed by environmental stress on plant productivity necessitates agronomic fortification of plants to meet global food and nutrition security food. In furtherance of this, an investigation was carried out to determine the effect of rate of application (0, 150 and 300 mg/L) of a mixture of 16 different L-amino acids, namely: L-isoleeucine, L-valine, L-threonine, L-lysine, L-phenylalanine, L-tryptophan, L-methionine, L-histidine, L-arginine, L-aspartic Acid, L-cysteine, L-glutamic Acid, L-glycine, L-proline, L-tyrosine and L-serine under two irrigation regimes (50 % and 100 % field capacity) on the nutritional value and growth of cabbage (Brassica oleracea var. capitate cv. Alba). The drought treatment reduced photosynthesis and shoot fresh and dry weights. The activities of peroxidase and catalase rose upon amino acid (AA) application under drought stress or AA3 under control regular watering, which also increased photosynthesis by approximately 250 %. AA1 and AA2 treatments increased transpiration rate by approximately 11 % and 41 % respectively under drought stress condition but declined by approximately 39 % in AA3 treated plants. There was between 10 and14 % reduction in total amino acids under the drought treatment compared to the control. AA application increased phenolic, protein and proline concentrations of the cabbage plant especially under drought condition while antioxidant was increased under control regular watering. Tissue nitrate concentration increased significantly by 50 % under drought stress condition irrespective of AA application rate. Overall, AA application at 150 mg/L was more effective in mitigating the destructive effects of drought stress in addition to the improvement in cabbage growth and nutritional value under drought stress conditions.