Effects of seed priming on biochemical parameters and seed germination in cowpea [Vigna unguiculata (L.) Walp]

Cowpea seeds lose their vigour during storage at high temperature and high relative humidity. Present study was conducted to invigorate the performance of high and low vigour seeds (exposed to 45 +/- 2 degrees C and 100% RH) by seed priming with different chemicals and concentrations (GA(3) (100ppm). CaCl2 (10-3M). Ammonium Molybdate (10(-3)M); KBr (10(-3)M); Mg (NO3)(2) (10(-3)M); ZnSO4 (10(-3)M); hydro primed and dry seed (control) at 15 degrees C for 24 hours. Priming was effective in reducing the time for 50 % germination and mean germination time and increased the germination percentage in low vigour seeds, while energy of germination and final germination percentage in normal seeds displayed a minor increase. Priming of normal / low-vigour seeds improved the vigour of seedling in terms of seedling length and their dry weight and seedling vigour index. Seed priming of fresh and accelerated cowpea seeds increased the electrical conductivity of seed leachate, cell membrane stability, total protein content, a amylase activity, peroxidase activity and dehydrogenase activity over control dry seeds. Esterase and peroxidase enzymes were completely lost as a result of accelerated ageing, which showed reappearance after priming. Priming showed little improvement in the banding pattern and intensity of enzyme in normal seeds.