Effects of water stress on the growth and reproduction of black gram (Vigna mungo l.)

Black gram ( Vigna mungo L.; Fabaceae) is one of the most highly prized pulses in tropical countries especially in India. The green pods are eaten as vegetable and they are highly nutritious. Grain legumes play a vital role in improving soil health through biological N fixation and are the cheapest source of dietary protein for human and livestock. Their yield is low and unstable due to water stress during growth stages. Low rain fall with concomitant high temperature along with the increased solar radiation due to reduced cloud cover is responsible for limited water supply to crops in many tropical regions which results in shortages of black gram around the world. Water is a primary input not only in enhancing the crop production but also involved directly or indirectly in all the physiological processes in plants which directly changes morphological characters of plants. In the present study changes in morphological characters due to the ten-day water stress were observed at vegetative and reproductive stages (flowering stage and fruiting stage). All characters observed viz. plant height, wet and dry weight of shoots and roots, root length, number of pods, wet and d ry weight of pods, wet and dry weight of seeds were significantly affected by the water stress condition. Water stress at vegetative stage seriously limited the plant height, wet and dry weight of shoots and roots and root length, whereas water stress at reproductive stage showed clear impact on the number of pods, wet and dry weight of pods, wet and dry weight of seeds. The least plant height (46.76cm) and root length (15.98 cm) were observed at vegetative stage under water stress while control plants showed 88.89cm plant height and 21.85 cm root length. The reduction of the number of pods per plant was more pronounced under soil moisture stress at the flowering stage compared to that under fruiting stage. Therefore, the least number of pods per plant, 2.04, and wet weight of seeds per pod, 0.0031 g, were ob-served in plants stressed at flowering stage while plants under controlled conditions showed 14.9 pods per plant and 0.0907 g of seed wet weight per pod . Water stress at fruiting stage resulted in a wrinkling appearance of seeds with unfilled grains. Number of root nodules was reduced significantly due to drought condition at vegetative stage compared to that under reproductive stages. Tropical Agricultural Research and Extension 17(1): 2014: page 45-48