PHYSIOLOGICAL SCREENING ON VEGETATIVE GROWTH ASPECTS OF TWO VARIETIES OF Vigna SPP (COWPEA) AS INFLUENCED BY WATER STRESS

Cowpea, Vigna unguiculata (L.), a dicotyledonous plant belonging to the family Fabaceae, and genus Vigna is a major and important leguminous crop which serves as a source of livelihood to the millions of people in the tropics. Plants experience water stress either when the water stored in their roots becomes limiting or when the transpiration rate becomes high. Water stress is primarily caused by the water insufficiency, i.e. drought or tremendous soil salinity. Experiments were carried out to examine the effects of water stress on some growth aspects of two varieties (Brown (B) and White (W)) of Vigna unguiculata (Cowpea). The study was conducted for three (3) months from April to June 2017 in Gombe State University Biological garden. The two varieties were divided into two (2) categories of the stress treatments; that is Control (W1 and B1), Mild stress (W2 and B2) and Severe stress (W3 and B3. The watering regimes of every day (Control), twice a week (Mild stress) and once a week (Severe stress) of four replicates each, making a total of forty-eight (48) pots under the different stress categories including the Control were investigated. The seedlings were grown in the Biological Sciences garden (Gombe State University campus). The growth parameters studied were plant height, leaf length, leaf width and leaf area, number of leaves, root dry weight, shoot dry weight, and relative water content. Results of this study showed that the two varieties of cowpea were significantly (P<0.05) affected by water stress. The highest growth performance was observed in the control (W1 and B1) and mildly stressed (W2 and B2) seedlings which were watered daily and twice a week respectively while the growth performance in the stressed varieties (W3 and B3) was significantly reduced. The treatment showed adverse effect on brown variety than white variety in terms of relative water content. Water stress is therefore an important factor to be considered during the growing stage of Vigna unguiculata as depicted by the morphological/physiological parameters measured in the current study.