PHYSIOLOGICAL, BIOCHEMICAL AND ANATOMICAL RESPONSES OF COWPEA (Vigna unguiculata L. Walp) VARIETIES EXPOSED TO SALINITY STRESS

Abstract

Salinity induces Reactive Oxygen Species (ROS) which leads to oxidative damage in various cellular components. Plants in turn develop various physiological and biochemical mechanisms in order to overcome salinity stress. The purpose of this research was to investigate the effect of salinity stress on the growth, biochemical and anatomical responses of cowpea. In this study, two varieties of cowpea were planted in 48 perforated pots and these were treated separately with Sodium chloride (NaCl) and Sodium tetraoxosulphate (vi) (Na2SO4) salts at electrical conductivity of 0, 5, 10 and 15 dS/m. The experiment was carried out in a screen house. The parameters that were investigated in the study included the physiological, biochemical and anatomical responses. The results from the study were subjected to Two-Way Analysis of Variance (ANOVA) and the means were separated using Duncan’s New Multiple Range Test (DNMRT). The result revealed that decrease in leaf diameter could be attributed to reduction in nutrient assimilation rate. The observed higher leaf length at 5dS/m under NaCl relative to the control suggested that plants growing under salinity stress responded by devoting more of their available carbon to shoot growth resulting in elongated stems. Accumulation of osmolytes conferred structural stability to cellular membrane by detoxifying reactive oxygen species (ROS) thereby mitigating oxidative damage. The increased Malonaldehyde content in Ife Brown (IFB) under NaCl and Na2SO4 treatment indicated that IFB is capable of maintaining high degree of cell membrane homeostasis under high salt stress. The reduced activity of superoxide dismutase (SOD) and Gluthathione (GSH) content in Ife BPC (IBPC) demonstrated that enzymatic and non- enzymatic antioxidants are capable of scavenging reactive oxygen species thereby mitigating salinity induced oxidative damage in cowpea. Anatomical modifications in the stomatal apparatus was attributed to the tendency of the apparatus to compartmentalize and sequester the toxic ions in vacuoles.