MORPHO-PHYSIOLOGICAL AND MOLECULAR RESPONSES OF COWPEA (VIGNA SINENSIS L.) TO NICKEL TOXICITY

One of the environmental risks that threatens us is the toxicity of nickel (Ni2+). Cowpea (Vigna sinensis L.) plants require it in trace amounts, while high concentrations of it influence their biochemical and physiological processes. In the current study, the effect of various concentrations of nickel (100, 200, and 300 mg Ni2+/ kg soil) has been investigated to identify their effects on Vigna sinensis. The results revealed the negative effects of nickel on most of the studied physiological and morphological traits compared with those of the control. The concentrations of mineral elements and chlorophyll decreased significantly. Reducing, non-reducing and total sugar content were affected negatively. Furthermore, the activity of studied enzymes (APX, GPX, CAT, SOD) decreased significantly. Moreover, the negative effects of nickel concentrations on the root, stem, leaves, seeds, flowers and fruits were obvious. On a molecular level, the ISSR markers could not detect any polymorphism, indicating no toxic effect of nickel on the DNA at the studied concentrations. It is obvious that the nickel has a toxic effect on Vigna sinensis at physiological and morphological levels. The conduction of more investigations on the effects of nickel on a molecular level using more molecular markers is highly recommended.