Effects of salinity, drought and heavy metal stress during seed germination stage in ricebean [Vigna umbellata (Thunb.) Ohwi and Ohashi]

Plants are frequently exposed to a variety of stress conditions such as drought, salinity, heavy metal toxicity, low temperature, flooding, extremes of soil pH and heat which causes reduction of plant growth and productivity. Such abiotic stresses may cause metabolic impairment, nutrient imbalance, reduced synthesis of photosynthetic pigments which are closely related with biomass production in plant, thus, causing serious loss in crop productivity. The present experiment was undertaken to study the biochemical and physiological effects of salinity, drought and heavy metal (copper and lead) stress on seed germination in ricebean [Vigna umbellata (Thunb.) Ohwi and Ohashi] variety Bidhan 1. For studying the effect of iso-osmotic potential of salinity and drought stress, the solutions of NaCl and PEG 6000 with − 0.2, − 0.4 and − 0.8 MPa osmotic potential were used whereas the solutions of 50, 100 and 200 µM Cu and Pb supplemented in the form of CuSO4.·5H2O and Pb(NO3)2 respectively were used to study the effects of equimolar concentrations of copper and lead. Drought was found to produce more adverse effects on germination %, as well as speed of germination, in the seeds of ricebean. The seed protein content was significantly higher under all the treatments of salinity, drought stress as well as metal stress. The highest intensity of copper stress was found to produce more adverse effects than lead in respect of water uptake % in germinating seeds and root elongation rates of ricebean seeds in the present experiment. The presence of copper in the germinating medium produced more detrimental effects on activities of antioxidative enzyme ascorbate peroxidase and guaiacol peroxidase than equimolar concentrations of lead.