Biochemical and molecular responses of oilseed crops to heavy metal stress

Oilseed crops are of great importance due to their economical and nutritional value. They are the largest source of edible oil. Their demand is increasing gradually with the passage of time. Heavy metals accumulation is a universal problem and has many ecological and biological effects. Their concentration beyond certain limits effect oilseed crops. Under heavy metal stress, plants generate reactive oxygen species that are injurious to biomolecules. Plants have antioxidant defence system to cope with heavy metal stress. It has been found that heavy metals are less harmful or necessarily required to plants at lower metal concentration but at higher concentration, they are found toxic. Different heavy metals effect exhibit varied responses on biochemical and molecular responses of oilseed crops. It was found that different heavy metals like Cd, Cr, Zn, Pb and Cu etc. negatively affect antioxidant defence system consisting of superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), glutathione reductase (GR), mono dehydro ascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) and lower molecular weight compounds like proline, glutathione, thiol, ascorbic acid etc. These metals also showed harmful effect on biomolecules (total proteins, nucleic acids, lipids and amino acids etc.). They also negatively affect plant growth parameters, chlorophyll contents. Some positive relationships were also noted in plant responses at early growth stages and at lower metal concentrations.