Ni Induction Changes to Some Biochemical Traits and Protein Electrophoresis Pattern of Corronilla varia under Hydroponic Culture

Nickel (Ni) is an element which has been added recently to the list of necessary micronutrients for plants. But, as a heavy metal, especially at high concentrations, it causes oxidative stress in plants. Knowledge of physiological and biochemical responses of plants to Ni stress can help to understand the mechanisms of adaptability. The effects of Ni on chlorophyll content, proline, soluble proteins and protein electrophoresis pattern were investigated in 40 day-old Coronilla Varia plants grown in hydroponic condition in Hoagland solution that was treated with 0, 2.5, 5, 7.5 and 10 mM NiCl2. After 24 and 72 hours, the chlorophyll content, proline, soluble proteins and protein electrophoresis pattern of leaves were measured. Results revealed that chlorophyll a, b and total chlorophyll content of leaves declined progressively under Ni stress at both times. But this change was more sensible after 72 hours. A significant increase of proline content was detected in leaves after 24 and 72 hours exposure to Ni. In general, increase of proline content was more pronounced in shorter exposures to Ni, which could be due to the adaptation of plants to Ni stress in longer durations. The soluble protein content of leaves was reduced significantly with increasing Ni stress. Protein electrophoresis pattern was changed in Ni treatments; at higher Ni concentrations, the 72 and 250 k Dalton bands disappeared and 95 and 130 k Dalton bands were appeared. The results of this research discuss the contradictory effects of Ni on accumulation of chlorophyll and protein content with respect to proline.