Calcium channels and membrane disorders induced by drought stress in Vicia faba plants supplemented with calcium

Vicia faba plants were grown under drought conditions and variously supplemented with calcium. Drought stress markedly inhibited the growth of Vicia faba plants. Ca²⁺ ameliorated to a large extent this inhibition; fresh weight, dry mass, chlorophyll and water contents were variably improved. Membranes were, also, negatively affected by drought stress and percentage leakage was elevated. Concomitantly, the efflux of K⁺ and Ca²⁺ was enhanced by drought but lowered by supplemental Ca²⁺. In addition, membranes of droughted plants were sensitive to the Ca²⁺ channel blockers lanthanum, nifedipine or verapamil more than those of control plants. These blockers significantly increased the efflux of K⁺ and Ca²⁺ as well as percentage leakage particularly in those of droughted plants. The above results indicated that the functioning of the calcium channels was negatively affected when Vicia faba was grown under drought conditions. However, much of the drought-induced disorders including sensitivity towards the applied calcium channel blockers could be ameliorated by supplemental Ca²⁺.