Study of the Interactive Effects of Calcium and Abscisic Acid on Drought Stressed Triticum aestivum Seedlings

Abstract

IN THEIR natural habitats, plants are continuously subjected to many severe environmental challenges including drought. In this study, the effects of drought on Triticum aestivum seedlings were assessed, and the alleviating roles and interactive effects of calcium (Ca2+) and abscisic acid (ABA) to drought stress were studied. The results showed that pretreating wheat seedlings with calcium chloride (CaCl2) or ABA led to alleviating most of the negative effects of 20% polyethylene glycol (PEG, as a drought imposing agent). Ca2+ improved the growth criteria, photosynthetic activity, but ABA had no significant effects on growth parameters. Ca2+ or ABA pretreatments have alleviated the toxic effects of the drought-induced oxidative stress which was marked with the reduction of MDA content. Ca2+ and/or ABA reduced the PEG-induced catalase activity, and ascorbic acid content. The use of lanthanum chloride (LaCl3) as a calcium channel blocker has confirmed the role of Ca2+ in ameliorating the drought effects on plant. This study revealed that the application of Ca2+ has increased the endogenous ABA level of the treated seedlings to a high extent exceeding that of PEG treatment itself suggesting that ABA requires Ca2+ ions for its induction, and ABA is working downstream from Ca2+ in the relevant signaling pathways activated by drought stress. The alleviating effects of Ca2+ was prolonged to the yield stage. Overall, our results suggest that Ca2+ (10 mM), and with a less extend ABA (0.1 mM), represent signaling agents that can partially alleviate drought stress in plants growing in dry environments.