Genotype-dependent responses of wheat (Triticum aestivum L.) seedlings to drought, UV-B radiation and their combined stresses
Experiments were conducted under controlled conditions to investigate the growth and physiological - biochemical responses of wheat (Triticum aestivum L.) seedlings to UV-B, drought, and their combined stresses. Both UV-B and drought treatments retarded seedling growth with UV-B having worse impact on wheat plants. Chlorophyll content and relative water content (RWC) in leaves, as stress makers, were significantly affected by UV-B and drought, respectively. The increased rate and amount of H2O2 were stress-different and genotype-dependent. Likely, the temporary expression patterns of antioxidant enzymes (superoxide dismutase, SOD, and catalase, CAT) and compounds (proline, and ascobate acid, AsA) exhibited differences under the tested stressful conditions in the two genotypes, indicating that they play significant roles in plant responses to these stresses. Pre-application of either stress reduced the damage caused by subsequent application of the other stress, and this induced defense was greater by UV-B than by drought. Compared to the stress applied separately, the combined application of drought and UV-B at the same time resulted in more adverse effects on the wheat seedlings of the susceptible variety, and more positive effects on the tolerant wheat genotype. These results provide novel insights into understanding the cellular and molecular mechanisms responsible for plant tolerance to various stresses and their interactions.
Key words: Wheat (Triticum aestivum L.), UV-B radiation, drought, combined stress, antioxidant system, genotype.