Morphological, physiological and biochemical aspects of zinc seed priming-induced drought tolerance in faba bean

Faba bean (Vicia faba L.) productivity is limited by drought stress and is often associated with mineral nutrient deficiencies such as zinc (Zn). Three independent experiments were conducted to optimize Zn application and its role in tolerance against drought in faba bean. In the first experiment, faba bean seeds soaked in aerated 0.001, 0.01, 0.05, 0.1 and 0.5 M Zn solutions (osmopriming) or water (hydropriming) for 12 h were sown in Petri plates in a growth chamber. Based on the results, in the second and third experiments, faba bean seeds were subjected to osmopriming with 0.001 M Zn solution and hydropriming followed by surface drying and re-drying of seed to the original weight. In third experiment, treated faba bean seeds were planted in peat moss-filled pots maintained at 75 % water holding capacity (WHC) (well-watered) or 50 % WHC (drought stress). In the first study, seeds primed with high Zn concentration (≥ 0.01 M Zn) did not germinate. Drought stress suppressed the seedling emergence, growth with enhanced oxidative stress. However, seed priming with 0.001 M Zn solution followed by surface drying ameliorated the adverse effect of drought stress by increasing the biomass production (99.8 %), leaf area (23 %), α amylase activity (85 %), soluble sugar (54.7 %), Soil Plant Analysis Development (SPAD) value (48.7 %), leaf Zn concentration (79.8 %) with reduction in leaf malondialdehyde (42.7 %) content and total antioxidant activities (35.2 %) under drought stress compared to untreated control. Conclusively, adequate Zn supply through seed priming can help in ameliorating the adverse effect of drought stress in faba bean during the early seedling growth stage.