Effect of foliar application of indole-3-acetic acid (IAA) at the beginning of grain growth (cell division) stage on agronomic characteristics and seedling growth parameters of two bread wheat under water and salinity stresses

Despite the main role of plant growth regulators in regulation of grain growth, about the physiological roles of IAA are not similar view points. Hence, the first experiment in the research field of Razi University was applied as a split-plot arrangement based on randomized complete block design (RCBD) in three replications. Exogenous application of IAA was used at the beginning of grain growth on two bread wheat genotypes (‘Marvdasht’ and ‘Pishtaz’). Water deficiency also applied at grain growth stage. The results revealed that grain yield and all the yield parameters such as thousand grain weight decreased progressively in water deficiency at post-anthesis. In well water condition, grain yield of ‘Marvdasht’ genotype significantly was higher than ‘Pishtaz’ genotype. Water deficiency caused greater reduction in grain yield of these genotypes. These results showed that ‘Marvdasht’ genotype was more sensitive to applying of water deficiency at grain growth stage. Exogenous application of IAA at the beginning of grain growth caused significant increasing of grain yield. In the second experiment, the effect of foliar application of IAA at the beginning of grain growth was evaluate on germination percent and seedling growth parameters in wheat genotypes under different levels of NaCl salinity (0, 40, 80 and 120 mM). Based on results, salinity significantly decreased the plumule, radicle and seedling length and dry weight, germination percentage and seedling vigor index and also significantly increased mean germination time and had no significant effect on plumule to radicle ratio. Application of IAA significantly increased seedling growth parameters under different salinity levels. The evidences from this study suggest that foliar application of IAA at the beginning of grain growth with may be via increasing of grain weight and then seed vigor can increase resistance to environmental adversity in the next planting.

Wheat, grain yield, water deficiency, grain filling, phytohormones, salinity