Indole-3-Acetic Acid Induces Biochemical and Physiological Changes in Wheat under Drought Stress Conditions

Impact of foliar application of indole-3-acetic acid (IAA) was studied to induce drought tolerance in commercially important wheat cultivars. Four hexaploid wheat (Triticum aestivum L.) cultivars viz. Aari, Baras, Sahar and Aas were grown under controlled conditions. Plants were subjected to drought stress 14 d after germination. After 21 d, 80 ppm solution of IAA was used for foliar application. Sugar and proline contents increased due to drought stress in all four wheat cultivars. Exogenous application of IAA had a varying effect on sugar and proline contents. Protein content, abiotic tolerance index (ATI) and stress tolerance index (STI) showed variation among different varieties under drought stress conditions and after IAA foliar application. Under drought conditions, relative water content (RWC) and fresh weight of wheat seedlings decreased significantly; which were recovered in the tolerant variety Aas through the foliar application of IAA. Exogenous application of IAA showed variable effects on antioxidant system. The activity of peroxide dismutase (POD) remained unaffected in the four cultivars, while superoxide dismutase (SOD) was promoted in all cultivars except Baras. After foliar application of IAA, drought-stressed plants of Aas variety showed 10.3% improvement in fresh weight compared with the untreated plants. These results lead us to conclude that IAA showed a positive cultivar specific effect in wheat drought tolerance. IAA not only helps plants to accumulate proteins, but it also restores plant fresh weight by increasing relative water content. These results suggest exogenous application of IAA to recover wheat plants from drought stress conditions.