The Effect of Proline and Salicylic Acid on the Physiological Parameters and Yield of Silage Maize under Different Moisture Regimes

Water resources are limited. Thus, one of the ways to prevent the decline of maize yield under water shortage conditions is the use of growth regulators. In this study, the effects of proline (150 mg/L) and salicylic acid (0.5 mmol) on the yield and water use efficiency of maize were investigated under three irrigation regimes, including complete irrigation (control), 75% of complete irrigation (mild stress) and 50% of complete irrigation (severe stress). The experiment was performed as a split plot in a randomized complete block design with three replications in 2016. The results showed that drought stress significantly reduced the relative water content, chlorophyll and carotenoids concentrations, leaf area index, leaf weight, stem weight, ear weight, yield, and water use efficiency, as compared to complete irrigation. However, the extent of the drought-induced decreases in the latter traits varied, such that the smallest and greatest decreases were found in leaf area index (9.66%) and the carotenoids concentration (78%), respectively. According to our results, although drought stress suppressed maize yield and its components, the application of proline under mild drought stress led to the improvment in forage yield and water use efficiency by increasing the leaf relative water content and partial amelioration of the suppressions in leaf, stem and ear weights. Foliar-applied proline indicated a greater efficacy in ameliorating drought stress effects on forage yield and water use efficiency, compared to foliar-applied salicylic acid. Therefore, foliar application of proline is potent to be adopted as a suitable criterion to increase tolerance to drought stress in silage maize.