Modulating the antioxidant defense systems and nutrients content by proline for higher yielding of wheat under water deficit

Abstract

Numerous plant metabolites, especially amino acids, are accumulated as a result of stress. These amino acids are crucial for plant metabolism and development and have historically been viewed as the building blocks of proteins. Several studies suggested that there is a link between proline buildup and exposure plants to stress. Proline performs important functions under stress in addition to be a great osmolyte, antioxidant enzyme, acts as an antioxidant defense and signaling molecules. Two field trials were during two successive winter seasons (2020/2021 and 2021/2022). The effects of proline foliar application (0, 100, 200, 300 and 400 mg L−1) and irrigation water levels (irrigation by 100, 80 and 60% of crop water requirements, CWR, CWR100, CWR80 and CWR60, respectively) on plant pigments, antioxidants activity, yield traits and nutrient contents of wheat were assessed. The experiment was designed in a split-plot involving 4 replicates. Drought stress (CWR80 and CWR60) led to reductions in photosynthetic pigments, and yield components. Under severe water stress (CWR60), proline 200 and 300 mg L−1 recorded the highest values of chlorophyll a, chlorophyll b, and total pigments. Application of proline 300 mg L−1 was the potent practice for enhancing the antioxidant activity% (DPPH radical scavenging) and phenols content under CWR100 and CWR80. Indole acetic acid (IAA) possessed the maximum values with proline 200 mg L−1 under all irrigation patterns. Under severe deficit water (CWR60), without proline spraying (for super oxide dismutase), 200, 300 or 400 mg L−1 proline (for peroxidase) and 200 or 400 mg L−1 proline (for polyphenol oxidase) recorded the highest values. Spraying proline 300 mg L−1 achieved the highest values of grain number spike−1, weight of 1000 grains and grain yield ha−1 under different irrigation regimes. In conclusion, proline is considered a good mitigator for drought stress, due to it increased wheat plant tolerance to water deficiency throughout improving plant physiology and consequently yields quantity and quality. The most efficient concentrations of proline for coping the adverse impact of drought were 200 and 300 mg L−1.