Augmentative Role of Salicylic Acid and Proline in Overcoming Waterlogging Stress in Sweet Corn (Zea mays var. saccharate)

Abstract

Waterlogging increasingly threatens plant growth and food security, resulting in significant yield losses. Recent research has emphasized regulatory compounds as effective solutions to alleviate abiotic stress. However, previous studies have investigated the effects of salicylic acid (SA) on sweet corn, limited research has comparatively examined the roles of SA and proline (Pro) in sweet corn under waterlogged conditions. This study aims to address this gap through a controlled pot experiment conducted under a rain shelter. This research evaluated the effect of exogenous SA and Pro on grain yield, ear characteristics, photosynthesis, total soluble solids, ion balance, and antioxidant activities in sweet corn (Zea mays var. saccharate) under different durations of waterlogging stress (3, 6, and 9 days) at the seedling (V3) and tasseling (V6) stages, with non-waterlogged (NWL) as control (CK). Waterlogging during V3 significantly reduced grain yield and other traits, with 9 days causing the greatest decline; grain yield dropped by 56.4%, 38.3%, and 41.0% for CKxV3 x 9d, SAxV3 x 9d, and ProxV3 x 9d, respectively, compared to CKxNWL. On average, SA and Pro boosted the grain yield by 10.9% and 11.5%, respectively. After 9 d of stress, sweet corn exhibited a decline in stomatal conductance (47.0%), chlorophyll (20.8%), and ear weight (28.8%), although SA and Pro reduced malondialdehyde and enhanced antioxidant activities. Exogenous SA and Pro improved the K+/Na+ ratio by 15% and 25% and the Ca2+/Na+ ratio by 13.7% and 18.8%, respectively. Foliar application of SA or Pro enhanced photosynthesis and ion balance, thus improving hypoxia tolerance. Overall, Pro was more effective than SA in enhancing sweet corn yield and tolerance to waterlogging, presenting a viable strategy for farmers to mitigate yield losses in waterlogged conditions.