Exogenous Myo-inositol Weakens Salinity Effects by Improving Photosynthesis, ROS Homeostasis, Osmotic Adjustment, and Nutrient Acquisition in Maize (Zea mays L.)

Abstract

Salinity significantly impairs plant growth and development, and effective strategies are required to mitigate its detrimental effects. Previous studies did not document myo-inositol (MYO) influence on vital processes such as photosynthesis, methylglyoxal production, redox balance, and ion homeostasis in plants subjected to saline conditions. The literature lacks comprehensive insights into the myo-inositol-mediated modulation of pivotal tolerance mechanisms. Hence, our study fills this significant gap by elucidating the intricate role of MYO in augmenting plant resilience to salinity stress, shedding light on its multifaceted impact on key physiological pathways essential for plant adaptation and survival. This study investigated the potential of MYO as a mitigating agent against NaCl and KCl salinity in maize plants. Two maize cultivars with differential salinity tolerance (salt-tolerant cv. Pearl and salt-sensitive cv. Malka-2016) were subjected to 12 dS m^‒1 salinity of NaCl and KCl. The findings revealed that MYO (25, 50, and 75 mg L^‒1) enhanced plant growth under salinity by improving chlorophyll content, photosynthesis, antioxidant compounds, antioxidant enzyme activities, and nutrient acquisition. Myo-inositol promoted leaf relative water content by improving osmotic adjustment due to the accumulation of osmolytes such as proline, soluble sugars, and free amino acids. MYO significantly increased nitrate reductase activity alongside higher H₂S and nitric oxide levels. These observations suggest that MYO influences plants' antioxidant capacity and metabolic responses to salinity. Notably, MYO effectively diminished reactive oxygen species generation and lipid peroxidation, thereby improving plant growth under salinity. Conclusively, MYO significantly improved growth, decreased oxidative injury and promoted photosynthesis, osmotic adjustment, and antioxidant defense system under salinity. These findings indicate that MYO is a potential growth regulator and stress mitigator, offering promising prospects for sustainable crop production in saline environments.