Strategies to overcome drought stress for improving plant growth under sustainable agriculture

Drought stress is an unavoidable factor that exists in a variety of habitats which hinders the production, quality, and energy of plant biomass. Drought conditions result in oxidative stress in plants due to excessive reactive oxygen species (ROS) produced as a result of low CO2 which interferes with plant photosynthetic capacity. Consequently, during periods of drought stress, the transport of nutrients and the mass flow of water-soluble nutrients like nitrate, sulfate, calcium, and silicon is reduced. The application of traditional approaches in developing drought-tolerant crops is a time-consuming process, and the use of advanced biotechnology for agricultural development is still viewed with caution. The use of plant growth-promoting rhizobacteria (PGPR) as a cost-effective and environment friendly strategy can be adopted to enhance crop development in drought stress conditions. The synthesis of 1-aminocyclopropane-1-carboxylate (ACC) deaminase promotes plant nutrient uptake by metabolizing plant ACC, consequently preventing the accumulation of ethylene. The PGPR enhances the plant's defense mechanisms, leading to higher relative water content, decreased oxidation products and increased levels of antioxidants and osmo protectants within the plants. The synthesis of exopolysaccharides (EPS) also improves the soil's capacity to retain water. Osmolyte synthesis is increased by PGPR and effectively mitigates ROS's harmful effects to assist the plant growth. For the manufacture of bio-fertilizers to minimize the negative impacts of drought stress on crops grown in dry environments, multifaceted PGPR are promising options. This review outlines potential future directions for sustainable agricultural production and suggests techniques to improve their effectiveness as bio-inoculants in field settings.