Drought Impacts and the Tolerance Mechanisms in Rice (Oryza sativa L.): A Review

Abstract

RICE (Oryza sativa L.) is considered the major source of calories for more than half of the world’s population. However, this Asian staple crop is susceptible to abiotic stress, including drought, throughout its life cycle. The main theme covered in this review includes types of drought and its effects on rice morphological, physiological, biochemical, and agronomical levels and their adaptive mechanisms under drought. Drought in the rainfed ecosystem during critical stages (germination and reproductive stages) has seriously undermined rice production, posing a danger to global food supply and sustainable food production worldwide. It caused a reduction in the germination rate, CO2 assimilation rate, photosynthesis activities, gas exchange via the leaf, plant height, number of panicles, seed weight, biomass, harvest index, and yield. Delayed seed germination, flowering, and maturity of the rice plant are also associated with water stress. Under mild or adverse drought conditions, plants exhibit certain adaptive changes or tolerance mechanisms, including activating antioxidant systems and the production of osmolytes such as proline and polyamine, subsequently enhancing drought tolerance. The role of phytohormones in alleviating stress has been recognized and highlighted in this review. Furthermore, the plant root system also plays a significant role in drought. The information provided in this review will help researchers to have comprehensive knowledge and understanding of the changes and disruptions that occur in rice during water stress and its tolerance mechanisms, subsequently facilitating the selection and development of drought-tolerant rice.