PLANT CELL BIOTECHNOLOGY AND MOLECULAR BIOLOGY

Increasing temperatures may accelerate crop growth, reduce grain filling, and make crops sterile at sensitive growth phases, threatening crop yields, although higher CO₂ has the potential to enhance photosynthesis and water-use efficiency, especially in C3 crops such as rice. Rice (Oryza sativa L.) is a staple grain crop that has a high contribution to food security in the whole world, but also a major contributor of greenhouse gases (GHG), especially methane (CH₄) and nitrous oxide (N₂O). Factors of climate change, like high carbon dioxide (CO₂) levels in the atmosphere and temperature increases, have significant impacts on the physiological activity of rice, the activity of soil microbes, and the cycling of nutrients that, in turn, affect the GHG emission of paddy fields. This review summarizes existing findings on the effect of high CO₂ and temperature on CH₄ and N₂O flux in rice ecosystems individually and in a combined manner. It has been observed that high CO₂ increases biomass production, root exudation, and soil microbial activities, thus affecting the generation of methane, but temperature rises promote decomposition of organic matter and conversion of nitrogen to methane and nitrous oxide. The different experimental and field-based studies and simulation models, including Denitrification-Decomposition (DNDC), Daily time-step version of the CENTURY ecosystem model (DAYCENT), and Agricultural Production Systems Simulator (APSIM), that have been employed to forecast the future trends of emissions and the effectiveness of mitigation strategies are also discussed. The results indicate that climate variables and soil processes are highly interconnected, and integrated management practices are necessary to ensure productivity and sustainability of the environment. The review wraps up by determining research gaps, such as the necessity of long-term field tests, further parameterization of the model, and site-specific methods of mitigation that include water and nutrient management. There should be increased long-term monitoring and modeling activities to learn more about the dynamics of emissions, as well as develop policies that will help mitigate the role that agriculture contributes to global warming. Further interdisciplinary studies and mechanisms that involve farmers will be very important in balancing productivity and mitigating the climate.