Impact of Low Canopy, Root Temperature, and Drought at the Booting Stage on Yield, Grain Quality, Photosynthesis, and Antioxidant Responses in Rice

Rice yield is significantly affected by low temperature and drought stress. This study investigated the effects of low canopy and root temperature and/or drought stress on yield, quality, biomass, photosynthesis, and antioxidant responses in different rice genotypes viz., Huahang 31 and Yuejingsimiao 2 at the booting stage. The experiment included eight treatments, that is, the natural growth condition (T0) as a control, canopy low-temperature (CL), root low-temperature (RL), root drought (RD), and a combination of stresses. The results revealed that the RL and combined stress (CL&RL, RL&RD, and CL&RL&RD) treatments significantly decreased the yield and quality, with the CL&RL&RD treatment significantly reducing the yields of Huahang 31 and Yuejingsimiao 2 by 75.49% and 65.25%, respectively. The RL and combined stress (CL&RL, RL&RD, and CL&RL&RD) treatments significantly affected the photosynthesis parameters and increased the stem sheath dry weight while decreasing the panicle dry weight, thereby affecting rice biomass accumulation. Additionally, the combined stress treatments significantly reduced the proline content and catalase activity, thereby affecting the antioxidant response of rice. Root low-temperature stress affects rice more than canopy low-temperature stress does, and drought stress exacerbates the negative effects of other stresses on rice. Overall, root low-temperature and combined stress treatments affect the antioxidant response, thereby influencing leaf stomatal conductance, photosynthetic traits, and ultimately affecting the yield, quality, and biomass of rice. Among the two varieties, Yuejingsimiao 2 showed stronger stress resistance than Huahang 31 did. Our study provides a reference for subsequent studies on the physiology of rice under adverse stress conditions.