Abstract
Rice, as one of the most important staple crops worldwide, relies heavily on its light energy utilization efficiency for yield formation. However, the regulatory mechanisms of the rhizosphere oxygen environment on rice photosynthesis and physiological metabolism remain poorly understood. In this study, three ecological rice types—tillering-stage rice, deepwater rice, and upland rice—were subjected to rhizosphere saturated dissolved oxygen (RSDO) treatment under hydroponic conditions, with natural conditions as the control, to systematically analyze changes in photosynthetic characteristics, chlorophyll fluorescence parameters, photosynthetic pigment content, and growth indicators. The results showed that RSDO significantly decreased maximum photochemical efficiency, actual photochemical efficiency, electron transport rate, and photochemical quenching coefficient, while increasing non-photochemical quenching and intercellular CO₂ concentration, indicating suppressed actual photochemical efficiency accompanied by enhanced non-photochemical energy dissipation. Moreover, chlorophyll a, chlorophyll b, and total chlorophyll contents decreased markedly, whereas carotenoid content and relative conductivity increased, reflecting inhibited pigment synthesis and reduced cell membrane stability. In terms of growth performance, shoot dry weight and leaf area index were significantly reduced in rice and deepwater rice, while upland rice exhibited stronger adaptability. Overall, these findings demonstrate that rhizosphere oxygen saturation at the tillering stage markedly suppresses light energy utilization and pigment biosynthesis in rice leaves, thereby hindering early plant growth, although upland rice maintains higher resilience. This study elucidates the influence of rhizosphere oxygen environment on rice photosynthetic and physiological responses, providing important theoretical insights for oxygen-nutrition cultivation strategies and breeding of low-oxygen-tolerant rice varieties.
