Aerenchyma Development and Irrigation Practices Shape Methane Emissions and Yield in Rice Paddies

  Rice root aerenchyma (RA) and irrigation practices play critical roles in key physiological processes in rice paddies, influencing both grain yield and methane (CH₄) emissions. However, the interaction between RA and irrigation practices, as well as its implications for CH₄ mitigation, remains poorly understood, complicating efforts to identify rice cultivars suited for reducing CH₄ emissions. To address this, we conducted field and pot experiments to investigate how RA impacts rice yield and CH₄ emissions under two common irrigation methods: continuous flooding (CF) and alternate wetting and drying (AWD). Our findings reveal that the interaction between RA and irrigation regime significantly affects both yield and CH₄ emissions. Under CF, cultivars with enhanced RA formation exhibited higher yields and lower CH₄ emissions, likely due to increased root oxygen loss, which promotes CH₄ oxidation and enhances nitrogen availability for plant growth. In contrast, under AWD, no significant differences in yield, methanogenesis, or methanotrophy were observed among cultivars with varying RA development. However, cultivars with well-developed RA increased CH₄ emissions by 28%–32% compared to those with less-developed RA, likely due to enhanced CH₄ transport from anaerobic soil layers to the atmosphere. Consistent with these observations, inhibiting RA development through root irrigation with brassinosteroids reduced CH₄ emissions under AWD conditions. In summary, our study demonstrates that AWD can reverse the effects of RA on CH₄ emissions, emphasizing the importance of integrating irrigation practices into CH₄ mitigation strategies and accounting for cultivar-specific variations.