Combined effects of climate stressors and soil arsenic contamination on metabolic profiles and productivity of rice (Oryza sativa L.).

Rice productivity and quality are increasingly at risk in arsenic (As) affected areas, challenge that is expected to worsen under changing climatic conditions. Free-Air Concentration Enrichment experiments revealed that eCO₂, eO₃, and eTemp, whether acting individually or in combination with low and high As irrigation, significantly impact rice yield and grain quality. Elevated CO₂ significantly increased shoot biomass, with minimal impact on root biomass, except under low As irrigation conditions. In contrast, eTemp alone reduced both shoot and root biomass, though the effect was not significant; eO₃ alone had little to no effect. Combined climatic stressors showed slight positive effects on growth. Under low As irrigation, eCO₂ and eO₃ promoted root growth but reduced shoot growth, while eTemp significantly suppressed both. High As irrigation exacerbated yield reductions, with the most severe decline observed under eTemp (66 %), followed by eCO₂ (48 %), eO₃ (36 %), and their combination (35 %). Arsenic irrigation, whether low or high, reduced macro and micronutrient concentrations in rice grains, with calcium being sole exception, remaining stable or even increasing. Sugar metabolites decreased under eCO₂, eO₃, and eTemp, but increased with As irrigation. Interestingly, climatic variables generally reduced grain As levels, high As irrigation combined with eCO₂ exposure resulted in elevated grain As. This poses a dual concern: increased cancer risk due to As but potential benefit for individuals with diabetes, as the higher amylose content contributes to lower glycemic index. However, rice grown under high As irrigation exhibited significant nutritional imbalances, being rich in maltose and amylose but deficient in organic acids, phytosterols, fatty acids, organosilicons, and carboxylic acids. These findings underscore the dual threat of climate change and As contamination to rice productivity and quality. Developing resilient rice varieties with low grain As content is essential to ensure sustainable agricultural production and nutritional security in As affected regions.