叶面喷施硫对镉污染土壤中水稻累积镉的机制研究

Cd（镉）污染稻田已成为影响全球农田土壤环境安全的重要问题，叶面喷施技术可以提高水稻对Cd的抗性，减少其对Cd的累积，保证农产品质量安全、维护土壤生态功能、防范环境和人体健康风险.通过两年四季的湖南省长沙县田间试验，探索叶面喷施S（以Na₂S计）在中轻度Cd污染稻田中的降镉、增产效果及其可推广性，进而设计水培试验，探究相关机制.结果表明:田间试验中，叶面喷施S可以将水稻产量提高6%~30%，水稻籽粒w（Cd）降低28%~50%.叶面喷施S能够增加水稻叶片的捕光能力和电子传递速率，与对照组相比，净光合速率提高2%~25%、气孔导度提高7%~25%、胞间CO₂浓度提高2%~10%、蒸腾速率提高1%~11%；实际光化学效率提升3%~21%，也可在一定程度上减缓光合系统结构和功能受到的损伤，同时提高光合作用碳同化的效率，提高水稻产量.傅里叶变换红外光谱图显示，叶面喷施S通过增强有机大分子类物质（如有机酸、多肽类等）的生成，可能直接与Cd发生螯合，区隔在细胞壁或者液泡上，降低Cd的侵害.研究显示，叶面喷施S在Cd胁迫水稻中积极参与生化过程的特定光合作用和蛋白质合成的调节，减轻了水稻Cd胁迫，可以尝试在同类型重金属污染农田土壤中推广. 

Protective Effect of Foliar Application of Sulfur on Rice under the Stress of Cd

Cadmium (Cd)-contaminated paddy soil has become a global agricultural safety issue. Paddy soils contaminated by Cd jeopardize the rice cultivation and the health of people with rice as their staple food. Foliage application to alleviate Cd toxicity in rice might offer a cost-effective and practical strategy for safe food production. Field experiments in two consecutive rice seasons and hydroponic experiment were performed to investigate the effectiveness and mechanisms of foliage dressing. Foliar spray of S was effective to reduce the Cd concentration in rice grain (28%-50%) and increase the grain yield (6%-30%). The reduction of Cd concentration in rice decreased the direct damage to the photosynthetic system (with the net photosynthetic rate increased to 2%-25%; stomatal conductance increased to 7%-25%; intercellular CO₂ concentration increased to 2%-10%; transpiration rate increased to 1%-11%; and actual PSⅡ photochemical efficiency increased to 3%-21%), and then increased the rice growth. Fourier transform infrared spectra showed that the foliar treatment stimulated the syntheses of aliphatic acid, polysaccharides, carboxylate and proteins, which likely reduced mobility of Cd in cell wall or vacuole. This study provided preliminary evidence that the effect of foliar application of S likely retained the structure of plant cells and effectively regulated protein expression by alleviating Cd stress without sacrificing yield, which has great potential for the remediation of vast agricultural fields.