2种常规水稻Cd、Zn吸收与器官分配的生育期变化:品种、土壤和Cd处理的影响

Uptake and Partitioning of Cd and Zn by Two Non-hybrid Rice Cultivars in Different Growth Stages: Effect of Cultivars, Soil Type and Cd Spike

Cd在土壤-作物-膳食食物链中的迁移是人类对环境Cd暴露及其健康风险的主要途径,而水稻是子粒Cd积累最强的大宗作物之一.采用全生育期淹水盆栽试验研究了2种常规水稻(高Cd吸收品种“苏香粳1号”和低Cd吸收品种“99-22”)在添加Cd(2mg·kg-1)和不添加Cd处理下对2种土壤(红沙泥田,乌栅土)中Cd、Zn的吸收及其生育期变化.结果表明:1)常规水稻对Cd、Zn的吸收积累受土壤、品种和外源Cd的影响.Cd处理、土壤、品种间的正交互作用(高Cd吸收品种植于高Cd处理且Cd有效性高的红壤中)使常规稻植株Cd/Zn比成数十倍提高,从而使子粒Cd/Zn比产生强烈升高;2)水稻对Cd、Zn的吸收强度因不同生育期而异,Cd吸收的主要时期是分蘖期和成熟期,而Zn吸收的主要时期则是分蘖期、抽穗期和灌浆期.在整个生育期中,水稻Cd吸收伴随着对Zn的排斥现象,这在高Cd吸收下尤为强烈;3)水稻各器官对Cd、Zn的吸收分配无论是同品种的生育期间抑或同生育期时的不同品种间均有显著差异.Cd积累量为根系>穗粒>茎叶,而Zn却表现为茎叶>根系、穗粒.观察到水稻吸收的Cd在生育后期向穗粒的强烈运移.相对于低Cd吸收品种来说,Cd向穗粒转运较强,而Zn的转运较弱是高Cd吸收品种子粒Cd积累强而Cd/Zn比高的植株因素.

Soil-food crop-diet transfer has been considered as the dominant pathway of human exposure to Cd and the potential health risk. Rice （Oryza sativa L.）, in particular, has been concerned as a food crop that significantly accumulates Cd in grains. A pot experiment of Cd and Zn uptake and portioning in plant organs during the whole growing period was conducted using consistently submerged condition. Two cuhivars of non-hybrid rice, Suxiangjing 1 （high Cd affinity cuhivars） and 99-22 （low Cd affinity cuhivars）, were grown in two paddy soils with contrasting chemical properties and soil total Cd and Zn contents. Cd was spiked at 0mg·kg^-1 of soil （as the control） and 2mg·kg^-1, respectively. Rice plants were harvested in different growth stages and the biomass and Cd and Zn contents, of different organs were determined. The results obtained were as follows： 1） Uptake of Cd and Zn by the rice were affected by soil type, cultivars, and Cd spike, of which under a positive mutual interaction （high Cd affinity cuhivars on the soil of high Cd availability） very high grain Cd and Cd/Zn ratio was observed due to strong uptake and high grain partitioning of Cd; 2） Cd uptake and organ partitioning by rice plant varied with the different growing stages. Significant uptake of Cd was observed in the tillering and ripening stages while that of Zn was in tillering, spiking and filling stages; Zn depletion with enhanced Cd uptake was aparent in the whole life period, especially under spiked Cd treatments; 3） There existed significant differences in Cd and Zn partitioning in plant organs both between the growth stages of a single cuhivars and between the cuhivars in a single stage. Total Cd amount was in the order： roots 〉 grains 〉 shoots, and the total Zn was in an order： shoots 〉 roots and grains. An intense translocation of plant Cd to grains happened even the ripening stage of both cuhivars. Stronger Cd but weaker Zn transfer to grains by the high Cd affinity cuhivars than the low one could be considered as a major plant factor controlling high Cd uptake and accumulation, and the high Cd/Zn ratio in rice grains.