科学家发现，淹水种植的水稻比旱作种植法积累了更多的砷，这意味着可以采用一种可行的方法来防止这种有毒元素进入食物链。
砷中毒可以导致癌症或者其它疾病，它在全世界范围都是重大公共卫生问题，在印度和孟加拉国尤其严重。在这些国家，砷化物存在于地下水中，在淹水稻田中被水稻吸收。
在发表于8月1日出版的《环境科学与技术》的一篇论文中，英国洛桑研究所的赵方杰及其同事比较了淹水种植的水稻与旱作种植的水稻之间的砷水平，淹水种植水稻是南方国家最传统的耕作方法，而旱作种植水稻则指的是不把水稻根部浸于水中的做法。
这组科学家发现，同一个品种的水稻在淹水种植状态下，稻秧和谷粒中的砷含量是旱作种植的10-15倍。
这组作者说，土壤被水淹没导致砷在泥土溶液中迅速被激活，并被水稻根系吸收并最终被水稻的谷粒吸收。他们指出，一种原本开发出来节约稀缺水资源的旱作种植水稻的方法，可能为生产受到砷污染更少的稻米带来额外的收益。
赵方杰对本网络记者表示：“在大田状况下，旱作种植产量可能会低一些，因为淹水帮助控制土壤线虫和病原体。然而，新的旱作品种已经被开发出来，它们可能具有很好的产量潜力。”
他补充说，在实验条件下，旱作种植的水稻的锌、铜、锰和镁等营养元素浓度都比淹水种植要高，意味着旱作水稻可能更有营养。
中科院生态环境研究中心副研究员黄益宗认为这些研究结果令人鼓舞。但是他还说，这组科学家应该在更多水稻品种上进行试验，表明水淹状态下更高的砷获取并非局限于某些特定品种。
赵方杰还与日本冈山大学生物资源研究所的马建锋合著了一项水稻砷获取机制方面的研究， 上个月（7月22日）发表于《美国科学院学报》。这项研究发现了两种主要的把亚砷酸盐从水中运输到木质部的植物蛋白质。亚砷酸盐是稻田土壤中砷的主要存在形式，而木质部把营养从根部运输到植株。这两种硅运输蛋白都在根部表达，其中一种称为Lsi1的蛋白是亚砷酸盐进入水稻的门户，而另一种称为Lsi2的蛋白控制着从根部到茎再到谷粒的流动。
这组研究者还发现硅酸—含有硅、氢和氧—会干扰亚砷酸盐的摄取。他们提出，增加土壤中可利用的硅，可能会减少从土壤和灌溉用水到水稻的砷的运输。（生物谷Bioon.com）
生物谷推荐原始出处：
Environ. Sci. Technol., 42 (15), 5574–5579, 2008. 10.1021/es800324u
Growing Rice Aerobically Markedly Decreases Arsenic Accumulation
X. Y. Xu, S. P. McGrath, A. A. Meharg, and F. J. Zhao
Soil Science Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, U.K., School of Earth and Space Science, University of Science and Technology of China, Hefei, Anhui 230026, China, and School of Biological Sciences, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen, AB24 3UU, U.K.
Abstract:
Arsenic (As) exposure from consumption of rice can be substantial, particularly for the population on a subsistence rice diet in South Asia. Paddy rice has a much enhanced As accumulation compared with other cereal crops, and practical measures are urgently needed to decrease As transfer from soil to grain. We investigated the dynamics of As speciation in the soil solution under both flooded and aerobic conditions and compared As accumulation in rice shoot and grain in a greenhouse experiment. Flooding of soil led to a rapid mobilization of As, mainly as arsenite, in the soil solution. Arsenic concentrations in the soil solution were 7−16 and 4−13 times higher under the flooded than under the aerobic conditions in the control without As addition and in the +As treatments (10 mg As kg−1 as arsenite or arsenate), respectively. Arsenate was the main As species in the aerobic soil. Arsenic accumulation in rice shoots and grain was markedly increased under flooded conditions; grain As concentrations were 10−15-fold higher in flooded than in aerobically grown rice. With increasing total As concentrations in grain, the proportion of inorganic As decreased, while that of dimethylarsinic acid (DMA) increased. The concentration of inorganic As was 2.6−2.9 fold higher in the grain from the flooded treatment than in that from the aerobic treatment. The results demonstrate that a greatly increased bioavailability of As under the flooded conditions is the main reason for an enhanced As accumulation by flooded rice, and growing rice aerobically can dramatically decrease the As transfer from soil to grain.
