科學(xué)家發(fā)現(xiàn),，淹水種植的水稻比旱作種植法積累了更多的砷，這意味著可以采用一種可行的方法來(lái)防止這種有毒元素進(jìn)入食物鏈,。
砷中毒可以導(dǎo)致癌癥或者其它疾病，它在全世界范圍都是重大公共衛(wèi)生問(wèn)題,，在印度和孟加拉國(guó)尤其嚴(yán)重。在這些國(guó)家,，砷化物存在于地下水中，在淹水稻田中被水稻吸收,。
在發(fā)表于8月1日出版的《環(huán)境科學(xué)與技術(shù)》的一篇論文中，英國(guó)洛桑研究所的趙方杰及其同事比較了淹水種植的水稻與旱作種植的水稻之間的砷水平,，淹水種植水稻是南方國(guó)家最傳統(tǒng)的耕作方法,，而旱作種植水稻則指的是不把水稻根部浸于水中的做法。
這組科學(xué)家發(fā)現(xiàn),，同一個(gè)品種的水稻在淹水種植狀態(tài)下，稻秧和谷粒中的砷含量是旱作種植的10-15倍,。
這組作者說(shuō),，土壤被水淹沒(méi)導(dǎo)致砷在泥土溶液中迅速被激活,，并被水稻根系吸收并最終被水稻的谷粒吸收。他們指出,，一種原本開(kāi)發(fā)出來(lái)節(jié)約稀缺水資源的旱作種植水稻的方法,，可能為生產(chǎn)受到砷污染更少的稻米帶來(lái)額外的收益,。
趙方杰對(duì)本網(wǎng)絡(luò)記者表示：“在大田狀況下，旱作種植產(chǎn)量可能會(huì)低一些,，因?yàn)檠退畮椭刂仆寥谰€蟲(chóng)和病原體,。然而,，新的旱作品種已經(jīng)被開(kāi)發(fā)出來(lái)，它們可能具有很好的產(chǎn)量潛力,。”
他補(bǔ)充說(shuō),，在實(shí)驗(yàn)條件下，旱作種植的水稻的鋅,、銅,、錳和鎂等營(yíng)養(yǎng)元素濃度都比淹水種植要高,，意味著旱作水稻可能更有營(yíng)養(yǎng),。
中科院生態(tài)環(huán)境研究中心副研究員黃益宗認(rèn)為這些研究結(jié)果令人鼓舞,。但是他還說(shuō)，這組科學(xué)家應(yīng)該在更多水稻品種上進(jìn)行試驗(yàn),，表明水淹狀態(tài)下更高的砷獲取并非局限于某些特定品種,。
趙方杰還與日本岡山大學(xué)生物資源研究所的馬建鋒合著了一項(xiàng)水稻砷獲取機(jī)制方面的研究,， 上個(gè)月（7月22日）發(fā)表于《美國(guó)科學(xué)院學(xué)報(bào)》,。這項(xiàng)研究發(fā)現(xiàn)了兩種主要的把亞砷酸鹽從水中運(yùn)輸?shù)侥举|(zhì)部的植物蛋白質(zhì)。亞砷酸鹽是稻田土壤中砷的主要存在形式,，而木質(zhì)部把營(yíng)養(yǎng)從根部運(yùn)輸?shù)街仓?。這兩種硅運(yùn)輸?shù)鞍锥荚诟勘磉_(dá),，其中一種稱(chēng)為L(zhǎng)si1的蛋白是亞砷酸鹽進(jìn)入水稻的門(mén)戶(hù),，而另一種稱(chēng)為L(zhǎng)si2的蛋白控制著從根部到莖再到谷粒的流動(dòng),。
這組研究者還發(fā)現(xiàn)硅酸—含有硅,、氫和氧—會(huì)干擾亞砷酸鹽的攝取。他們提出,，增加土壤中可利用的硅,，可能會(huì)減少?gòu)耐寥篮凸喔扔盟剿镜纳榈倪\(yùn)輸。（生物谷Bioon.com）
生物谷推薦原始出處：
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.
