不同水稻品種根部鐵膜生成之差異及其對水稻吸收砷之影響

Abstract

本研究以水耕法探討不同水稻品種間鐵膜形成之差異；並自秈稻、稉稻中分別篩選出鐵膜多與寡的兩個品種於含砷養液栽培，以了解溶液中砷與鐵對水稻根表面鐵膜形成之交互作用，進一步探討不同鐵膜生成量對水稻吸收砷之影響。結果顯示，養液於100 mg Fe(II) L-1濃度下，水稻根表面會生成紅棕色之鐵膜，且生成量隨品種不同而有所差異。其中台稉9號(稉稻)與台秈2號(秈稻)為鐵膜量較高之品種；桃園3號(稉稻)與中秈育962021號(秈稻)為鐵膜量較低之品種，並以此探討不同鐵膜量之水稻品種於不同砷濃度下生長之差異。結果發現，水稻根表面鐵膜量隨環境中砷濃度增加而增加，且隨著鐵膜量增加，鐵膜所吸持之磷與砷量也隨之增加。然而鐵膜之吸持能力因品種不同而有差異，推測可能為不同品種水稻根表面鐵膜生成之鐵(氫)氧化物不同所致，其中以台稉9號鐵膜之砷吸持能力最佳。植體分析結果顯示水稻根表面鐵膜之生成會阻礙水稻對磷之吸收，同時也阻擋對砷之吸收，又以台稉9號鐵膜阻擋之砷含量最多，可高達植體總吸持(收)砷含量的52-65%。整體而言，由於鐵膜可有效阻擋砷，因此於根表面形成鐵膜之水稻，砷較不易進入植體內，有助於降低人類因食用稻米而攝入砷之風險。

The formation of iron plaque in the different genotypes of rice seedlings grown in nutrient solutions was investigated. Two genotypes of rice seedlings with the highest and lowest capability of forming iron plaque were selected from tested Indica and Japonica rice respectively to further evaluate the effect of iron plaque on the arsenic uptake by rice seedlings. The results showed that red brown iron plaque coating on root surface of rice grown in nutrient solutions containing 100 mg Fe(II) L-1 was observed and the amounts of iron plaque formation significantly varied among the genotypes. TK 9 (Japonica) and TS 2 (Indica) had the highest amounts of iron plaques and TY 3 (Japonica) and TCSY 962021 (Indica) had the lowest amounts of iron plaques among all the tested genotypes. The results of effect of iron plaque on the arsenic uptake by rice seedling showed that increasing arsenic concentration in nutrient solutions increased the amounts of iron plaques and thus increased amounts of phosphorus and arsenic accumulated in iron plaques. The iron plaque of TK 9 had the highest sorption capability for arsenic among the four tested genotypes. The amounts of arsenic sorbed on iron plaques of TK9 were 52-65% of total arsenic uptake/sorption by the rice seedlings. The results suggest that iron plaque formation on the root surface is important on preventing arsenic uptake by rice and hence decreasing the risk of human beings exposing to arsenic through rice diet.