叶面喷施苹果酸对水稻Cd积累特性的影响

为了探讨水稻开花期喷施苹果酸对稻米Cd积累特性的影响，对4个早稻品种各器官的Cd含量及其Ca、Fe、Mn、Zn和氨基酸含量的变化进行了分析。结果表明，喷施2~3次5 mmol·L^-1苹果酸能使稻米、穗颈、穗节和旗叶中的Cd含量显著下降，稻米中的Cd平均含量从0.26 mg·kg^-1分别下降至0.14 mg·kg^-1和0.09 mg·kg^-1，降幅分别为46.15%和65.38%。喷施3次苹果酸后，稻米中的甘氨酸和缬氨酸含量分别增加了46.45%和34.56%。穗节中的Cd含量是穗颈和旗叶Cd含量的2~10倍，喷施2~3次苹果酸显著抑制了Cd从旗叶向穗节的转移，使穗节中的Cd浓度分别下降35.00%和56.88%。与此同时，喷施苹果酸使水稻各器官中Ca的含量显著上升，Fe、Mn、Zn的含量显著下降；其中稻米中的Ca含量增加16.02%~26.60%，Fe含量下降30.54%~43.14%，Mn含量下降23.07%~28.55%，Zn含量下降11.31%~19.57%。由此可见，喷施苹果酸主要通过抑制Cd由营养器官向籽粒的转运来降低稻米中的Cd含量，同时还能促进Ca的转运和稻米中氨基酸的合成。

Effects of foliar application with malic acid on the accumulation of cadmium in rice

To explore the effect of spraying malic acid on the characteristics of Cd accumulation in rice during the grain filling period, the content of Cd, Ca, Fe, Mn, Zn, and amino acids in the organs of four early rice varieties was analyzed. Experimental results showed that the application of 5 mmol·L^-1 malic acid significantly reduced the Cd content in grain, panicle neck, node, and flag leaf 2~3 times. The average Cd content in the four varieties of grains decreased from 0.26 mg·kg^-1 to 0.14 mg·kg^-1 and 0.09 mg·kg^-1, and the corresponding percentages of Cd decrease were 46.15% and 65.38%, respectively. After three applications of malic acid, the glycine and valine content in the grains increased by 46.45% and 34.56%, respectively. The Cd content in the nodes was approximately 2~10 times higher than that in the panicle necks and flag leaves. The application of malic acid significantly inhibited the transfer of Cd from flag leaves to nodes 2~3 times, which reduced the Cd content in the nodes by 35.00%~56.88%. At the same time, the application of malic acid significantly increased the Ca content but reduced the content of Fe, Mn, and Zn in the rice organs. The Ca content in grains increased by 16.02%~26.60%, whereas those of Fe, Mn, and Zn decreased by 30.54%~43.14%, 23.07%~28.55%, and 11.31%~19.57%, respectively. These results indicate that the application of malic acid significantly decreases Cd content in grains, by inhibiting the transport of Cd from the vegetative organs to the grains and promoting the transport of Ca and the synthesis of amino acids in rice grains simultaneously.