Effects And Mechanism Of Selenium On Arsenic Uptake In Upland Rice Under Different Water Conditions

The soil pollution of As is serious in China.As pollution in farmland has posed a serious threat to the safe production of rice in the rice growing area of middle and southwest China.In the experiment,arsenic high（V2）and low（V1）absorption upland rice cultivar selected under the condition of wetting irrigation were chosen as experimental materials,and selected typical As pollution(61.24 mg·kg^-1)soil.We studied under different water conditions（wetting irrigation,conventional irrigation,flooded irrigation）,the effects of selenium（Se）with different forms（Na₂SeO₃,Na₂SeO₄）under different concentrations of root application(0,1.0,5.0 mg·kg^-1)and leaf application(0,1.0,5.0 mg·L^-1)on growth,absorption and transport of arsenic,photosynthesis and antioxidant system in upland rice.The main results are listed below.（1）The effects of selenium on absorption,transport and distribution of arsenic in upland rice under different water conditions were studied.Compared with conventional irrigation and flooded irrigation,wetting irrigation significantly inhibited the growth and yield of upland rice,and the accumulation of As in upland rice,increased root to leaf,root to stem transfer coefficient and stem to leaf,stem to brown rice,leaf to brown rice partition coefficient.Compared with flooded irrigation,under wetting irrigation,the partition coefficient of stem to brown rice and leaf to brown rice increased by 406.6-434.7%and16.7-28.3%for V1,and increased by 251.6-310.6%and 228.5-272.1%for V2.And compared with conventional irrigation,under wetting irrigation,the partition coefficient of stem to brown rice and leaf to brown rice of the upland rice varieties V1 and V2 increased by 467.0-535.4%,416.6-550.2%and6.7-28.3%,66.6-100.0%,respectively.Sodium selenite of root application promoted the growth of upland rice,inhibited the absorption of As in upland rice shoots,inhibited the transport of As from root to shoot,increased the stem to leaf partition coefficient,and decreased the partition coefficient of brown rice to leaf and brown rice to stem.（2）The effects of selenium on absorption and antioxidant system of arsenic in upland rice under different water conditions were studied.Compared with wetting irrigation,flooded irrigation significantly promoted the growth of rice seedling,the above-ground fresh weight and plant height of the upland rice varieties V1 and V2 increased by 218.1-302.6%,95.7-188.5%,and 11.5-14.5%,11.5-16.8%,respectively.The content of As in roots,stems and leaves under wetting irrigation is much less than that of flooded irrigation.The content of As in different parts upland rice varieties V1 is lower than that of V2 under wetting irrigation,and the result was opposite under flooded irrigation.Under flooded irrigation,the transfer coefficient of root to leaf and root to of the upland rice varieties V1 and V2 decreased by 59.5-90.5%,77.4-82.4%and 13.6-78.9%,55.2-91.0%,respectively,and the content of MDA was also decreased.Selenium of root application alleviated arsenic pollution stress and inhibited the absorption of As in upland rice shoots.Compared with CK,with four different levels of selenium（Se⁴1.0,Se⁴5.0,Se⁶1.0,Se⁶5.0）,the above-ground fresh weight of the varieties V1 and V2 increased by19.2-57.2%,6.7-25.3%and 18.6-37.0%,14.5-28.4%,the content of As in stem of the varieties V1 and V2 decreased by 3.9-22.5%,31.8-46.4%and 13.7-34.7%,9.8-47.7%,and the content of As in leaf of the varieties V1 and V2 decreased by 3.1-19.2%,18.5-45.5%and 25.5-39.7%,21.4-38.7%under wetting irrigation and flooded irrigation.Se inhibited the transport of As from root to shoot of upland rice.The application of Se decreased the content of MDA,and the activity of antioxidant enzymes,such as SOD,POD and CAT,was improved.（3）The effects of selenium of leaf application on absorption of arsenic and photosynthesis in upland rice under different water conditions were studied.Wetting irrigation inhibited photosynthesis in upland rice,and Pn,Gs,Ci,Tr of varieties V1 and V2 decreased by 11.4-42.5%,18.4-41.3%,3.5-13.5%,26.5-42.4%and 8.0-22.0%,27.0-42.8%,7.7-9.4%,34.0-45.1%,respectively,compared with flooded irrigation.Selenium of leaf application alleviated adversity stress and inhibited absorption of arsenic in upland rice.Compared with CK,under four different levels of selenium（Se⁴1.0,Se⁴5.0,Se⁶1.0,Se⁶5.0）,the content of As in stem of the varieties V1 and V2 decreased by 9.0-28.9%,6.0-39.0%and 4.5-36.0%,47.0-65.0%,and the content of As in leaf of the varieties V1 and V2 decreased by 1.6-21.3%,13.2-35.0%and 9.7-26.7%,19.3-44.0%under wetting irrigation and flooded irrigation,what’s more,the application of Se promoted photosynthesis in upland rice,and Pn of the varieties V1 and V2 increased by 9.5-36.1%,13.1-38.9%and 11.1-21.5%,7.5-27.0%.