Ye Wenling, Zhang Jingjing, Fan Ting, Lu Hongjuan, Chen Haiyan, Li Xuede, Hua Rimao
School of Resources and Environment, Anhui Agricultural University, Hefei, Anhui 230036, China; Hefei Scientific Observing and Experimental Station of Agro-Environment, Ministry of Agriculture, P.R. China.
School of Resources and Environment, Anhui Agricultural University, Hefei, Anhui 230036, China.
Ecotoxicol Environ Saf. 2017 Sep;143:87-91. doi: 10.1016/j.ecoenv.2017.05.006. Epub 2017 May 12.
Arsenic (As) speciation in the phloem sap of rice plants and its role in As accumulation in rice grains remain largely uncharacterized. In the present study, we tested As chemical species in the phloem exudates of rice treated with arsenate [As(V)], arsenite [As(III)], monomethylarsonic acid [MMA(V)], or dimethylarsinic acid [DMA(V)]. As(V) was the main species (58%) in the phloem exudates of As(V)-exposed rice, whereas As(III) predominated (69%) in As(III)-exposed rice. A large proportion of As(V) (41-45%) was observed in the phloem exudates when rice was treated with methylated As species. High concentrations of phytochelatins were detected in the phloem exudates when the As(V) treatment level was increased. The role of phloem transport was analyzed by applying a ±stem-girdling treatment to the rice plants, limiting phloem transport to the grain in rice pulsed with As(III), As(V), MMA(V), or DMA(V). The findings of the present study indicate that organic As is more mobile than inorganic As during phloem transport. Phloem transport accounted for 54% of As(III), 56% of As(V), 100% of MMA(V), and 89% of DMA(V) transport to the grain. The total As concentration and As(III) percentage in rice phloem and grain were significantly affected by increasing the phosphate concentration in the medium.
水稻植株韧皮部汁液中的砷（As）形态及其在水稻籽粒中砷积累的作用在很大程度上仍未明确。在本研究中，我们检测了用砷酸盐[As(V)]、亚砷酸盐[As(III)]、一甲基胂酸[MMA(V)]或二甲基胂酸[DMA(V)]处理的水稻韧皮部渗出液中的砷化学形态。在暴露于As(V)的水稻韧皮部渗出液中，As(V)是主要形态（58%），而在暴露于As(III)的水稻中，As(III)占主导（69%）。当水稻用甲基化砷形态处理时，在韧皮部渗出液中观察到很大比例的As(V)（41 - 45%）。当As(V)处理水平增加时，在韧皮部渗出液中检测到高浓度的植物螯合肽。通过对水稻植株进行±茎环割处理来分析韧皮部运输的作用，限制用As(III)、As(V)、MMA(V)或DMA(V)脉冲处理的水稻中韧皮部向籽粒的运输。本研究结果表明，在韧皮部运输过程中，有机砷比无机砷更具移动性。韧皮部运输分别占向籽粒运输的As(III)的54%、As(V)的56%、MMA(V)的100%和DMA(V)的89%。通过增加培养基中的磷酸盐浓度，显著影响了水稻韧皮部和籽粒中的总砷浓度以及As(III)百分比。
