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重金属在土壤中不易随水淋滤,且不能被土壤微生物分解,同时具有生物放大和富集效应,因此严重威胁着我们的农田生态系统和食品安全[1-2].如镉元素进入人体后可损害血管导致组织缺血引起多系统损伤[3].同种植物不同器官,不同生长阶段对汞、镉的吸收积累和分布,都具有一定的变化规律.通常镉、汞进入植物细胞后,会与细胞内的谷胱甘肽(GSH)、植物络合素(PCs)、金属硫蛋白等发生络合,以络合物形式运往液泡内储存起来,从而使细胞液中游离Cd2+,Hg2+的浓度降低,减轻毒害作用[4-6].因此叶片中高质量浓度GSH或PCs很可能有助于叶肉细胞对镉、汞离子的络合和固定,减少其向水稻籽粒中的运输.硒是一种人和动物必需的微量元素,每日适量的硒摄入,可以延缓衰老,增强免疫力,降低心血管疾病和癌症的发生率[7].在植物体内硒对GSH系统具有增强作用,且能够影响植物螯合肽(PCs)的合成[8-9],近些年关于硒对重金属的拮抗作用是研究热点. Zhang等[10]报道,在贵州万山汞矿附近随着土壤中硒的质量分数的升高,稻米中硒质量分数上升,土壤中的IHg和MeHg向稻米中的转运率降低. Hu等[11]研究表明,在土壤中施用0.5 mg/kg亚硒酸钠,糙米中的硒的质量分数增加,籽粒中镉的累积量下降了44.4%.张海英等[12]发现,草莓喷施2.5~5.0 mg/L适宜质量浓度亚硒酸钠能够有效抑制草莓叶片和果实对重金属镉和铅的吸收.叶面施硒是提高水稻籽粒硒的质量分数非常重要的途径[13],通过叶面喷施亚硒酸钠抑制水稻吸收和转运重金属的研究还未见报道.本研究通过给水稻喷施不同质量浓度亚硒酸钠,研究喷施亚硒酸钠对水稻吸收和转运镉、汞的影响,以期为大米安全生产提供一定的技术及理论支撑.
Effects of Foliar Application of Selenium on Cadmium and Mercury Absorption in Different Growth Periods of Rice
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摘要: 试验通过水稻叶面喷施不同质量浓度亚硒酸钠(0.2,1.5,5.0 mg/L),研究亚硒酸钠对水稻体内镉、汞积累和转运的影响.结果表明,叶面喷施亚硒酸钠(<1 mg/L)能够明显提高籽粒中的硒的质量分数,对水稻各生育期各部位镉的质量分数以及迁移无影响,却能够明显降低成熟期籽粒汞的质量分数和次级迁移系数(STI).喷施质量浓度过高(5 mg/L)会促进孕穗期、成熟期镉向茎叶和籽粒中的迁移,从而使茎叶和籽粒中镉的质量分数增加,但是对水稻各部位的汞的质量分数和迁移无影响.因此孕穗期和成熟期是硒影响水稻体内镉、汞积累的关键时期,喷施亚硒酸钠对水稻吸收和转运重金属的影响结果与喷施质量浓度以及金属阳离子的特性有关.Abstract: Sodium selenite at 0.2, 1.5 or 5.0 mg/L was foliar sprayed onto rice to study its effects on the accumulation and transport of cadmium and mercury in the plants. The results showed that sodium selenite spraying at < 1 mg/L significantly increased selenium content in the grains, reduced the mercury content in the seed and the secondary transport index of mercury in the rice plant, but it had no effect on the cadmium content in the seed and the transport of cadmium in rice plants. Sodium selenite spraying at a high concentration (5 mg/L) promoted the transport of cadmium, and thus increased the cadmium content in the shoot and the grain, but it had no effect on mercury content in rice and migration of mercury in rice plant. So the booting stage and the maturing stage are the critical period for selenium to influence the accumulation and transport of cadmium and mercury, and the results are different between different metal cations.
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Key words:
- rice /
- selenium /
- heavy metal .
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表 1 土壤基本理化性质
土壤类型 pH 有机质/
(g·kg-1)碱解氮/
(mg·kg-1)速效磷/
(mg·kg-1)速效钾/
(mg·kg-1)全汞/
(mg·kg-1)全硒/
(mg·kg-1)水稻土 6.6 18.73 112.31 12.76 79.60 0.053 0.235 表 2 不同生育期水稻各部位生物量(g/盆,干质量)
处理 拔节期 孕穗期 成熟期 Cd/
(mg·kg-1)Hg/
(mg·kg-1)Se/
(mg·L-1)根 茎叶 根 茎叶 穗 根 茎叶 籽粒 1.5 0 0 1.76a 3.05a 7.84a 17.75a 4.89a 9.84a 18.99a 14.18a 0.2 1.62a 3.13a 7.92a 17.97a 4.99a 9.96a 19.21a 14.46a 1 1.71a 3.02a 7.86a 17.63a 4.87a 9.87a 19.13a 15.25a 5 1.72a 2.93a 7.79a 18.05a 4.94a 9.97a 18.99a 14.20a 0 2 0 1.68a 2.96a 8.04a 17.90a 5.04a 9.78a 19.19a 15.16a 0.2 1.66a 3.20a 8.01a 17.96a 4.81a 9.93a 18.88a 14.74a 1 1.59a 2.89a 8.08a 17.84a 5.03a 9.91a 19.13a 14.81a 5 1.63a 3.06a 7.93a 17.94a 4.91a 9.89a 19.52a 14.35a 注:表中数据为平均值±SD,同一列栏中不同小写字母表示数据差异具有统计学意义(p<0.05,Duncan);下同. 表 3 籽粒中的硒、镉、汞质量分数
处理
Se/(mg·L-1)籽粒 籽粒 Se/(mg·kg-1) Cd/(mg·kg-1) Se/(mg·kg-1) Hg/(mg·kg-1) 0.0 0.025d 0.233 b 0.017d 0.493a 0.2 0.283c 0.191b 0.306c 0.373b 1.0 0.349b 0.238b 0.412b 0.369b 5.0 0.530a 0.385a 0.485a 0.446a 表 4 各生育期水稻汞、镉转移率和叶片丙二醛(MDA)浓度
处理 拔节期 孕穗期 成熟期 Se/
(mg·L-1)Cd/
(mg·kg-1)Hg/
(mg·kg-1)MDA/
(μmol·L-1)PTI MDA/
(μmol·L-1)PTI STI MDA/
(μmol·L-1)PTI STI 0 1.5 0 0.487a 0.602a 0.923b 0.691b 0.153a 0.953a 0.738b 0.230b 0.2 1.5 0 0.550a 0.582a 0.740cd 0.609b 0.165a 0.863a 0.671b 0.197b 1 1.5 0 0.423a 0.482a 0.847bc 0.695b 0.137ab 0.803a 0.724b 0.231b 5 1.5 0 0.457a 0.513a 1.097a 0.957a 0.177a 0.817a 0.908a 0.283a 0 0 2.0 0.493a 0.450b 0.857b 0.578b 0.139b 0.817a 0.714b 0.323a 0.2 0 2.0 0.528a 0.465b 0.766c 0.653b 0.119b 0.780a 0.806b 0.233b 1 0 2.0 0.443a 0.458b 0.732d 0.667b 0.098b 0.793a 0.719b 0.257ab 5 0 2.0 0.547a 0.444b 0.983a 0.514b 0.139b 0.819a 0.748b 0.281a -
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