硒对不同水稻幼苗镉胁迫的缓解作用及其对矿质营养的影响

Alleviation role and effects of selenium on mineral nutrients in rice(Oryza sativa)seedlings under cadmium stress

采用水培试验,研究3μmol/L Se(亚硒酸钠)对杂交籼稻品种宜香2115(籽粒低Cd积累)和川谷优2348(籽粒高Cd积累)幼苗在不同浓度(0、0.1和1mmol/L)Cd胁迫下的缓解作用。结果表明:加Se显著增加了不同浓度Cd胁迫下2个水稻品种幼苗的生物量、叶绿素a含量,但川谷优2348叶绿素b含量下降;加Se可增加2个水稻品种体内抗氧化物质(抗坏血酸和谷胱甘肽)含量,且川谷优2348的2种抗氧化物质含量均高于宜香2115,表现出品种间差异;在1mmol/L Cd胁迫下,Se主要通过促进川谷优2348合成更多的抗坏血酸和谷胱甘肽来提高对Cd的耐受性,而宜香2115主要通过Se促进植物螯合肽的合成来降低Cd的毒害;加Se能使幼苗维持较高的根部活力,从而降低遭受Cd胁迫伤害的程度;随着Cd胁迫程度增加,2个水稻品种幼苗地上部Cd含量显著上升,加Se可直接抑制2个水稻品种对Cd的吸收;在Cd胁迫下,Se能降低2个水稻品种地上部Ca、Zn含量,但对Cu、Mn含量变化的影响存在品种间差异,而Se对2个水稻品种根部矿质元素含量影响表现一致,即在Cd胁迫下根部Ca、Cu含量增加,Mn、Zn含量减少。

Summary Substantial amounts of heavy metals including cadmium have been released to the environment by geological activities or by anthropogenic impacts and industrialization,such as mining,smelting activities,sewage sluge,and the unreasonable utility of fertilizers and pesticides.Cadmium （Cd） is a toxic heavy metal with high mobility and can be readily absorbed into rice plants and transported to human bodies through the food chain. Selenium （Se） is an essential element for animals and human beings, which usually acts as a co-factor in antioxidant enzymes in human bodies.Though Se is not considered as an essential element for plants,there are lots of evidence suggesting its beneficial effects for plant growth and resistance to heavy metal stress.However, little effort has been found about the comparative study of Se effects with respect to different grain Cd-accumulative rice seedlings.Therefore,the aim of the present study is to explore the mitigation mechanisms of Se to Cd stress in different rice cultivars. In this research,a hydroponic experiment was conducted to study the alleviation role of Se in two hybrid rice variety（Yixiang 2115 with low grain Cd accumulation,Chuanguyou 2348 with high grain Cd accumulation） seedlings.Cd in the concentrations of 0,0.1,1 mmol/L with or without 3μmol/L Se（Na2SeO3）solutions were treated on the two rice seedlings.The root and shoot biomasses,chlorophyll contents,Cd concentration and contents of mineral nutrient elements were measured. The results showed that,Se increased significantly the biomass and chlorophyll a content of the two rice seedlings under the Cd stress,but decreased the chlorophyll b content in Chuanguyou 2348,which had the high Cd content in grain.The contents of ascorbic acid and glutathione in the two rice seedlings also increased with the supplement of Se,but those were higher in Chuanguyou 2348 than in Yixiang 2115,showing the differences between the two varieties.Under the 1 mmol/L Cd stress,Se promoted the synthesis of ascorbic acid and reduced glutatione to alleviate Cd stress in Chuanguyou 2348,but accelerated the synthesis of phytochelatins in Yixiang 2 1 1 5 to mitigate Cd stress.Se also mitigated the inj uries of the Cd stress to roots,which kept root activity in higher level than those without Se supplementation.The Cd content in shoots of the two varieties increased sharply with the Cd concentration increasing in the nutrient solution.Se could inhibit the absorption of Cd in the two varieties directly.Se could decrease the contents of calcium（Ca）and zinc（Zn）in shoots of the two varieties under the Cd stresses,but induced different reactions on cuprum（Cu）and manganese（Mn）contents.To the roots,Se increased the Ca and Cu contents,but decreased the Zn and Mn contents in the two varieties under the Cd stress conditions. It is concluded that,Se can mitigate inhibition of Cd stress to rice seedling growth by elevating seedling biomass,chlorophyll a content,changing the contents of ascorbic acid,glutathione and non-protein thiols, keeping higher root activity compared with only Cd treatment.Besides,Se can directly suppress Cd uptake in rice seedlings and mainly affects Cu and Mn concentrations in shoots between the two rice varieties.