【作者】 刘全吉；

【导师】 胡承孝；

【作者基本信息】 华中农业大学 ， 植物营养学， 2008， 博士

【摘要】 砷是自然界中的一种元素,广泛存在于无机环境和有机物中。砷因自然作用或者人为活动而进入陆地以及水环境中。在我国的湖北、湖南、山西等地方一些土壤中因为煤炭燃烧以及金属冶炼等原因砷的含量较高,给粮食安全生产、人们生活和健康带来了威胁。冬小麦和油菜是我国广泛种植的大田作物,在砷污染地区有不同程度的种植。本文在总结了国内外砷对植物生物有效性研究的基础上,通过土壤培养和营养液培养试验相结合,以冬小麦和油菜两种作物为材料,应用生理生化研究法并结合砷的在线形态分离技术,深入研究了冬小麦和油菜两种作物对砷的不同反应。主要研究结果如下:1.研究了冬小麦、油菜生长及产量对砷污染的反应。结果表明:当砷浓度为30 mg/L以上时,冬小麦根系和茎叶停止生长,趋于死亡而油菜仍能生长。30 mg/L砷处理时,冬小麦茎叶和根系生物量较对照分别降低了66.7%和78.3%;而相同浓度处理下,油菜的茎叶和根系生物量较对照却分别降低了47.5%和27.8%,这说明油菜较小麦对砷有较高耐性。土培条件下,低浓度的砷促进小麦生长,高浓度的砷抑制小麦生长和产量。油菜对砷有较高的耐性,不同砷浓度处理没有显著影响油菜的生长和产量。两种作物的可食用部分砷含量都没有超过安全标准,可以食用。比较油菜和小麦两种作物对砷污染的不同反应以及砷的累积情况,可知在土壤砷浓度小于60 mg/kg时,油菜、小麦都适合种植;当土壤砷浓度为80—100 mg/kg时,适合种植油菜。2.研究了冬小麦、油菜光合作用特性对砷污染的反应。结果表明:较低的砷水平显著提高冬小麦、油菜叶片中叶绿素a、叶绿素b和类胡萝卜素的含量。不同砷处理显著降低了冬小麦叶片净光合速率(Pn)、气孔导度(Gs)、胞间二氧化碳浓度(Ci)和蒸腾速率(Tr),影响小麦光合作用的主要因子是气孔限制。不同的砷水平提高了油菜叶片的Pn、Gs、Ci和Tr,促进了油菜的光合作用。这可能是砷显著提高了叶片中叶绿素的含量,同时油菜对砷的吸收较少,砷的毒害作用小使叶片的光合作用能力升高。不同砷水平处理下,冬小麦、油菜光合作用的不同反应说明砷对二者光合作用的影响机理不同,具体原因需进一步研究。在不同的生育期,随着土壤中砷浓度的增加,冬小麦的光合作用在低砷浓度处理时增加,高砷处理时显著降低;而油菜光合作用受砷影响不显著,证明油菜较小麦对砷有更高耐性。3.研究了冬小麦、油菜养分吸收对砷污染的反应。结果表明:砷主要累积在冬小麦和油菜的根系,转移到地上部分的量比较少只有根系砷浓度的1%—5%。溶液培养中,砷促进了小麦茎叶中Ca、Mg的含量,降低了K和P的含量;而根系中Ca、Mg、K、P的含量逐渐降低。油菜茎叶中养分元素受砷的影响比较小,但是Ca、Mg含量有不同程度提高。砷不同程度影响小麦、油菜根系中Fe、Mn、Cu和Zn等含量。油菜吸收和转移养分元素到茎叶中的能力要强于小麦,尤其油菜将P、Fe元素从根系转移到茎叶的能力很强,这可能是油菜较小麦对砷有较高耐性的原因之一。两种作物根系中Fe和P是营养元素中最容易受到砷影响的两种元素。4.研究了砷污染下不同磷肥浓度对冬小麦、油菜生长的影响。结果表明:缺磷时,高砷处理对油菜的毒害程度要比小麦严重;施入适当的磷肥后,油菜表现出对砷污染有较高的耐性,生长和产量不容易受到影响,磷肥显著降低了砷对油菜毒害。砷污染下,小麦受磷的影响不大,磷肥的施用对降低砷对小麦的毒害有一定作用,但效果不十分明显。在200 mg/kg砷污染的土壤中,适当施用磷肥,对小麦和油菜的生长有利,但是过高的磷肥会加重砷对小麦的毒害。在砷高度污染的土壤中,更适合种植油菜。5.研究了冬小麦、油菜体内砷含量和形态的变化。结果表明:冬小麦能够积累较高浓度的砷在体内。相较于冬小麦,油菜吸收累积砷的浓度要比冬小麦低。进入植物体内的砷,主要存在于冬小麦和油菜的根系,转移到地上部分的砷含量很低,为根系砷浓度的0.2%—1.5%。砷主要以无机三价态和五价态存在于冬小麦和油菜的根系和叶片中,且三价态的砷含量高于五价态砷的含量。随着溶液中砷浓度的提高,三价态的砷含量显著提高,而五价态砷含量变化不大。6.研究了冬小麦、油菜酶系统和非酶系统对砷污染的反应。结果表明:砷胁迫下,两种作物通过酶系统(SOD、CAT和POD)和非酶系统(Vc、-SH、GSH和PCs)的反应抵抗或降低砷对作物体本身的伤害。小麦酶系统在其抵抗砷毒害过程中发挥的作用不明显,它主要是通过非酶系统的作用来降低砷对自身的毒害;而油菜在较低砷浓度处理(0—8 mg/L)时,酶系统和非酶系统均非常活跃,二者共同作用来抵抗砷的毒害;在8-16 mg/L砷处理时,油菜通过非酶系统的作用来实现对自身的保护。更多还原

【Abstract】 Arsenic is a toxic element widely encountered in the environment and in organisms. Arsenic can enter terrestrial and aquatic environments through both natural formation and anthropogenic activities.In some areas of Hubei,Shanxi,Yunnan,and Hunan provinces of China,soil arsenic concentrations is much higher compared with other provinces because of coal fuels and metal smelters.In China both winter wheat and rape live through the winter and they are the main crops in these areas.High arsenic concentrations in soil or water may lead to elevated concentrations of arsenic in the grains of these two crops or in straw and give high risk to human’s health.Based on the reviews of soil arsenic physical and chemical activities and arsenic bioavailability to plants,solution culture and soil culture experiments were conducted to investigate the different physiological responses between winter wheat and rape which are planted in arsenic polluted soil.The main results were as following:1.The effects of arsenic on the growth and yields of winter wheat and rape were investigated under arsenic stress.The results indicated that the growth of wheat shoots and roots stopped when solution arsenic was more than 30 mg/L but rape did not. Comparing with the control,the shoot and root biomass of wheat decreased by 66.7% and 78.3%,while those of rape decreased by 47.5%and 27.8%,respectively..It implied that rape has higher tolerance than wheat under arsenic stress.In soil culture experiments,wheat yields were elevated at low rates of arsenic addition（＜60 mg/kg） but reduced at high rates of As concentrations（80-100 mg/kg）;the growth of rape hadn’t showed significant responses to As addition.Phosphorus concentrations in wheat at jointing and ear sprouting stages increased with increasing soil As concentrations,and these increases were assumed to contribute a lot to enhanced growth of wheat at low As treatments.Arsenic did not significantly affect phosphorus concentrations in rape either.The highest arsenic concentrations in wheat shoot and rape leaf was 8.31 and 3.63 mg/kg,respectively.Arsenic concentrations in wheat and rape grains did not exceed the maximum permissible limit for food stuffs of 1.0mg/kg.When soil arsenic concentration is 0-60 mg/kg,both wheat and rape can be grown satisfactorily without adverse effects;when soil arsenic concentration is 80-100 mg/kg,rape is more suitable to be planted than wheat.2.The effects of arsenic on photosynthesis of wheat and rape under arsenic stress were investigated.The results indicated that arsenic significantly increased the Chlorophyll（Chla,Chlb and Catotenoids） contents in winter wheat and rape’s leaves with solution arsenic increasing.However,Arsenic significantly decreased the photosynthetic rate（Pn）,stomatal conductance（Cs）,intercellular CO₂ concentration（Ci） and transpiration rate（Tr） of wheat under hydroponic conditions.Under arsenic stress, the stomatal limitation（Ls） of wheat leaf increased and Ci decreased.It suggested that the probable main factors to Pn decline were stomatal limitation.However,the Pn,Gs,Ci and Tr of rape leaves increased comparing with the control under hydroponic conditions. Because of the increasing chlorophyll and high tolerance to arsenic,rape’s photosynthesis increased and enhanced the growth of rape biomass.Soil culture experiments indicated that wheat’s Pn,Gs,Ci and Tr were affected by arsenic easily. They increased when soil arsenic concentration increased from 20 to 60 mg/kg but decreased under high soil arsenic treatments at different growth stages.But the photosynthesis of rape were not significantly affected by soil arsenic.It probably indicated that rape had high tolerance than wheat under arsenic stress.3.The effects of arsenic on the nutrients uptake of wheat and rape were investigated. The results indicated that the most of the arsenic accumulated in the roots of wheat and rape,and the shoot arsenic concentrations were much lower than those in roots.Arsenic increased Ca and Mg concentrations but decreased K and P concentrations in wheat shoots.The concentrations of Ca,Mg,K,P in wheat roots decreased with solution arsenic increasing.However,the nutrient elements of rape shoots were not significantly affected by arsenic.Under arsenic stress,rape has higher ability to transport nutrient elements from roots to leaves than wheat,especially for P and Fe transportation.Maybe this was one of the reasons that rape has higher tolerance to arsenic than wheat.4.The effects of phosphorus on the growth and yields of wheat and rape under arsenic stress were investigated.The toxicity of high soil arsenic concentrations to rape was more serious than wheat when soil P concentration was much lower.However,rape had high tolerance to arsenic than wheat and the growth and yield were not significantly affected by arsenic when 0.2 g/kg and 0.4 g/kg P fertilizers were added to this arsenic polluted soil.But the effects of P fertilizer on the toxicity of arsenic to wheat were not significant.Both arsenic concentrations in wheat and rape grains did not exceed the maximum permissible limit for food stuffs of 1.0mg/kg.When soil arsenic concentrations is very high（200mg/kg）,P fertilizer could decrease the toxicity of arsenic to wheat and rape.Rape is more suitable to be planted in arsenic polluted areas compared with wheat.5.Concentrations and speciation of arsenic in wheat and rape tissues were investigated.The results indicated that wheat tissues could accumulate more arsenic than rape tissues could.Most arsenic accumulated in wheat and rape roots.Arsenic in roots and shoots of both two crops occurred as As³⁺ and As⁵⁺ species and As³⁺ was the main species.As solution culture As increased,As³⁺ concentration significantly increased but As⁵⁺ did not.6.The responses of non-enzymatic antioxidant and enzymatic antioxidant systems of wheat and rape tissues were investigated.The results indicated that both wheat and rape had high tolerance to arsenic.For rape,the contents of non-enzymatic antioxidants （glutathione-GSH,total acid-soluble thiol-SH,and phytochelatins-PCs） followed similar trends as root As concentrations,which is increasing with solution arsenic concentrations. The activities of enzymatic antioxidants（superoxide dismatase-SOD,catalase-CAT, peroxidase-POD） in rape increases with As concentrations up to 4 mg/L and then decreased.The results indicate that rape has a strong tolerance to arsenic.Enzymatic antioxidants are more important at low As exposure,whereas the non-enzymatic antioxidants are more critical at high As exposure.For wheat,the function of enzymatic antioxidant system’s activities decreased and were not main system to decrease arsenic toxicity to this plant.But non-enzymatic antioxidants played an important role to decreased arsenic toxicity to wheat.更多还原