【正文】 t of these metals is further limited by the high cationexchange capacity of cell walls, unless the metal ion is transported as a noncationic metal chelate. The strong affinity for these cations to form plexes with sulphur interferes with normal enzymatic functions within humans. Numerous enzymes which function as metabolic regulators contain sulphur within ‘sulfhydryl’ groups, and it is these groups which attract, or are attracted to, the metal cations. This consequently alters the capacity of the enzyme to function properly and thus causes often lethal sideeffects. Whilst toxicity may differ according to the metal species, the most potent forms are those which can be absorbed into the tissues of organisms often causing serious inhibitive effects on the nervous system, physical damage or even death, Heavy metals are known to be toxic metal that can cause severe damage to plants and animals. Heavy metalsinduced oxidative stress involves induction of lipid peroxidation in plants that causes severe damage to cell membranes. Oxidative stress induced by heavy metals initiates the degradation of photosynthetic pigments causing decline in seed germination and seedling growth. High heavy metals concentration can disturb the chloroplast ultrastructure thereby disturbing the photosynthetic process. Heavy metals can affect antioxidant metabolism in plants the test, we concluded that the study isn’t very well designed too。 it is dependent on the age, vegetation state of the plant as well as on zinc availability . Radish are widely growth around the world。關(guān)鍵詞：重金屬；種子萌發(fā)；根；莖；抑制；葉綠素；累積論文類型： 基礎(chǔ)研究AbstractWith the development of global economy, the heavy metal pollutants enter soil by many ways too, and then the soil was polluted by heavy metals seriously. Polluted soil not only effects the plant growth and degrade the quality of food, but also threaten people’s health through the Food Chain, lead to air and water environment polluted too. Heavy metals occur naturally at low concentrations in soils. Heavy metal pollutant was regarded as very important pollutant all around the world. Now the soil around the world was polluted by heavy metals at different degree, totally the heavy metal released to the environment annually nearly as follow: Hg: ton, Cu: 340million ton, Pb: 500million ton, Mn: 1500 ton, Ni: 100million ton . In north of China, many vegetable and food base exist some heavy metal polluted phenomenon seriously, for example, Beijing, Tianjin, Shenyang, Jinan, Changchun, Zhengzhou etc.. On the other hand, South of China seemed to be a little better, but in Fuzhou, Ningbo, Shanghai, Wuhan, Chengdu and some other place, heavy metal pollution has caused serious ecological problems. With the economic development and ecosystem degrade the structure change and nature disaster etc, the sources of soil will be decreased too, so how to control the heavy metal pollution and investigate how the heavy metal environment is very important and some measures should be done. Heavy metal means those 60 element that density exceed to or those 45 element that density exceed to , As and Se are not metal element, but because of their toxicity and other characteristics are much nearly to heavy metals, so we put As and Se as heavy metal pollutant. Because of the biotoxicity of Hg, Cd, Cr, Pb, and As, they have been taken the most important heavy pollutants in the environment, also Zn, Cu, Co, Ni，Se and some other pollutant were regarded very toxic. Heavy metals like Zn, Fe, Cu, Mn are essential for plant growth and important constituents of many enzymes of metabolic importance. Other metals like Pb, Cd, As, Se, Cr and Al are biologically nonessential and toxic above certain threshold levels. It is found in the environment in three major states: chromium (0), chromium (III), and chromium (VI). Chromium (III) occurs naturally in the environment, while chromium (VI) and chromium (0) are generally produced by industrial processes. Cr (III) showed no toxicity effect to plant, but Cr (VI) has very serious toxicity to plant. Excess Cd causes a number of toxic symptoms in plants ., growth retardation, inhibition of photosynthesis. It forms a number of salts, of which the sulfate is most mon。8. 鎘和鋅復(fù)合污染時對蘿卜的萌發(fā)表現(xiàn)為協(xié)同作用。6. 在鉻和鈷復(fù)合處理時，低濃度表現(xiàn)為拮抗作用，較高濃度時，表現(xiàn)為協(xié)同作用。但總?cè)~綠素含量比類胡蘿卜素含量降低的多，葉綠素B的含量比葉綠素A的含量降低得多。在所有重金屬對蘿卜種子的毒性測試下，根和莖比萌發(fā)率更準(zhǔn)確、敏感。 2. 重金屬鎘、鋅單獨(dú)處理時，低濃度處理促進(jìn)了蘿卜種子的萌發(fā)和莖的伸長，高濃度處理時，則受到抑制。通過實(shí)驗(yàn)，得到如下結(jié)論：1. 在重金屬鎘、鉛單獨(dú)處理時，所有蘿卜種子的萌發(fā)率和幼苗生長均受到明顯的抑制。稱取干樣（，），再分別加入１ｍＬ混合酸（65% HNO3:H2O2=4:1）溶解，然后用高壓鍋在120℃下消毒滅菌90分鐘。根和幼芽中重金屬含量的測定也在7天后，重金屬含量的測定用火焰原子吸收測定儀測定。把葉綠體色素提取液倒入光徑1cm的比色杯內(nèi)。用滴管吸取乙醇，將濾紙上的葉綠體色素全部洗入容量瓶中，直至濾紙和殘渣中無綠色為止。靜置35分鐘。1℃，光周期為12小時。在培養(yǎng)皿中放入兩層的濾紙，濾紙分別用蒸餾水（對照實(shí)驗(yàn)）和復(fù)合重金屬的不同濃度的溶液浸濕；每個培養(yǎng)皿中放入50粒種子，然后放入培養(yǎng)箱中，白天溫度為2530177。本次實(shí)驗(yàn)首先篩選飽滿、大小均勻的蘿卜種子用做實(shí)驗(yàn)種子，用流水清洗培養(yǎng)皿3次，再用蒸餾水沖洗，烘干。6H2O ( 132 mg/l), PbCl2 (、 mg/l), HgCl2 (、 、 mg/l) and ZnCl2 (、 mg/l)。實(shí)驗(yàn)中所用的重金屬鹽及濃度如下： CdCl2盡管許多研究都關(guān)注于研究重金屬對植物的影響上，可是很少有注重于對多種環(huán)境因素的相互作用或共同作用上。如今，隨著工業(yè)化、城市化的發(fā)展，污染物包括重金屬進(jìn)入環(huán)境的數(shù)量越來越多，各種疾病的突發(fā)率都與水果和蔬菜的食用緊密相關(guān)。近年來，由于工業(yè)和城市化的發(fā)展中國的很多農(nóng)田被重金屬所污染，而蘿卜往往種植于高速公路附近和礦區(qū)附近的農(nóng)田中。本實(shí)驗(yàn)對蘿卜種子在重金屬污染環(huán)境中的萌發(fā)、早期生長、葉綠素含量、重金屬累積等生理生化指標(biāo)進(jìn)行了初步研究。環(huán)境中的重金屬污染往往會影響到植物的生長、發(fā)育以及種子的萌發(fā)，國內(nèi)外很多學(xué)者和專家對重金屬影響種子萌發(fā)生長等方面做了大量的實(shí)驗(yàn)研究。重金屬還可通過農(nóng)肥，下水道污泥，市政廢棄物以及殺蟲劑等進(jìn)入土壤，重金屬一旦進(jìn)入土壤它的總量就很難減少。特別是對土壤的污染，從而污染了生長在土壤上的植物?？傊亟饘俣拘缘拇笮⊥怯善鋸脑诘男螒B(tài)所決定，毒性大的形態(tài)將被有機(jī)體的組織器官吸收后，或?qū)ι窠?jīng)系統(tǒng)造成嚴(yán)重的影響，或造成生理上的迫害甚至死亡。此外，許多硫酸鹽、碳酸鹽和硫酸鹽將會影響重金屬在非質(zhì)原體和共質(zhì)體中的移動性，這些重金屬非原質(zhì)體的運(yùn)輸很大程度上是由很高的離子交換能力所決定，除非重金屬離子是以非陽離子形式存在。當(dāng)然，重金屬的生物毒性是與其存在的形態(tài)是密不可分的，比如就汞、鉛、砷、鎘來說，當(dāng)它們以陽離子形態(tài)存在時毒性會增加。在中國太原市，土壤中重金屬濃度不僅已超過當(dāng)?shù)氐沫h(huán)境背景值，而且數(shù)量還在不斷增加。早在20世紀(jì)60年代，污水灌溉就成為農(nóng)業(yè)灌溉的重要部分，特別是在中國的北方。其次，重金屬污染是隨著人口數(shù)量的增加、土壤利用率和人類交通工具的增長而不斷加強(qiáng)。首先，一些土壤本身就含有大量重金屬，不同的土壤類型包含的重金屬的量不同，人類活動可以使得土壤中固有的這些重金屬轉(zhuǎn)移到空氣中、水中和其它土壤中，造成重金屬污染。許多研究表明，當(dāng)鉛通過植物的根和莖進(jìn)入植物體內(nèi)后，將在植物體內(nèi)大量積累，然而其積累的量主要取決于鉛本身的特性。鉛的可溶性和不溶性的形態(tài)對于植物都具有毒性作用。蘿卜廣泛生長于世界各地，本次實(shí)驗(yàn)是為了研究鋅對蘿卜種子萌發(fā)及其幼苗生長的影響。另外一些重金屬對植物以及生長具有更大的毒性作用，包括砷、鈷、鋁、硒等。除了汞、 鉛、鎘、鉻之外，土壤中還有其它的金屬元素。造成汞對蘿卜根生長和莖生長的抑制能力遠(yuǎn)遠(yuǎn)大于對蘿卜種子萌發(fā)的抑制力的原因可能是由于汞在蘿卜的根和莖中的積累到一定量時造成抑制性最大。其中汞對蘿卜根生長和莖生長的抑制能力遠(yuǎn)遠(yuǎn)大于對蘿卜種子萌發(fā)的抑制力，原因可能在于是蘿卜種皮對種子萌發(fā)的保護(hù)作用，當(dāng)種子萌發(fā)