【作者】 孙永红；

【导师】 梁永超；

【作者基本信息】 南京农业大学 ， 植物营养学， 2008， 博士

【摘要】 近年来,土壤污染成为全球性的环境问题,重金属的复合污染问题已经引起国内外学者的普遍关注。水稻是中国乃至全亚洲国家的主要粮食作物,Cd、As又易于在水稻籽粒中积累,然而,对重金属在水稻体内吸收转运的机理及元素间的相互作用仍存在较多的争议。本研究综合土培、水培和砂培等培养条件,以水稻为试验材料,较为系统的研究了在不同培养条件下Cd、As胁迫对水稻生长的影响、Cd、As在水稻体内的相互作用及吸收分配,通过添加硅、钙肥来减少Cd、As向水稻地上部特别是籽粒中的转运,结合透射电镜观察Cd、As胁迫下水稻根部细胞的亚细胞结构和重金属沉积情况,探索影响Cd、As向水稻地上部转运的生物学机制。主要研究结果如下:1经Cd、As单一及复合污染处理后,水稻生长受到严重的影响,在As浓度为4 mg·L^-1,Cd浓度为0.5 mg·L^-1时,苗期水稻根的生物量为对照的51.7%;茎叶的生物量为对照的42.6%。而且4 mg·L^-1As的单一和复合处理对株高、穗长、千粒重、每穗实粒数和产量等农艺性状的影响也极为显著（p＜0.01）。Cd、As之间存在拮抗作用,As减少了水稻对Cd的吸收。随着As浓度的增加,植株的根部、茎叶、糙米和谷壳中的Cd含量呈降低趋势。2增加营养液中的亚铁离子浓度缓解了4 mg·L^-1水平的As处理对水稻茎叶生长的抑制。与单一Cd、As污染相比,在Cd、As复合污染条件下,增加水稻根表铁的富集,与0 mg·L^-1Fe²⁺水平相比,50 mg·L^-1水平的茎叶干物重提高了19.4%。Fe²⁺减少了水稻对Cd的吸收,在50 mg·L^-1Fe²⁺水平时,茎叶中的Cd浓度为0 mg·L^-1Fe²⁺水平的16.7%。同时,Fe²⁺减少了水稻对As的吸收,在30 mg·L^-1 Fe²⁺和50 mg·L^-1 Fe.（2+）水平时茎叶的As含量分别为0 mg·L^-1 Fe²⁺水平的59.2%和52.2%。3比较淹水、饱和含水量、75%饱和含水量三种不同水分处理对Cd、As交互下水稻茎叶和根部Cd、As含量影响发现,在淹水时水稻各部位的Cd、As含量较低。4 Cd、As单一胁迫显著影响了水稻在红壤上的生长发育,降低了水稻的生物量,而Cd与As共同作用时则表现为拮抗作用,与单一Cd、As处理相比,复合处理的水稻叶片SOD和POD酶活性升高,GSH和ASA含量也显著增加,在水稻成熟期,汕优63和武育粳3两个水稻品种的稻谷产量都增加,同时,复合污染处理显著降低了水稻茎叶和籽粒对Cd、As的富集,茎叶处理之间差异显著。5红壤中添加了碳酸钙和硅酸钠以后,促进了苗期水稻的生长,尤其在处理后20天和40天时生物量增加显著,而且水稻根部和地上部对Cd、As的吸收减少。同时,碳酸钙和硅酸钠处理增加了两个水稻品种的株高、穗长、每穗的实粒数和千粒重,但高量的碳酸钙和硅酸钠减少了两个水稻品种的有效分蘖数,不利于水稻的干物质积累。添加碳酸钙和硅酸钠处理显著降低了两个水稻品种茎叶、根、糙米和谷壳的Cd含量（P＜0.05）,同时,各部分的As含量也呈降低趋势,且随着添加量的增加,降低幅度显著。6水稻幼苗加硅处理增加了Cd、As胁迫下水稻根部SOD、POD和PPO三种酶的活性,在50μM As处理水平下,加硅处理水稻根的SOD、POD和PPO的活性分别比不加硅处理增加了60.7%、49.8%和19.2%;在100μM As处理水平分别提高了21.9、21.8%和22.6%。水稻加硅缓解了Cd、As胁迫对光合作用产生的抑制,减少了Cd、As胁迫造成的根细胞的细胞死亡程度,缓解了Cd、As胁迫造成细胞器的损伤。在Cd、As胁迫的细胞壁上,还观察到分布较为规律的颗粒沉积。更多还原

【Abstract】 Recently,soil contamination with heavy metals has become a global problem.With the complexity of the sources of contamination,heavy metal contamination has aroused the widespread concern of scholars at home and abroad.Rice is the main food crop in China and even in Asia and is easy to accumulate heavy metals such as cadmium and arsenic in its grain.However,information is still sacnt and even controversial on the absorption and transportation of heavy metals in plant and the interactions between the metals.A series of experiments with rice were conducted to study the interaction between cadmium and arsenic,the effect of cadmium and arsenic stress on the plant growth,cadmium and arsenic absorption and partitioning,effect of calcium carbonate and sodium silicate on mitigating cadmium and arsenic stresses.In addition,transmission electron microscopy（TEM） was used to analyze root ultrastructure and distribution pattern of cadmium and arsenic in organs and organelles.The results obtained were presented as follows.1.Single and combined cadmium and arsenic treatment decreased the rice biomass.The root and shoots dry mass of rice seedlings were 42.6%and 51.7%of the control, respectively.Under 4 mg·L^-1 As stress the rice height,spike length,1000-grain weight, and grains per panicle were significantly decreased.Significant interaction was observed between Cd and As.As concentrations in roots,shoots,chaff and brown rice decreased significantly with increasing of Cd concentrations in nutrient solution. Moreover,increasing As concentration in the solution significantly reduced Cd concentration.2.There are some interactions among Cd,As and iron.Appropriate iron nutrient supply had a beneficial influence on Cd and/or As stressed rice plant.The data indicated that the combined treatment with Cd and As significantly increased the iron concentration on the root surface.The Cd and As concentrations in roots and shoots were decreased in the treatment with 30 mg Fe²⁺·L^-1 compared with the control,while the Cd and As concentrations in roots and shoots increased slowly in the treatment with 50 mg Fe²⁺·L^-1.Addition of 50 mg Fe²⁺·L^-1 increased the shoot dry mass by 19.4%in comparison with non-Fe²⁺treatment.Cd concentration of 50 mg Fe²⁺·L^-1 treatment in rice shoots was 16.7%ofnon-Fe²⁺ treatment.Moreover,As concentration office shoots at 30 and 50 mg Fe²⁺·L^-1 level were 59.2%and 52.2%of the control,respectively.3.A sand culture experiment was carried out to investigate the effect of water regimes on Cd and As uptake and rice growth.The results indicated that the flooding treatment decreased the Cd and As concentrations in roots and shoots compared with the treatment with moisture content of 75%sand water capacity.4.Two contrasting rice（Oryza sativa L.） cultivars,i.e.Wuyujing3 and Shanyou63,were grown in red soil to study the toxicity of As and Cd（individually or in combination） on rice seedlings.Results showed that both As and Cd treatments decreased root biomass and shoot biomass compared with the corresponding controls（neither Cd nor As treatment）.However,the treatment with As significantly mitigated the Cd-induced inhibition of shoot growth for SY63,root and growth for WYJ3.Both As and Cd exposures significantly decreased the SOD and POD activities,GSH and AsA levels, while the As plus Cd treatment mitigated the decreasing effect compared with Cd treatment alone（p＜0.05）.The As plus Cd treatment significantly decreased As or Cd levels both in roots and in shoots compared with the As treatment alone,or Cd treatment alone,respectively.The very similar trend was also found in Cd and As contents of different organs office at the maturity stage（p＜0.05）.5.A pot experiment was conducted to study the effect of sodium silicate and calcium carbonate on Cd and As uptake by rice grown in a red soil experimentally contaminated with Cd and As.The results showed that addition of silicate or carbonate signifcantly increased the plant height,panicle length,1000-grain weight,and grains per panicle compared with the treatment with Cd and As alone.However,application of sodium silicate and calcium carbonate at higher rates significantly decreased the number of effective tillers and Cd and As contents of different organs office at the maturity stage.6.Silicon treatment increased the SOD and POD activities,biomass production,and the net photosynthetic rate in rice grown hydroponically with Cd or As stress.Silicon increased SOD,POD and PPO activities in rice roots exposure at 50μmol·L^-1 As by 60.7%,49.8%and 19.2%,respectively compared with non silicon treatments. Transmission Electron Microscope（TEM） analysis showed:that serious untrastructural damage was observed in rice roots treated with 50μmol·L^-1 Cd or 100μmol·L^-1 As individually.Plasmolysis,concentrated cytoplasm,ambiguity of organelle were all symptoms of root cells under heavy metal stress.Some vacuole and irregular thickening cell wall were found on the stressed cells.And there existed some different granules in these cell walls.更多还原