摘要
镉(Cadmium,Cd)是环境中毒性最强的重金属元素之一,其引起的生态环境问题一直是环境科学研究的热点。本研究以杂交杨(Populus deltoides×Populus nigra)为材料,通过盆栽试验研究了紫色土和冲积土中不同浓度的Cd处理对杨树生长和C、N、P元素积累的影响以及Cd在土壤-杨树系统中的迁移与分配特征,以期为Cd污染土壤的无害化利用、城市森林建设和速生丰产林基地建设等提供一定科学依据。研究结果表明:
1.土壤中低浓度的Cd污染对杨树叶片的净光合速率有一定的抑制作用,处理浓度相同时,冲积土杨树叶片的净光合速率高于紫色土杨树。紫色土中,低浓度Cd对叶片气孔导度有显著促进作用,胞间二氧化碳浓度和气孔导度一致增加,而在冲积土中变化不显著。低浓度Cd处理对叶片蒸腾速率的影响不显著。杨树叶片叶绿素a、叶绿素b的含量以及叶绿素a/b在冲积土Cd处理环境中没有显著变化,而在紫色土Cd处理环境中,叶绿素a的含量显著减少。冲积土中,不同的密度对杨树在光合作用和叶绿素含量的影响不显著。单株杨树的叶面积随Cd浓度的增大而减小,Cd处理对杨树的叶面积的生长有显著影响。冲积土中,处理相同的不同密度之间,密度的增加对杨树单株叶面积生长产生了抑制。
2.低浓度Cd处理对杨树高和地径的生长无显著的影响,不同的土壤对杨树生长的影响更显著,相同的处理浓度下高生长和地径的生长均表现为冲积土显著高于紫色土。冲积土中,密度对杨树生长的影响较低浓度的Cd处理明显。低浓度的Cd处理对杨树根部、茎部、凋落叶的生物量生长与分配均无显著的影响,紫色土中,根部、茎部和凋落叶生物量占总的生物量的分配比例大致为0.53:0.27:0.20,而冲积土中这一比例约为0.38:0.42:0.20。不同的土壤之间生物量的生长与分配差异显著,栽植密度增大单株杨树生物量生长受到抑制。
3.土壤-植物系统中,随着处理浓度的增大,杨树吸收积累Cd的量增大,土壤中Cd的含量减小,凋落叶归还到土壤中的Cd的量呈现无规律性的变化,但总体上紫色土归还的量较冲积土小。单株杨树Cd的积累量随处理浓度的增大而增加。Cd在杨树不同器官之间的分配,在紫色土中,根部、茎部和凋落叶Cd的积累量占总积累量的比例大至为0.545:0.453:0.002,冲积土中的比例为0.416:0.577:0.007。杨树在紫色土中将吸收的Cd主要储藏在根部,而冲积土中Cd则主要分布在茎部。栽植密度增大单株杨树所积累的Cd的量减少。
4.低浓度Cd处理对杨树C、N和P积累量的影响并不显著,不同的土壤间差异明显,冲积土中处理相同时,杨树各器官中的积累量不同密度间的差异显著。杨树各器官C的积累量在紫色土中为根部>茎部>凋落叶,其比例为大致为0.49:0.33:0.18;冲积土中为茎部>根部>凋落叶,比例约为0.37:0.42:0.21。杨树各器官N的积累量在紫色土CK中根部、茎部、凋落叶的分配比例为0.56:0.22:0.22,其余处理的分配比大致为0.50:0.18:0.32;冲积土中T3处理根茎叶分配为0.39:0.26:0.35,其余处理的分配比例大致为0.35:0.28:0.37。紫色土中,CK处理时P在根、茎、凋落叶中的分配比例为0.47:0.30:0.23,其余处理中的比例为0.50:0.23:0.27;冲积土中根部、茎部、凋落叶中P的积累量的比例为0.35:0.39:0.26。
Cadmium is one of heavy metal elements which are of high toxicity in environment. The ecological environmental problems induced by cadmium are hotspots were widely studied in environmental science.In this paper,potted hybridized popular tree was used to study the effect of different Cd concentrations in purple soil and alluvial soil on the growth and C,N,P accumulation of P.deltoids×P.nigra as well as Cd migration and distribution, which provided certain scientific basis for making innoxious use of Cd polluted soil, construction of urban forest and construction of fast-growing and high-yield plantation base.The results showed that:
1.Low concentration of Cd pollution in the soil have inhibited effect on net photosynthetic rate of P.deltoids×P.nigra tree leaves to an extent,which were higher in alluvial soil than in purple soil at the same Cd concentration treatment.In purple soil,low Cd concentration can promote stomata conductance significantly,Carbon dioxide concentration among cells also increased with stomata conductance.While in alluvial soil, these changes were not significant and low Cd concentration had no significant effect on transpiration rate.Content of chlorophyll a,chlorophyll b and their proportion in P. deltoids×P.nigra leaves in alluvial soil were not significant affected by Cd treated.But content of chlorophyll a in P.deltoids×P.nigra leaves in purple soil were reduced significantly under Cd treated environment.In alluvial soil,planting density had no significant effect on photosynthesis and chlorophyll content of P.deltoids×P.nigra.Leaf area of individual tree decreased along with the increase of Cd concentration.Cd treatment had a significant effect on leaf area of P.deltoids×P.nigra.In alluvial soil,different densities with the same treatment were studied.Leaf area growth of individual tree was inhibited by density increase.
2.Low Cd concentration treatment showed no significant effect on the tree height and ground diameter of P.deltoids×P.nigra,however,the difference of soil type showed obvious effect,effect on the tree height growth and ground diameter growth in alluvial soil were higher than that in purple soil at the same Cd concentration treatment.In alluvial soil, effect of density on growth of P.deltoids×P.nigra was more obvious than that of low Cd concentration treatment.Low Cd concentration had no significant effect on the biomass growth and distribution in root,stem and defoliation of P.deltoids×P.nigra.In purple soil, ration of biomass percentage in root,stem,defoliation to total plant biomass was 0.53:0.27: 0.20,which was 0.38:0.42:0.20 in alluvial soil.Biomass growth and distribution of trees in different soil type were of significant difference,increase of planting density showed inhibition on biomass growth of individual plant.
3.In the soil-plant system,Cd volume taken up by tree was increased and Cd volume in soil was reduced with the increase of treated concentration.Cd volume that was returned to soil through defoliation varied irregularly.Generally,the total Cd volume returned by defoliation in purple soil was less than that in alluvial soil.Cd accumulation in individual plant increased with the increase of treated Cd concentration,which indicated that treated Cd concentration had a positive correlation with plant Cd accumulations to an extent.Cd volume distributions in different organs of P.deltoids×P.nigra were as follows:In purple soil,Cd volume in root,stem and defoliation was 0.545:0.453:0.002 in proportion,while in alluvial soil that was 0.416:0.577:0.007.Cd were mainly stored in root of P.deltoids×P.nigra planted absorbed from purple soil,but in alluvial soil,the absorbed Cd was mainly stored in stem.Increase planting density reduced the Cd accumulation in individual plant.
4.Low Cd concentration had no significant effect on the C,N and P accumulation in P.deltoids×P.nigra.But C,N and P accumulations were different in different soil types. In alluvial soil with same treatment,C,N and P accumulations in tree organs were significantly different under different planting density.In purple soil,C accumulations were ranked in descending order as:root(0.49)>stem(0.33)>defoliation(0.18),while in alluvial soil was stem(0.37)>root(0.42)>defoliation(0.21).In purple soil,N accumulations in CK were root(0.56),stem(0.22),and defoliation(0.22);in other treatments were root(0.50),stem(0.18),and defoliation(0.32).In alluvial soil,under T3 treatment the N accumulation in root,stem,and defoliation was 0.39,0.26,and 0.35 separately;while under other treatments were root(0.35),stem(0.28),and defoliation (0.37) respectively.In purple soil,P accumulations in CK were root(0.47),stem(0.30), defoliation(0.23),under other treatments was root(0.50),stem(0.23),defoliation(0.27), and in alluvial soil all treatments were as root(0.35),stem(0.39),and defoliation(0.26).
引文
[1]王焕校.污染生态学[M].北京:高等教育出版社,2000,p:191~192.
[2]孟紫强.生态毒理学原理与方法[M].北京:科学出版社,2006,p:171~245.
[3]杨万勤,张健.土壤生态研究[M].成都:四川科学技术出版社,2008,p:188~189.
[4]孙铁珩,周启星,李培军.污染生态学[M].北京:科学出版社,2001,p:132~133.
[5]郭亚平,胡曰利.土壤-植物系统中重金属污染及植物修复技术[J].中南林学院学报,2005,2(4):59~62.
[6]孙铁珩,李培军,周启星.土壤污染形成机理与修复技术[M].北京:科学出版社,2005,p:2~3.
[7]赵其国,周炳中,杨浩,等.中国耕地资源安全问题及其相关对策思考[J].土壤,2002,6,293~302.
[8]夏家淇,骆永明.我国土壤环境质量研究几个值得探讨的问题[J]_生态与农村环境学报,2007,23:1~6.
[9]赵中秋,朱永官,蔡运龙.镉在土壤-植物系统中的迁移转化及其影响因素[J].生态环境,2005,14(2):282~286.
[10]张军,束文圣.植物对重金属镐的耐受机制[J].植物生理与分子生物学学报,2006,32(1):1~8.
[11]周青,黄晓华,施国新.镉对5种常绿树木若干生理生化特性的影响[J].环境科学研究,2001,14(3):9~11.
[12]徐爱春,陈益泰,王树凤,等.镉胁迫下柳树5个无性系生理特性的变化[J].生态环境,2007,16(2):410~415.
[13]邓培雁,刘威,韩博平.宝山堇菜(Viola baoshanensis)镉胁迫下的光合作用[J].生态学报,2007,27(5):1858~1862.
[14]郭智,王涛,奥岩松.镉对龙葵幼苗生长和生理指标的影响[J].农业环境科学学报,2009,28(4):755~760.
[15]Jarup L,Akesson A.Current status of cadmium as an environmental health problem[J].Toxicology and Applied Pharmacology,2009,doi:10.1016/j.truap.2009.04.020.
[16]Nordberg GF.Historical perspectives on cadmium toxicology[J].Toxicology and Applied Pharmacology,2009,doi:10.1016/j.taap.2009.03.015.
[17]Joseph P.Mechanisms of cadmium carcinogenesis[J].Toxicology and Applied Pharmacology,2009,doi:10.1016/j.taap.2009.01.011.
[18]马静,易建华.镉致肾脏损伤的研究概况[J].2009,36(1):34~37.
[19]张从,夏立江.污染土壤生物修复技术[M].北京:中国环境科学出版社,2000,p:12~13.
[20]金彩霞,周启星,孙瑞莲,等.根.土界面镉的生态化学行为与毒理效应研究进展[J].应用生态学报,2005,16(8):1553~1557.
[21]李森,亢秀平,邢国明.影响植物吸收镉的因素[J].北方园艺,2007,7:76~78.
[22]杨居荣,贺建群,黄翌,等.农作物Cd耐性的种内和种间差异Ⅰ.种间差[J].应用生态学报,1994,5(2):192~196.
[23]关伟,王有年,师光禄,等.两个桃树品种对土壤中不同镉水平的响应[J].生态学杂志,2007, 26(6):859~864.
[24]曹莹,刘洋,王国骄,等.铅-镉复合胁迫下玉米品种间积累铅、镉的差异[J].玉米科学,2009,17(1):80~85.
[25]陈瑛,李廷强,杨肖娥,等.不同品种小白菜对镉的吸收积累差异[J].应用生态学报,2009,20(3):736~740.
[26]Liu WT,Zhou QX,Sun YB,etal.Identification of Chinese cabbage genotypes with low cadmium accumulation for food safety[J].Environmental Pollution,2009,157 1961~1967.
[27]廖敏,谢正苗,黄昌勇。镉在土水系统中的迁移特征[J].土壤学报,1998,35(2):179~185.
[28]Lepp NW,Madejon P.Cadmium and zinc in vegetation and litter of a voluntary woodland that has developed on contaminated sediment-derived soil[J].J.Environ.Qual.,2007,36:1123~1131.
[29]Wei SH.,Zhou QX,Koval PV.Flowering stage characteristics of cadmium hyperaccumulator Solanum nigrum L.and their significance to phytoremediation[J].Science of The Total Environment,2006,369:441~446.
[30]王宏镔,束文圣,蓝崇钰.重金属污染生态学研究现状与展望[J].生态学报,2005,25(3):596~605.
[31]Lu LL,Tian SK,Yang XE,etal.Cadmium uptake and xylem loading are active processes in the hyperaccumulator Sedum alfredii[J].Journal of Plant Physiology,2009,166:579~587.
[32]周启星,魏树和,张倩茹,等.生态修复[M].北京:中国环境科学出版社,2006,p:127~131.
[33]刘威,束文圣,蓝崇钰.宝山堇菜(Viola baoshaensis)--一种新的镉超富集植物[J].科学通报,2003,48(19):2046~2049.
[34]魏树和,周启星,王新.超积累植物龙葵及其对镉的富集特征[J].环境科学,2005,26(3):167~171.
[35]聂发辉.镉超富集植物商陆及其富集效应[J].生态环境,2006,15(2):303~306.
[36]许文宝,谢志南,刘鸿洲,等.龙眼对镉的吸收分布特性及耐性研究[J].亚热带植物科学,2007,36(03):1~3.
[37]徐爱春.柳树无性系镉积累和生理变化规律研究.北京:中国林业科学研究院博士学位论文,2007.
[38]张金彪,黄维南.镉胁迫对草莓光合的影响[J].应用生态学报,2007,18(7):1673~1676.
[39]万雪琴,张帆,夏新莉,等.镉处理对杨树光合作用及叶绿素荧光参数的影响[J].林业科学,2008,44(6):73~78.
[40]曾翔,张玉烛,王凯荣,等.镉对水稻种子萌发的影响[J].应用生态学报,2007,18(07):1665~1668
[41]Carpena RO,Vazquez S,Esteban E,etal.Cadmium-stress in white lupin:effects on nodule structure and functioning[J].Plant Physiology and Biochemistry,2003,41(I0):911~919.
[42]Devi R,Munjral N,Gupta AK.Cadmium induced changes in carbohydrate status and enzymes of carbohydrate metabolism,glycolysis and pentose phosphate pathway in pea[J].Environmental and Experimental Botany,2007,61(2):167~174.
[43]王宏镔,王焕校,文传浩,等.镉处理下不同小麦品种几种解毒机制探讨[J].环境科学学报,2002,22(04):523~528.
[44]张玲,王焕校.镉胁迫下小麦根系分泌物的变化[J].生态学报,2002,22(04):496~502.
[45]范洪黎,周卫.镉超富集苋菜品种(Amaranthus mangostanus L.)的筛选[J].中国农业科学, 2009,42(4):1316~1324.
[46]鲍士旦.土壤农化分析[M].中国农业出版社,2000.
[47]秦天才,阮捷,王腊娇.镉对植物光合作用的影响[J].环境科学与技术,2000,Z1:33~35.
[48]黄会一,张春兴,张有标.重金属镉、铅对木本植物光合作用影响的初步研究[J].生物学杂志,1986,5(2):6~9.
[49]赵素达,付成秋,朱松龄.镉对石莼光合作用和呼吸作用及叶绿素含量的影响[J].青岛海洋大学学报,2000,30(3):519~523.
[50]余东,李永裕,邱栋梁,等.镉(Cd)胁迫对枇杷生长和光合速率的影响[J].农业环境科学学报,2007,26(增刊):33~38.
[51]张金彪,黄维南.镉对植物的生理生态效应的研究进展[J].生态学报,2000,20(3):514~523.
[52]周云龙.植物生物学(第二版)[M].北京:高等教育出版社.2004.
[53]Smith G.C,Brennan EG,Grenhalgh BJ.Cadmium sensitivity of soybean related to efficiency in iron utilization[J].Environ.Experi.Bot.,1985,25(2):99~106.
[54]Walker WM,Miller JE,Hassett JJ.Effects of Pb and Cd upon the Ca,Mg,K and P concentration in young corn plant[J].Soil science,1977,124:145~151.
[55]Farquhar GD,Sharkey TD.Stomatal conductance and photosynthesis[J].Annual Review of Plant Physiology,1982,33:317~345.
[56]章家琪,吴燕玉.镉污染与农业[M].北京:科学普及出版社,1989,p:23~25.
[57]陈怀满.土壤中化学物质的行为与环境质量[M].北京:科学出版社,2002,p:102~104.
[58]张晓熹,罗泉达,郑瑞生,等.石灰对重金属污染土壤上镉形态及芥菜镉吸收的影响[J].福建农业学报,2003,18(3):151~154.
[59]杨忠芳,陈岳龙,钱鑂,等.土壤pH对镉存在形态影响的模拟实验研究[J].2003,12(1):252~261.
[60]王忠.植物生理学IM].北京:中国农业出版社,2000,p:221.
[61]Broadley M R,Escobar-Gutierrez A J,Burns A,et al.What are the effects of nitrogen deficiency on growth components of lettuce?[J].New Phytologist,2000,147:519~526.
[62]王忠.植物生理学[M].北京:中国农业出版社,2000,p:85.