简介：Background:Ecologistsareinterestedinassessingthespatialandtemporalvariationinecologicalsurveysrepeatedovertime.Thispapercomparesthe1985and2015surveysoftheBarroColoradoForestDynamicsplot(BCI),Panama,dividedinto1250(20m×20m)quadrats.Methods,spatialanalysis:TotalbetadiversitywasmeasuredasthetotalvarianceoftheHellinger-transformedcommunitydatathroughouttheBCIplot.Totalbetawaspartitionedintocontributionsofindividualsites(LCBDindices),whichweretestedforsignificanceandmapped.Results,spatialanalysis:LCBDindicesindicatedthesiteswithexceptionalcommunitycomposition.In1985,theyweremostlyfoundintheswamphabitat.Inthe2015survey,noneoftheswampquadratshadsignificantLCBDs.Whathappenedtothetreecommunityintheinterval?Methods,temporalanalysis:Thedissimilarityincommunitycompositionineachquadratwasmeasuredbetweentime1(1985)andtime2(2015).TemporalBetaIndices(TBI)werecomputedfromabundanceandpresence-absencedataandtestedforsignificance.TBIindicescanbedecomposedintoB=species(orabundances-per-species)lossesandC=species(orabundances-per-species)gains.B-Cplotswereproduced;theydisplayvisuallytherelativeimportanceofthelossandgaincomponents,throughtime,acrossthesites.Results,temporalanalysis:InBCI,quadratswithsignificantTBIindiceswerefoundintheswamparea,whichisshrinkinginimportanceduetochangestothelocalclimate.ApublishedhabitatclassificationdividedtheBCIforestplotintosixhabitatzones.GraphsoftheBandCcomponentswereproducedforeachhabitatgroup.Group4(theswamp)wasdominatedbyspecies(andabundances-per-species)gainswhereasthefiveotherhabitatgroupsweredominatedbylosses,somegroupsmorethanothers.Conclusions:WeidentifiedthespeciesthathadchangedthemostinabundancesintheswampbetweenT1andT2.Thisanalysissupportedthehypothesisthattheswampisdryingoutandisinvadedbyspeciesfr

简介：甘氨酸甜菜碱是植物细胞内一种重要的调渗物质，盐胁迫下，甘氨酸甜菜碱的积累可以保护细胞内蛋白质的结构和功能，降低细胞水势，从而增强植物自身的耐盐能力。从大肠杆菌中克隆的胆碱脱氢酶基因（betA）是甘氨酸甜菜碱合成的关键酶基因，该基因编码的胆碱脱氢酶（CDH）可将胆碱一步合成为甜菜碱。本实验室已将胆碱脱氢酶基因（betA）转入到小黑杨花粉植株基因组中，并最终获得了4个转基因株系。本研究以4个转betA基因株系（TB1、TB2、TB3、TB4）及非转基因对照为试材，在浓度为1．2％的NaCl盐胁迫下，测定其甜菜碱含量、超氧化物歧化酶（SOD）活性、过氧化物酶（POD）活性和丙二醛（MDA）含量，并调查试材的盐害情况，计算盐害指数，目的是为了研究转基因株系的耐盐效果，从中筛选出耐盐能力较强的转基因株系。试验结果表明，4个转基因株系的甜菜碱含量均高于非转基因对照；在1．2％NaCl胁迫下TB1、TB2、TB3的超氧化物歧化酶活性、过氧化物酶活性均高于非转基因对照，TB3低于对照：TB1、TB4的丙二醛含量低于对照，TB2、TB3与对照相近。进一步的盐害分析表明4个转基因株系中的TB1和TB4株系的盐害指数低于对照的42．1％和33．4％，TB2、TB3与对照无显著差异。综合各转基因株系的耐盐性及生理指标测定结果，4个转基因株系中，TB1、TB2的耐盐性明显优于对照，有希望用于盐碱地造林及推广。