Phenotypic plasticity of invasive Alternanthera philoxeroides in relation to different water availability, compared to its native congener

Phenotypic plasticity and genetic differentiation are two possible mechanisms that plants use to cope with varying environments. Although alligator weed (Alternanthera philoxeroides) possesses very low genetic diversity, this alien weed has successfully invaded diverse habitats with considerably varying water availability (from swamps to dry lands) in China. In contrast, its native congener (Alternanthera sessilis) has a much narrower ecological breadth, and is usually found in moist habitats. To understand the mechanisms underlying the contrasting pattern, we performed a greenhouse experiment to compare the reaction norms of alligator weed with those of its native congener, in which water availability was manipulated. Our results revealed that the two congeners had similar direction of phenotypic plasticity. However, A. philoxeroides showed greater plasticity in amount than did A. sessilis in many traits examined during the switch from wet to drought treatment. Nearly all of the phenotypic variance in A. philoxeroides could be ascribed to plasticity, while A. sessilis had a much higher fraction of phenotypic variance that could be explained by genotypic variation. These interspecific differences in plastic responses to variable water availability partially explained the difference in spatial distribution of the two congeners.     

中华雏蝗（Chorthippus chinensis Tarb）线粒体基因组分析

采用Lon-PCR扩增线粒体全基因组和保守引物步移法结合克隆方法测定并拼接获得了中华雏蝗（Chorthippus chinensis Tarb）线粒体基因组全序列．序列的注释和分析结果表 明,中华雏蝗线粒体基因组序列全长15 599 bp,共有13个编码蛋白质基因、22个tRNA基因、2个rRNA基因和1个A+T富集区．基因顺序与非洲飞蝗（Locusta migratoria）相同,也发生了2个 tRNA Asp(D)和tRNALys(K)的倒置．13个编码蛋白质基因都使用了ATN作为起始密码子．除ND1以TAG和ND5的终止密码子为不完全的T外,其余11个编码蛋白质基因的终止密码子都为完整的TAA．6种直翅类昆虫13个蛋白质的氨基酸序列的联合数据集构建的系统树与形态分类系统一致,中华雏蝗与非洲飞蝗为姐妹群,并与东方蝼蛄构成一单系群．     

喜旱莲子草和接骨草竞争对模拟增温的响应

研究外来入侵植物与本地植物种竞争对气候变暖的响应, 对于预测未来气候变化背景下入侵植物的入侵趋势、理解其入侵机制以及筛选生态替代种具有重要的意义。以入侵我国的外来植物喜旱莲子草(Alternanthera philoxeroides)和本地植物种接骨草(Sambucus chinensis)为材料, 通过两种植物单栽、纯栽和混栽, 采用红外辐射加热器模拟增温, 研究了两种植物竞争对模拟增温的响应。结果表明: (1)在模拟增温期间(2013年5-12月), 增温组空气平均温度比不增温组提高了0.47 ℃, 相对湿度降低了1.87%; (2)混栽的喜旱莲子草除根冠比与单栽无显著差异外, 其余各生物量和根系形态指标均显著低于单栽喜旱莲子草; 无竞争、种间竞争和种内竞争三种竞争间, 接骨草除根冠比、细根与总根生物量比、比根长和比根表面积无显著差异外, 其余指标均呈现无竞争>种间竞争>种内竞争的趋势; (3)无竞争、种间竞争和种内竞争三种条件下, 喜旱莲子草各指标在增温和不增温处理间差异均不显著, 而接骨草总生物量和根生物量在无竞争和种间竞争条件下增温处理均显著低于不增温处理, 在种内竞争条件下则相反; (4)增温使接骨草的相对拥挤系数降低, 接骨草对温度升高反应敏感, 而喜旱莲子草则表现出一定的适应性。由此推测, 在中度遮阴陆生生境中, 接骨草有望成为喜旱莲子草生物替代控制的材料。     

咸水灌溉条件下土壤水盐分布特征

通过设置3种灌水量水平（100%ET_c、80%ET_c、60%ET_c）和3种灌水水质水平（0.7、3和6 g·L^-1）,研究了咸水灌溉条件下春小麦120 cm土层内水分动态和盐分累积特征.结果表明：水分在农田土壤中的分布主要受灌水量和土壤质地的影响,充分灌溉使水分存贮在较深土层中,而非充分灌溉则使水分存贮在表层;在相同灌水量的条件下,土体内的盐分积累程度随着灌溉水矿化度的增大而加剧;在相同矿化度条件下,土体内的盐分含量及积盐深度随着灌水量的增加而增大.在作物整个生育期内,连续使用咸水灌溉将导致土壤积盐,且非充分灌溉较充分灌溉更易使土壤表层积盐.     

好气条件下不同形态外源砷在土壤中的转化

在35%的田间持水量下,通过模拟试验研究了外源二甲基砷酸盐（DMA）、一甲基砷酸盐（MMA）、五价无机砷［As(V)］在土壤中的形态转化.结果表明: 外源砷进入土壤后,其含量均有随时间推延而逐渐下降的趋势,两种不同形态的有机砷DMA和MMA在土壤中主要发生脱甲基化过程,经150 d的恒温恒湿培养,其在土壤中主要转化为As(V),DMA处理仅在120 d时检测到少量MMA,而MMA处理则在7～60 d内均有少量的DMA生成.培养结束时土壤中DMA和MMA含量均显著降低(P<0.01),降幅分别为99.5%、94.3%,而两者的主要转化产物As(V)的含量则分别显著增加了4.61和5.15倍.表明外源有机态砷在土壤中基本上被转化为无机形态;与有机态外源砷相比,外源As(V)进入土壤后其形态基本上没有发生转化.     

Invasion by alligator weed,Alternanthera philoxeroides,is associated with decreased species diversity across the latitudinal gradient in China

Aims Invasive species occurrence and their effects on biodiversity may vary along latitudes. We examined the occurrence (species cover) and relative dominance (importance value) of invasive alligator weed, Alternanthera philoxeroides, in its terrestrial habitat in China through a large-scale latitudinal field investigation.Methods We established 59 plots along the latitudinal transect from 21°N to 37°N. We recorded species name, abundance, height and individual species coverage of plants in every quadrat. We then measured α-species diversity variations associated with the A. philoxeroides community across the latitudinal range. We also analyzed the effect of latitude on plant species' distributions in this community by using canonical correspondence analysis (CCA).Important findings We found that species cover and importance value of A. philoxeroides increased in areas <35°N, but decreased at higher latitudes. Lower latitudes supported greater species diversity than higher latitudes. Small-scale invasion of A. philoxeroides was associated with higher species diversity, but community diversity was lower when A. philoxeroides species cover exceeded 36%. Community plant species changed from mesophyte to hygrophyte gradually from low to high latitude. Our research suggests that latitude had significant influences on community diversity which interacted with the biotic resistance of a community and impact of invasion. Consequently, A. philoxeroides may become more invasive and have greater negative impacts on community species diversity in higher latitudes as global climate changes.     

香根草和水花生对垃圾污水中N、P、CI的吸收效果

香根草和水花生对垃圾污水中不同“污物”的吸收能力差别较大。二者对Ｎ的吸收量均超过了各自净化的 总Ｎ量,对Ｐ的吸收率亦较高,但植株体内的Ｐ浓度却随介质Ｐ浓度的升高而下降。和净化量相比,植物对低浓度 污水中ＣＩ的吸收率较高,但对高浓度中的吸收率较低。和原液中的“污物”量相比时,根系对元素的吸收率都明显 降低。这表明,植物净化系统中的去污方式除了根系的吸收外,还有其他方式,即根系是通过根际微生态系统的综 合作用来达到净化目的。总的来说,香根草对“污物”的吸收能力不比水花生强,尽管他比水花生有更强的净化能 力。     

油菜素内酯对低氧胁迫黄瓜幼苗根系多胺、ATPase活性及无机离子含量的影响

研究了24-表油菜素内酯(EBR)对低氧胁迫黄瓜幼苗根系多胺、ATPase活性及无机离子含量的影响.结果表明,低氧导致根系内多胺(PAs)含量显著提高、(精胺+亚精胺)/腐胺的比值下降,而K+、Ca2+、Mg2+、Zn2+含量及ATPase活性显著下降;与单纯的低氧处理相比,EBR可增加低氧黄瓜幼苗根系亚精胺(Spd)、精胺(Spm)含量及(精胺+亚精胺)/腐胺的比值,显著提高ATPase活性及Ca2+、Mg2+、Fe3+、Mn2+含量.可见,EBR可调节幼苗根系多胺变化,有效提高ATPase活性,促进无机离子的吸收,缓解了低氧的伤害.     

CO2浓度升高对三种地被类观赏竹生理特性的影响

运用开顶式气室(OTCs)模拟大气CO₂浓度升高(500、700 μmol·mol^-1)情景,以环境背景大气为对照,研究CO₂浓度升高对3种地被类观赏竹(美丽箬竹、黄条金刚竹和白缟椎谷笹竹)叶片的膜脂过氧化和抗氧化系统的影响及其种间差异.结果表明: 试验进行103 d后,500 μmol·mol^-1CO₂浓度下,3种地被类观赏竹的叶片超氧阴离子含量、丙二醛(MDA)含量、相对电导率和可溶性糖含量总体上没有发生明显的变化,但叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性有一定程度的改变;700 μmol·mol^-1 CO₂浓度下,3个竹种的叶片MDA含量和相对电导率没有发生明显变化,但对叶片超氧阴离子含量、可溶性糖含量和SOD、POD、CAT、APX活性的影响较为明显.不同竹种对CO₂浓度升高环境的适应能力为美丽箬竹＞黄条金刚竹＞白缟椎谷笹竹.