Occurrence and Distribution of Alternanthera philoxeroides in the Youjiang River Valley

The occurrence and distribution of Alternanthera philoxeroides in different habitats of four districts and counties in the Youjiang River Valley were investigated from September to November in 2018. The results show that A. philoxeroides certainly has occurred in watercourses, ridges, ditches, roadsides and green belts in those four districts and counties of The Youjiang valley. According to the sampling investigation, ridges have the highest frequency of occurrence, followed by ditches and roadsides. The A. philoxeroides living in ditches grows better than other four habitats, and the plants are stronger and vigorous. In the geographical division, the distribution areas of A. philoxeroides in Tianyang District and Tiandong County are the largest. Youjiang District and Pingguo County have a small amount of A. philoxeroides distributed along farmland, green belts and village houses, which has the characteristics of high local population density and strong aggregation, but the areas are smaller than other counties.

Physiological Changes and Antioxidative Mechanisms of Alternanthera philoxeroides in Phytoremediation of Cadmium

This study evaluated the physiological characteristics(e.g.,growth parameters,chlorophyll content,metabolites and antioxidative enzymes activity)of Alternanthera philoxeroides(A.philoxeroides),as a hyperaccumulator plant,during the phytoremediation of cadmium(Cd)from water.After cultivating A.philoxeroides in a Cd-containing medium for 30 days,the growth rate was inhibited by up to 33.5%as the exposed Cd concentration increased to 0.80 mmol·L−1.Cd exposure interfered with the photosynthesis of A.philoxeroides and caused oxidative stress as indicated by the rise of malondialdehyde(MDA)and H2O2,which increased by 8 times and 3 times compared to the control group.Moreover,high exposure concentrations of Cd also reduced the activities of multiple antioxidants(e.g.,GSH and AsA),indicating the inhibition of Cd on the plant’s ability to mitigate oxidative damage.Finally,the fluorescent patterns of the rhizosphere dissolved organic matter(rDOM)revealed three major components(humic,fulvic substances and protein-like substances)well correlated with the changes in antioxidant activities.Partial least-squares discriminant analysis(PLS-DA)visualized the difference in the activity of the antioxidative enzymes between different groups.The study unravelled deep insights into the potential mechanisms of tolerance and resistance of A.philoxeroides for phytoremediation of Cd pollution.

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 measuredα-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.philoxe-roides 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.

添加蚯蚓后入侵植物喜旱莲子草的生长状况

由于入侵生物自身体内的化学物质影响到土壤动物和土壤过程,试验采用土壤常见动物蚯蚓和重要入侵植物喜旱莲子草[Alternanthera philoxeroides(Mart.)Griseb.]为材料,研究蚯蚓对喜旱莲子草生理生化指标及生长的影响。结果表明,喜旱莲子草叶片中叶绿素a、叶绿素b、类胡萝卜素的含量和叶绿素总量随着添加蚯蚓数量的增加而增加;喜旱莲子草叶片淀粉和非结构性碳水化合物(NSC)的含量随着添加蚯蚓数量的增加呈递增趋势;随着添加蚯蚓数量的增加,喜旱莲子草单位面积质量和分蘖数呈上升趋势。由此可知,土壤动物蚯蚓有利于入侵植物喜旱莲子草生长。

Heavy Metal Accumulation Potential of Some Wetland Plants Growing Naturally in the City of Kolkata, India

Freshwaters are not only used locally in many developing countries but they are often over exploited for domestic purposes, agriculture and disposal of industrial wastes which result in an overload of excess nutrients, harmful chemicals and heavy metals. Plant species together with sediments and water samples collected from eleven aquatic water bodies in the vicinity of industrial units in Kolkata were studied for their potential to uptake Pb, Cd and Cr under field conditions. Cd and Cr concentrations in the sediments were higher than background values considered to be toxic. Alternanthera philoxeroides and Eichhornia crassipes were the two invasive species present, with the former being more widely distributed. Among native plants, Ipomoea aquatica was the most abundant. Metal uptake in the plants differed among species, tissues and sites. Pb and Cd accumulation in root tissues for all plants in most sites suggested an exclusion strategy for metal tolerance. Since I. aquatica is widely consumed in many parts of SE Asia, its metal content should be checked before use since it was found to efficiently translocate both Pb and Cd from roots to shoots. The potential of A. philoxeroides as a metal excluder needs to be explored further since it translocates less to its shoots as compared to E. crassipes and I. aquatica.

Effects of clonal integration and nitrogen supply on responses of a clonal plant to short-term herbivory

Aims Clonal integration,i.e.resource sharing between interconnected ramets,can help clonal plants tolerate abiotic stress.However,few studies have directly examined the ecological significance of clonal integration in the ability of clonal plants to tolerate biotic stress such as herbivory.Methods We grew clonal fragments of an invasive clonal plant Alternanthera philoxeroides,each consisting of an apical part(relatively young)and a basal part(relatively old),at two levels(low and high)of soil nitrogen(N).For each fragment,the apical part was subjected to either no herbivory or herbivory for 2 weeks by a specialist insect,Agasicles hygrophila,and was either connected with or discon-nected from the basal part not subjected to herbivory.Important Findings Herbivory in the apical part severely reduced leaf growth(leaf mass,leaf number or leaf area)and ramet production of both apical and basal parts,and increased root to shoot ratio of the apical part.Irrespective of herbivory and soil N,stem connection between the apical and the basal part decreased root to shoot ratio of the ap-ical part,but did not change its growth measures.Meanwhile,con-nection increased stem N concentration of the apical part growing under high-N supply and decreased stem carbon(C)concentration of the apical part under low-N supply.By contrast,connection in-creased root to shoot ratio of the basal part,but reduced its leaf and ramet production.Connection also increased leaf and stem C concentrations of the basal part under low-N supply.Thus,clonal integration can be beneficial for the early development of young A.philoxeroides ramets,but not for their local adaptation to herbivory damage by A.hygrophila.

土壤氮水平对喜旱莲子草原产地和引入地基因型生长和防御的影响

同种植物生长在资源丰富生境中的个体,其防御水平被认为低于生长在资源匮乏生境中的个体。然而,生境的养分水平如何影响植物的诱导抗性和耐受性,以及这种影响在入侵植物的原产地和引入地种群间是否存在差异,目前均知之甚少。本研究以入侵植物喜旱莲子草(Alternanthera philoxeroides)的原产地阿根廷和引入地美国的基因型为研究对象设计同质园实验,以探究土壤氮水平对植物的生长、组成和诱导性[莲草直胸跳甲(Agasicles hygrophila)取食诱导]化学防御以及耐受性的影响。实验中,我们测定了植物总生物量、伸长速率(生长速率的表征)以及叶片和根系中总碳、总氮和三萜皂苷(化学防御物质)的含量。研究结果显示,植物在低土壤氮水平下表现出较高的组成抗性(植物在低土壤氮水平下的叶片三萜皂苷含量高于其在高土壤氮水平的33%)和耐受性[植物被取食后总生物量下降的程度更低(植物在高土壤氮水平和低土壤氮水平下被取食后总生物量分别下降了24%和15%)],而在高土壤氮水平下表现出较高的诱导抗性(在高土壤氮水平下的植物被取食后叶片三萜皂苷含量与空白对照的植物相比升高了24%)。植物的组成抗性和耐受性与生长速率存在权衡,但诱导抗性与生长速率存在显著的正相关性。此外,引入地基因型在低土壤氮水平下叶片碳含量显著低于原产地基因型(-6%),但这种差异在高土壤氮水平下消失。这些结果表明,土壤氮水平影响植物对不同防御策略的选择偏好,并且在决定引入地基因型的表现时与植食作用存在交互作用。