Effects of Fragmentation Intensity of Perennial Roots and Their Burial Depth on Sprouting and Early Growth of Alternanthera philoxeroides(Mart.)Griseb

[Objective] The aim was to provide theoretical basis for the prevention and control of the invasion of Alternanthera philoxeroides（Mart.）Griseb.[Method] Effects of fragmentation intensity of fresh roots and their burial depth on sprouting and early growth of A.philoxeroides were studied by control test.[Result] More sprouts of A.philoxeroides emerged when the fragmentation intensity of fresh roots was higher,while if the fragmentation intensity of fresh roots was lower,the early growth of A.philoxeroides was more rapid.The soil buried depth had significant effect on fresh root sprouts＇ emergence,but once fresh root sprouts could reach the soil surface and were given enough growth time,even if the fresh roots were buried in different depths,soil buried depth had no significant effect on its young plant growth.[Conclusion] If different fragmentation intensities of fresh roots present,there is a kind of trade-off strategy between root sprouts＇ emergence and plant＇ early growth,by which A.philoxeroides can invade new habitat successfully.To control the invasion of A.philoxeroides,it is critical to prevent its fresh root sprouts from emerging to soil surface,that is,to bury the fresh roots at a further soil depth.

Effect of Lead Stress on Growth Characteristics and Physiological Indexes of Alternanthera philoxeroides

[Objective] The paper aimed to discuss effects of different concentrations of lead stress on Alternanthera philoxeroides growth and physiological indices,to explore phytoremediation methods for removal of lead pollution. [Method] A. philoxeroides in water culture was treated with different concentration of lead,and then,its external injury was observed,its growth and physiological indexes were measured. [Result] A. philoxeroides biomass and chlorophyll content decreased; conductivity and malonaldehyde （MDA ） content were increased; the SOD,POD and CAT activities showed a trend of first increase and then decrease with increase in concentration of lead stress. [Conclusion] With increase in lead concentration,the cell membrane permeability increased and MDA had a higher accumulation,antioxidant enzymes activity decreased,the normal oxidative metabolism of A. philoxeroides was severely affected,leading it to wilt.

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.

不同水草种植模式对中华绒螯蟹扣蟹池塘 养殖性能的影响

为探究不同水草种植模式对中华绒螯蟹(Eriocheir sinensis)扣蟹池塘养殖性能的影响,本实验于2022年比较了[水花生(Alternanthera philoxeroides)单一种植、水花生和黄花水龙(Jussiaea stipulacea Ohwi)1∶1种植、黄花水龙单一种植]三种水草种植模式下扣蟹的栖息选择性、生长性能、最终养殖效果和规格分布差异情况。结果显示:(1)黄花水龙的生长速度显著快于水花生且黄花水龙中栖息扣蟹的平均体质量显著高于水花生中栖息的扣蟹,但黄花水龙中栖息扣蟹的数量明显较低;(2)在整个养殖阶段,黄花水龙组扣蟹的生长速度最快,其次为1∶1种植组,水花生组扣蟹生长速度最慢;(3)水花生组扣蟹具有成活率高、一龄性早熟率低以及残蟹率低等特点,但1∶1种植组产量最高;(4)规格分布方面,各组扣蟹体质量主要集中于6.00~8.99 g和9.00~11.99 g这两个规格区间内,黄花水龙组扣蟹在9.00~11.99 g、12.00~14.99 g和≥15 g这三个区间内的比例均高于另外两组。综上所述,在中华绒螯蟹扣蟹养殖阶段,池塘种植黄花水龙较水花生能使扣蟹的平均体质量得到提高,但是其产量以及成活率会降低,二者搭配使用可取得更高的产量。

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.

Effects of soil nitrogen levels on growth and defense of the native and introduced genotypes of alligator weed

Plants growing in nutrient-rich environment are predicted to be less defended than conspecifics under nutrient limitation.However,less is known about the effects of nutrient levels on tolerance and induced resistance,and whether the effects differ between native and introduced populations of invasive plants.We performed a greenhouse experiment with introduced(the USA)and native(Argentina)genotypes of Alternanthera philoxeroides in order to study the effects of soil nitrogen levels on plant growth,constitutive and herbivore(Agasicles hygrophila)-induced chemical defense,and herbivory tolerance.We measured total biomass,elongation rate(as proxy of growth rate),carbon and nitrogen,and the concentration of triterpenoid saponins(defensive chemicals)in leaves and roots.Constitutive resistance(+33%higher leaf triterpenoid saponins in control treatment at low nitrogen level)and tolerance[less decreased total biomass after herbivory treatment(−24%and−15%for high and low nitrogen levels)]were favored at lower nitrogen level,while induced resistance was favored at higher nitrogen level(+24%increased leaf triterpenoid saponins after herbivory treatment at high nitrogen level).Constitutive resistance and tolerance exhibited trade-offs with growth rate,while induced resistance positively correlated with growth rate.Additionally,the introduced genotypes had−6%lower content of leaf carbon in the presence of herbivores than the native genotypes at low nitrogen level,but such difference was absent at high nitrogen level.Our results indicate that soil nitrogen levels influence the preference of different defensive strategies of plant,and interweave with herbivory to determine the performance of introduced genotypes.