Evaluation of the Impact of Alternanthera philoxeroides (Mart.) Griseb. Extract on Memory Impairment in D-Galactose-Induced Brain Aging in Mice through Its Effects on Antioxidant Enzymes, Neuroinflammation, and Telomere Shortening.

Aging is a well-known factor that accelerates brain deterioration, resulting in impaired learning and memory functions. This current study evaluated the potential of an extract of Alternanthera philoxeroides (AP), an edible flavonoid-rich plant, to ameliorate D-galactose-induced brain aging in male mice. Chronic administration of D-galactose (150 mg/kg/day) in mice mimicked the characteristics of aging by accelerating senescence via downregulation of the following telomere-regulating factors: mouse telomerase reverse transcriptase (mTERT) and mouse telomeric repeat-binding factors 1 (mTRF1) and 2 (mTRF2). D-galactose also decreased the activities of the antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD), while increasing expression of neuroinflammatory cytokines in the frontal cortex and hippocampus. Daily treatment of D-galactose-induced aging mice with AP at 250 and 500 mg/kg/day or vitamin E (100 mg/kg/day) significantly increased the activities of SOD and CAT, as well as expression of mTERT, mTRF1, and mTRF2, which are involved in telomere stabilization, but decreased the levels of proinflammatory cytokines IL-1ß, IL-6, and TNF-α. In the behavioral portion of the study, AP improved aging-related cognitive deficits in short-term memory as shown by the Y-maze task and the novel object recognition test (NORT) and long-term memory as shown by the Morris water maze test (MWMT). The flavones kaempferol-O-glucoside (1), quercetin (2), alternanthin B (3), demethyltorosaflavone D (4), and chrysoeriol-7-O-rhamnoside (5), which could be responsible for the observed effects of AP in the D-galactose-induced aging mice, were identified by HPLC analysis.

Responses of soil phosphorus cycling and bioavailability to plant invasion in river-lake ecotones.

The invasion of exotic plants in the river-lake ecotone has seriously affected the nutrient cycling processes in wetland soil. The South American species Alternanthera philoxeroides (Mart.) Griseb. is rapidly invading the river-lake ecotone in subtropical China, and has become the dominant species in the river-lake ecotone. However, there have been few studies on the effects of A. philoxeroides invasion on soil phosphorus (P) cycling and bioavailability in this ecotone. Here, we measured the bioavailable P fractions, physicochemical properties and nutrient content in the surface soils of the native plant (Zizania latifolia (Griseb.) Turcz and Nelumbo nucifera Gaertn.) communities and the adjacent invasive A. philoxeroides communities in three river-lake ecotones with different nutrient substrates in the subtropical Dongting Lake basin over a 3-year period to reveal the effects of A. philoxeroides invasion on the morphology and concentrations of soil bioavailable P. The principal coordinate analysis results showed that the A. philoxeroides invasion significantly altered the bioavailable P concentrations in the soil of native plant communities in the different river-lake ecotones, and this effect was not disturbed by the heterogeneity of the soil matrix. However, the effects of invasion into different native plant communities on the fractions of soil bioavailable P were different. Compared with native Z. latifolia and N. nucifera communities, A. philoxeroides invasion increased the concentration of inorganic P by 39.5% and 3.7%, respectively, and the concentration of organic P decreased by 32.7% and 31.9%, respectively. In addition, the invasion promoted P cycling and accumulation in the river-lake ecotone, which resulted in average decreases in the soil N:P and C:P ratios of 7.9% and 12.5%, respectively. These results highlight the impact of exotic plant invasions on nutrient cycling in wetland ecosystems in the river-lake ecotone, and this process may be detrimental to the late recovery of native plants.

Understanding the role of starch sheath layer in graviception of Alternanthera philoxeroides: a biophysical and microscopical study.

Plants' ability to sense and respond to gravity is a unique and fundamental process. When a plant organ is tilted, it adjusts its growth orientation relative to gravity direction, which is achieved by a curvature of the organ. In higher, multicellular plants, it is thought that the relative directional change of gravity is detected by starch-filled organelles that occur inside specialized cells called statocytes, and this is followed by signal conversion from physical information to physiological information within the statocytes. The classic starch statolith hypothesis, i.e., the starch accumulating amyloplasts movement along the gravity vector within gravity-sensing cells (statocytes) is the probable trigger of subsequent intracellular signaling, is widely accepted. Acharya Jagadish Chandra Bose through his pioneering research had investigated whether the fundamental reaction of geocurvature is contractile or expansive and whether the geo-sensing cells are diffusedly distributed in the organ or are present in the form of a definite layer. In this backdrop, a microscopy based experimental study was undertaken to understand the distribution pattern of the gravisensing layer, along the length (node-node) of the model plant Alternanthera philoxeroides and to study the microrheological property of the mobile starch-filled statocytes following inclination-induced graviception in the stem of the model plant. The study indicated a prominent difference in the pattern of distribution of the gravisensing layer along the length of the model plant. The study also indicated that upon changing the orientation of the plant from vertical position to horizontal position there was a characteristic change in orientation of the mobile starch granules within the statocytes. In the present study for the analysis of the microscopic images of the stem tissue cross sections, a specialized and modified microscopic illumination setup was developed in the laboratory in order to enhance the resolution and contrast of the starch granules.

Hydrophyte Debris Induced Sedimentary Phosphorus Release in Tuojiang Rivers, China.

Hydrophyte debris decomposition may contribute to phosphorus (P) release from the sediments in riverine systems, but the transport and transformation of organic phosphorus during this process has not been studied well. Here, a ubiquitous hydrophyte in southern China (Alternanthera philoxeroides, A. philoxeroides) was selected to identify the processes and mechanisms of sedimentary P release in late autumn or early spring by laboratory incubation. The results showed that the physio-chemical interactions changed quickly during the beginning of the incubation, where the redox potential and dissolved oxygen at the water-sediment interface decreased rapidly, reaching reducing (299 mV) and anoxic (0.23 mg∙L-1) conditions, respectively. Soluble reactive P, dissolved total P and total P concentrations in overlying water all increased with time from 0.011, 0.025 and 0.169 mg∙L-1 to 0.100, 0.100 and 0.342 mg∙L-1 on average, respectively. Furthermore, the decomposition of A. philoxeroides induced sedimentary organic P release to overlying water, including phosphate monoester (Mono-P), and orthophosphate diesters (Diesters-P). The proportions of Mono-P and Diesters-P were higher at 3 to 9 days than at 11 to 34 days, being 29.4% and 23.3 for Mono-P, 6.3% and 5.7% for Diesters-P, respectively. Orthophosphate (Ortho-P) increased from 63.6 to 69.7% during these timeframes, which indicated the transformations of both Mono-P and Diester-P to bio-available orthophosphate (Ortho-P), causing the rising P concentration in the overlying water. Our results revealed that hydrophyte debris decomposition in river systems might lead to autochthonous P contribution even without external P import from the watershed, accelerating the trophic state of receiving waterbodies.

Integrative Evaluation of the Ecological Hazards by Microplastics and Heavy Metals in Wetland Ecosystem.

This study was performed to evaluate the impact of microplastics and heavy metals (Pb, Cd, Cr, Cu, Zn, Ni) on sediments, water, aquatic plants (Pistia stratiotes, Alternanthera philoxeroides, and Ipomoea carnea), and fish (Labeo rohita) samples collected from five different sites in the Bajwat wetlands in Sialkot, Pakistan. The concentrations of Pb, Cd, and Cr were above the permissible limits devised by WHO in all the ecosystem components (i.e. sediments, water, plants, and fish) at all sites. The maximum amount of microplastic particles (2317 microplastic particles per kg of sediments) was recorded at Site 1. The filaments were the most commonly found type of microplastics. Plants and fish samples also showed considerable concentration of metals. The multivariate statistical analysis revealed anthropogenic sources of elevated concentrations of metal elements which could cause adverse biological effects in the ecosystem.

First Report of Fusarium proliferatum Associated with Leaf Yellow on Alternanthera philoxeroides in China.

Alternanthera philoxeroides (Mart.) Griseb is a highly invasive weed commonly found in rice fields in China. In May 2021, leaf yellowing was observed on this weed (about 10 ha) in Zhanjiang (21°19'N, 110°20'E), Guangdong Province, China. Disease incidence was approximately 20% (n = 100 investigated plants). Ten yellow leaves from 10 plants were sampled, surface-sterilized with 75% ethanol for 30 s, followed by 2% NaClO for 5 min. The leaves were rinsed three times in sterile distilled water and four sections of each leaf were placed onto potato dextrose agar (PDA). Pure cultures were obtained by transferring hyphal tips to new PDA plates. Twenty-two isolates of Fusarium ssp. (69% of the isolates) were obtained from 55% of the leaf samples. Three representative single-spore isolates (APF-1, APF-2, and APF-3) were used for further study. Colonies were white to pink on PDA. Conidiogenous cells were monophialidic or polyphialidic. Macroconidia were slightly curved, tapering apically with three to five septa, and measured from 32.5-55.8 µm × 2.5-5.1 µm in size (n=50). The morphological features of these fungi were noted to be in line with those of Fusarium proliferatum (Leslie and Summerell, 2006). For molecular identification, a colony PCR method (Lu et al. 2012) was used to amplify the internal transcribed spacer (ITS) and portions of elongation factor 1-α (EF1-α), RNA polymerase II largest subunit (RPB1), and RNA polymerase II second largest subunit (RPB2) genes using primers ITS1/ITS4, EF1-728F/EF1-986R, RPB1-R8/RPB1-F5, and RPB2-7CF/fRPB2-11aR, respectively (O'Donnell et al. 1998; O'Donnell et al. 2010). The sequences were submitted to GenBank under accession numbers MZ026797-MZ026799 (ITS) and MZ032209-MZ032217 (RPB1, RPB2, EF1-α). The sequences of the three isolates were 100% identical (ITS, 537/537 bp; RPB1, 1606/1606 bp; RPB2, 770/770 bp and EF1-α, 683/683 bp) with those of F. proliferatum (accession nos. MT378328, MN193921, MH582196, and MH582344) through BLAST analysis. Analysis of the sequences revealed a 99.87 - 100% identity with the isolates of the F. proliferatum (F. fujikuroi species complex, Asian clade) by polyphasic identification using the FUSARIUM-ID database (Yilmaz et al. 2021). The sequences were also concatenated for phylogenetic analysis by the maximum likelihood method. The isolates clustered with F. proliferatum. Pathogenicity was tested through in vivo experiments. The inoculated and control plants (n = 5, 30 days old) were sprayed with a spore suspension (1 × 105 per mL) of the three isolates individually and sterile distilled water, respectively, until run-off (Feng and Li. 2019). The test was performed three times. The plants were grown in pots in a greenhouse at 25 °C to 28 °C, with relative humidity of approximately 80%. Yellowing was observed on the inoculated plants after 7 days, while the control plants remained healthy. The pathogen re-isolated from all the inoculated plants was identical to the inoculated isolates in terms of morphology and ITS sequences. No fungi were isolated from the control plants. To the best of our knowledge, this study is the first to report F. proliferatum causing yellow symptoms on A. philoxeroides. The fungus has some potential biological control properties, but its host range needs to be further determined.

Rapid evolution of latitudinal clines in growth and defence of an invasive weed.

Re-establishment of heritable latitudinal clines in growth-related traits has been recognised as evidence for adaptive evolution in invasive plants. However, less information is known about latitudinal clines in defence and joint clinal evolution of growth and defence in invasive plants. We planted 14 native Argentinean populations and 14 introduced Chinese populations of Alternanthera philoxeroides in replicate common gardens in China. We investigated the latitudinal clines of traits related to growth and defence, and plasticity of these traits in relation to experiment site and soil nitrogen. We found that chemical defence decreased with latitude in introduced populations but increased with latitude in native populations. For growth rate, latitudinal clines were positive in introduced populations but nonexistent in native populations. There were also parallel positive latitudinal clines in total/shoot biomass and specific leaf area. Experiment site affected the occurrence or magnitude of latitudinal clines in growth rate, branch intensity and triterpenoid saponins concentration. Introduced populations were more plastic to experiment site and soil nitrogen than native populations. We provide evidence for rapid evolution of clines in growth and defence in an invasive plant. Altered herbivory gradients and trade-off between growth and defence may explain nonparallel clines between the native and introduced ranges.

Antidementia Effects of Alternanthera philoxeroides in Ovariectomized Mice Supported by NMR-Based Metabolomic Analysis.

The crude ethanol extract of the whole plant of Alternanthera philoxeroides (Mart.) Griseb was investigated for its potential as antidementia, induced by estrogen deprivation, based on in vitro antioxidant activity, ß-amyloid aggregation inhibition and cholinesterase inhibitory activity, as well as in vivo Morris water maze task (MWMT), novel object recognition task (NORT), and Y-maze task. To better understand the effect of the extract, oxidative stress-induced brain membrane damage through lipid peroxidation in the whole brain was also investigated. Additionally, expressions of neuroinflammatory cytokines (IL-1ß, IL-6 and TNF-α) and estrogen receptor-mediated facilitation genes such as PI3K and AKT mRNA in the hippocampus and frontal cortex were also evaluated. These effects were confirmed by the determination of its serum metabolites by NMR metabolomic analysis. Both the crude extract of A. philoxeroides and its flavone constituents were found to inhibit ß-amyloid (Aß) aggregation.

Comparative transcriptome analysis reveals ecological adaption of cold tolerance in northward invasion of Alternanthera philoxeroides.

BACKGROUND: Alternanthera philoxeroides (alligator weed) is a highly invasive alien plant that has continuously and successfully expanded from the tropical to the temperate regions of China via asexual reproduction. During this process, the continuous decrease in temperature has been a key limiting environmental factor. RESULTS: In this study, we provide a comprehensive analysis of the cold tolerance of alligator weed via transcriptomics. The transcriptomic differences between the southernmost population and the northernmost population of China were compared at different time points of cold treatments. GO enrichment and KEGG pathway analyses showed that the alligator weed transcriptional response to cold stress is associated with genes encoding protein kinases, transcription factors, plant-pathogen interactions, plant hormone signal transduction and metabolic processes. Although members of the same gene family were often expressed in both populations, the levels of gene expression between them varied. Further ChIP experiments indicated that histone epigenetic modification changes at the candidate transcription factor gene loci are accompanied by differences in gene expression in response to cold, without variation in the coding sequences of these genes in these two populations. These results suggest that histone changes may contribute to the cold-responsive gene expression divergence between these two populations to provide the most beneficial response to chilling stimuli. CONCLUSION: We demonstrated that the major alterations in gene expression levels belonging to the main cold-resistance response processes may be responsible for the divergence in the cold resistance of these two populations. During this process, histone modifications in cold-responsive genes have the potential to drive the major alterations in cold adaption necessary for the northward expansion of alligator weed.

Soil resource heterogeneity competitively favors an invasive clonal plant over a native one.

Soil resource heterogeneity can affect plant growth and competitive ability. However, little is known about how soil resource heterogeneity affects competitive interactions between invasive and native plants. We conducted an experiment with an invasive clonal plant Alternanthera philoxeroides and a coexisting native one Alternanthera sessilis. The experiment was a randomized design with three factors, i.e. two species (A. philoxeroides and A. sessilis), two interspecific competition treatments (with and without) and five soil treatments (three homogeneous treatments and two small-scale heterogeneous treatments consisting of two patches of 10 cm × 15 cm and with different initial planting positions). Irrespective of competition, increasing soil resource availability increased the growth of A. philoxeroides. Increasing soil resource availability also increased the growth of A. sessilis without competition, but had no impact with competition. Irrespective of competition, soil resource heterogeneity increased biomass and ramet production of A. philoxeroides, and such effects were independent of initial planting position. For A. sessilis, however, soil resource heterogeneity only increased ramet production when the initial plant was grown in the low-resource patch without competition. Our results suggest that both high soil resource availability and small-scale soil resource heterogeneity can increase the relative competitive ability of the invasive plant A. philoxeroides when grown with its native congener A. sessilis. These findings may partly explain the invasion success of this clonal species in area with high soil resource availability and heterogeneity caused by e.g. nitrogen deposition, fertilization and disturbance.

Herbivory may promote a non-native plant invasion at low but not high latitudes.

BACKGROUND AND AIMS: The strengths of biotic interactions such as herbivory are expected to decrease with increasing latitude for native species. To what extent this applies to invasive species and what the consequences of this variation are for competition among native and invasive species remain unexplored. Here, herbivore impacts on the invasive plant Alternanthera philoxeroides and its competition with the native congener A. sessilis were estimated across latitudes in China. METHODS: An common garden experiment spanning ten latitudinal degrees was conducted to test how herbivore impacts on A. philoxeroides and A. sessilis, and competition between them change with latitude. In addition, a field survey was conducted from 21°N to 36.8°N to test whether A. philoxeroides invasiveness changes with latitude in nature as a result of variations in herbivory. KEY RESULTS: In the experiment, A. sessilis cover was significantly higher than A. philoxeroides cover when they competed in the absence of herbivores, but otherwise their cover was comparable at low latitude. However, A. philoxeroides cover was always higher on average than A. sessilis cover at middle latitude. At high latitude, only A. sessilis emerged in the second year. Herbivore abundance decreased with latitude and A. philoxeroides emerged earlier than A. sessilis at middle latitude. In the field survey, the ratio of A. philoxeroides to A. sessilis cover was hump shaped with latitude. CONCLUSION: These results indicate that herbivory may promote A. philoxeroides invasion only at low latitude by altering the outcome of competition in favour of the invader and point to the importance of other factors, such as earlier emergence, in A. philoxeroides invasion at higher latitudes. These results suggest that the key factors promoting plant invasions might change with latitude, highlighting the importance of teasing apart the roles of multiple factors in plant invasions within a biogeographic framework.

Selenium enhanced phytoremediation of diesel contaminated soil by Alternanthera philoxeroides.

Using a 60-day pot culture experiment, we investigated the effect of selenium on phytoremediation of soil containing high-level diesel by Alternanthera philoxeroides (alligator weed). Diesel (20 g kg-1) decreased the growth of A. philoxeroides and induced oxidative stress, as indicated by tissue levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA). Adding Se (0.5 or 1.5 mg kg-1) to diesel-treated soil alleviated oxidative stress and improved biomass production, and the low dose was as effective as the high dose. After 60 days, the reduction in rhizospheric soil diesel was 20.1 ±â€¯0.55% without Se and 35.2 ±â€¯3.6% with Se, showing a significant increase in efficiency. Again, the low Se dose was as effective as the high dose. These findings advance the field phytoremediation by demonstrating that Se, at 0.5 mg kg-1, enhances removal and increases plant tolerance to petroleum hydrocarbons.

Physiological Analysis and Proteome Quantification of Alligator Weed Stems in Response to Potassium Deficiency Stress.

The macronutrient potassium is essential to plant growth, development and stress response. Alligator weed (Alternanthera philoxeroides) has a high tolerance to potassium deficiency (LK) stress. The stem is the primary organ responsible for transporting molecules from the underground root system to the aboveground parts of the plant. However, proteomic changes in response to LK stress are largely unknown in alligator weed stems. In this study, we investigated the physiological and proteomic changes in alligator weed stems under LK stress. First, the chlorophyll and soluble protein content and SOD and POD activity were significantly altered after 15 days of LK treatment. The quantitative proteomic analysis suggested that a total of 296 proteins were differentially abundant proteins (DAPs). The functional annotation analysis revealed that LK stress elicited complex proteomic alterations that were involved in oxidative phosphorylation, plant-pathogen interactions, glycolysis/gluconeogenesis, sugar metabolism, and transport in stems. The subcellular locations analysis suggested 104 proteins showed chloroplastic localization, 81 proteins showed cytoplasmic localization and 40 showed nuclear localization. The protein⁻protein interaction analysis revealed that 56 proteins were involved in the interaction network, including 9 proteins involved in the ribosome network and 9 in the oxidative phosphorylation network. Additionally, the expressed changes of 5 DAPs were similar between the proteomic quantification analysis and the PRM-MS analysis, and the expression levels of eight genes that encode DAPs were further verified using an RT-qPCR analysis. These results provide valuable information on the adaptive mechanisms in alligator weed stems under LK stress and facilitate the development of efficient strategies for genetically engineering potassium-tolerant crops.

Detection and epidemic dynamic of ToCV and CCYV with Bemisia tabaci and weed in Hainan of China.

BACKGROUND: In recent years, two of the crinivirus, Tomato chlorosis virus (ToCV) and Cucurbit chlorotic yellows virus (CCYV) have gained increasing attention due to their rapid spread and devastating impacts on vegetable production worldwide. Both of these viruses are transmitted by the sweet potato whitefly, Bemisia tabaci (Gennadius), in a semi-persistent manner. Up to now, there is still lack of report in Hainan, the south of China. METHODS: We used observational and experimental methods to explore the prevalence and incidence dynamic of CCYV and ToCV transmitted by whiteflies in Hainan of China. RESULTS: In 2016, the chlorosis symptom was observed in the tomato and cucumber plants with a large number of B. tabaci on the infected leaves in Hainan, China, with the incidence rate of 69.8% and 62.6% on tomato and cucumber, respectively. Based on molecular identification, Q biotype was determined with a viruliferous rate of 65.0% and 55.0% on the tomato and cucumber plants, respectively. The weed, Alternanthera philoxeroides near the tomato and cucumber was co-infected by the two viruses. Furthermore, incidence dynamic of ToCV and CCYV showed a close relationship with the weed, Alternanthera philoxeroides, which is widely distributed in Hainan. CONCLUSION: Our results firstly reveal that the weed, A. philoxeroides is infected by both ToCV and CCYV. Besides, whiteflies showed a high viruliferous rate of ToCV and CCYV. Hainan is an extremely important vegetable production and seed breeding center in China. If the whitefly can carry these two viruses concurrently, co-infection in their mutual host plants can lead to devastating losses in the near future.

Oxygen absorption by adventitious roots promotes the survival of completely submerged terrestrial plants.

Background and Aims Flooding imposes stress upon terrestrial plants because it results in oxygen deficiency, which is considered a major problem for submerged plants. A common response of terrestrial plants to flooding is the formation of aquatic adventitious roots. Some studies have shown that adventitious roots on submerged plants are capable of absorbing water and nutrients. However, there is no experimental evidence for the possible oxygen uptake function of adventitious roots or for how important this function might be for the survival of plants during prolonged submergence. This study aims to investigate whether adventitious roots absorb oxygen from the water column, and whether this new function is beneficial to the survival of completely submerged plants. Methods Taking Alternanthera philoxeroides (Mart.) Griseb. as a representative species, the profiling of the underwater oxygen gradient towards living and dead adventitious roots on completely submerged plants was conducted, the oxygen concentration in stem nodes with and without adventitious roots was measured, and the growth, survival and non-structural carbohydrate content of completely submerged plants with and without adventitious roots was investigated. Key Results Oxygen profiles in the water column of adventitious roots showed that adventitious roots absorbed oxygen from water. It is found that the oxygen concentration in stem nodes having adventitious roots was higher than that in stem nodes without adventitious roots, which implies that the oxygen absorbed by adventitious roots from water was subsequently transported from the roots to other plant tissues. Compared with plants whose adventitious roots had been pruned, those with intact adventitious roots had slower leaf shedding, slower plant mass reduction, more efficient carbohydrate economy and prolonged survival when completely submerged. Conclusions The adventitious roots of A. philoxeroides formed upon submergence can absorb oxygen from ambient water, thereby alleviating the adverse effects of oxygen deficiency, enabling efficient utilization of carbohydrates and delaying the death of completely submerged plants.

New Anti-HBV C-Boivinopyranosyl Flavones from Alternanthera philoxeroides.

C-boivinopyranosyl flavones have rarely been isolated from nature. In the search for anti-HBV (hepatitis b virus) constituents of Alternanthera philoxeroides, two new compounds, luteolin-6-C-ß-D-boivinopyranosyl-3'-O-ß-D-glucopyranoside (1) and chrysoeriol-6-C-ß-D-boivinopyranosyl-4'-O-ß-D-glucopyranoside (2), along with three known C-boivinopyranosyl flavones (compounds 3-5) were isolated. Their structures were determined by spectroscopic analyses including 1D and 2D NMR, HR-ESI-MS, IR spectra. Compounds 1, 2 and 3 showed significant anti-HBV activities through specifically inhibiting the secretion of HBsAg in HepG2.2.15.

Shifting effects of physiological integration on performance of a clonal plant during submergence and de-submergence.

BACKGROUND AND AIMS: Submergence and de-submergence are common phenomena encountered by riparian plants due to water level fluctuations, but little is known about the role of physiological integration in clonal plants (resource sharing between interconnected ramets) in their adaptation to such events. Using Alternanthera philoxeroides (alligator weed) as an example, this study tested the hypotheses that physiological integration will improve growth and photosynthetic capacity of submerged ramets during submergence and will promote their recovery following de-submergence. METHODS: Connected clones of A. philoxeroides, each consisting of two ramet systems and a stolon internode connecting them, were grown under control (both ramet systems untreated), half-submerged (one ramet system submerged and the other not submerged), fully submerged (both ramet systems submerged), half-shaded (one ramet system shaded and the other not shaded) and full-shaded (both ramet systems shaded) conditions for 30 d and then de-submerged/de-shaded for 20 d. The submerged plants were also shaded to very low light intensities, mimicking typical conditions in turbid floodwater. KEY RESULTS: After 30 d of submergence, connections between submerged and non-submerged ramets significantly increased growth and carbohydrate accumulation of the submerged ramets, but decreased the growth of the non-submerged ramets. After 20 d of de-submergence, connections did not significantly affect the growth of either de-submerged or non-submerged ramets, but de-submerged ramets had high soluble sugar concentrations, suggesting high metabolic activities. The shift from significant effects of integration on both submerged and non-submerged ramets during the submergence period to little effect during the de-submergence period was due to the quick recovery of growth and photosynthesis. The effects of physiological integration were not found to be any stronger under submergence/de-submergence than under shading/de-shading. CONCLUSIONS: The results indicate that it is not just the beneficial effects of physiological integration that are crucial to the survival of riparian clonal plants during periods of submergence, but also the ability to recover growth and photosynthesis rapidly after de-submergence, which thus allows them to spread.

Heterologous expression of an alligatorweed high-affinity potassium transporter gene enhances salinity tolerance in Arabidopsis thaliana.

UNLABELLED: • PREMISE OF THE STUDY: The potassium cation (K(+)), one of the most abundant cations in cells, improves plant tolerance to various abiotic stresses. Alligatorweed (Alternanthera philoxeroides) is well known for its strong capacity to accumulate K(+) The distinctive K(+) accumulation capability of alligatorweed is linked to a high-affinity K(+) transport facilitated by K(+)-uptake transporters (ApKUPs).• METHODS: A putative K(+) transporter gene, ApKUP4, was isolated from alligatorweed using degenerate primers and rapid amplification of cDNA ends (RACE) techniques. Gene expression profiles were performed by quantitative real time PCR and northern blot analysis. Moreover, we introduced ApKUP4 into Arabidopsis to determine its function in improving crop nutrition and NaCl stress tolerance.• KEY RESULTS: ApKUP4 was localized throughout the entire alligatorweed plant, and its expression was stimulated in the stems and roots under K(+) deficiency, osmotic stress, and salinity stress. Northern blot analysis revealed that ApKUP4 was present in all tested organs of transgenic Arabidopsis plants. Compared with the wild type, Arabidopsis plants overexpressing ApKUP4 showed improved growth and K(+) homeostasis. Moreover, ApKUP4 overexpression in Arabidopsis plants enhanced plant tolerance to salinity stress, as evidenced by reduced water loss and ROS generation, associated with enhanced photosynthesis, nutritional status, and enzymatic antioxidants.• CONCLUSIONS: The present study provides direct evidence that the alligatorweed K(+) transporter gene, ApKUP4, contributes to salinity tolerance in transgenic Arabidopsis seedlings, demonstrating the essentiality of potassium homeostasis for plant salinity tolerance.

Effects of periodic heat events on the reproduction and longevity of female and male Agasicles hygrophila (Coleoptera: Chrysomelidae).

Alternanthera philoxeroides (Amaranthaceae), commonly known as alligator weed, is a globally invasive and detrimental perennial weed. Agasicles hygrophila serves as an important biocontrol agent for alligator weeds. However, during mid-summer, when temperatures increase, A. hygrophila populations experience a significant decline, leading to ineffective weed control. This study has examined the impact of periodic heat events on the reproduction and survival of A. hygrophila females and males using various mating combinations and durations of temperature treatments. The results demonstrated significant effects on all of the studied parameters across mating combinations when compared with the control. Under the same temperature combination, the fecundity and survival rates of females, as well as the egg-hatching rate, decreased significantly with increasing repeated heat exposure. Furthermore, the egg-hatching rate varied significantly among different temperatures and time-interval combinations. In addition, the females displayed greater sensitivity to heat stress than males in terms of fecundity. These findings enhance our understanding of A. hygrophila population dynamics during summer and provide insights into the release of biocontrol agents in diverse regions with varying climates.

Impacts of Soil Properties on Species Diversity and Structure in Alternanthera philoxeroides-Invaded and Native Plant Communities.

Soil properties can affect plant population dynamics and the coexistence of native and invasive plants, thus potentially affecting community structure and invasion trends. However, the different impacts of soil physicochemical properties on species diversity and structure in native and invaded plant communities remain unclear. In this study, we established a total of 30 Alternanthera philoxeroides-invaded plots and 30 control plots in an area at the geographical boundary between North and South China. We compared the differences in species composition between the invaded and native plant communities, and we then used the methods of regression analysis, redundancy analysis (RDA), and canonical correspondence analysis (CCA) to examine the impacts of soil physicochemical properties on four α-diversity indices and the species distribution of these two types of communities. We found that A. philoxeroides invasion increased the difference between the importance values of dominant plant species, and the invasion coverage had a negative relationship with the soil-available potassium (R2 = 0.135; p = 0.046) and Patrick richness index (R2 = 0.322; p < 0.001). In the native communities, the species diversity was determined with soil chemical properties, the Patrick richness index, the Simpson dominance index, and the Shannon-Wiener diversity index, which all decreased with the increase in soil pH value, available potassium, organic matter, and ammonium nitrogen. However, in the invaded communities, the species diversity was determined by soil physical properties; the Pielou evenness index increased with increasing non-capillary porosity but decreased with increasing capillary porosity. The determinants of species distribution in the native communities were soil porosity and nitrate nitrogen, while the determinants in the invaded communities were soil bulk density and available potassium. In addition, compared with the native communities, the clustering degree of species distribution in the invaded communities intensified. Our study indicates that species diversity and distribution have significant heterogeneous responses to soil physicochemical properties between A. philoxeroides-invaded and native plant communities. Thus, we need to intensify the monitoring of soil properties in invaded habitats and conduct biotic replacement strategies based on the heterogeneous responses of native and invaded communities to effectively prevent the biotic homogenization that is caused by plant invasions under environmental changes.