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Plants have evolved a variety of defense traits against foliar herbivory, including the production of primary and secondary metabolites, the allocation of chemical compounds, and morphological plasticity. Using two vegetative generations of the invasive clonal species Alternanthera philoxeroides , we investigated the effects of maternal and offspring herbivory by Planococcus minor on the integrative defense strategy of plants. Herbivory severely inhibited leaf, stolon and root growth, as well as the production of primary metabolites (soluble sugars, starch, and total non-structural carbohydrates in stolons), and decreased average leaf area and specific leaf area of the second-generation A. philoxeroides . The changes in growth measures of the first-generation A. philoxeroides with herbivory were consistent with that of the second generation. By contrast, herbivory basically did not affect the concentration of non-structural carbohydrate compounds in the roots, and even increased the concentrations of N and total phenols in taproots. Furthermore, herbivory-induced maternal effects also reduced the growth of the second-generation plants. The results suggest that A. philoxeroides is capable of adapting to herbivory by P. minor , mainly via the allocation of available resources in belowground organs, and that the herbivory effect can persist across vegetative generations. These features may potentially improve the regeneration and tolerance of A. philoxeroides after a short-term herbivory. [ABSTRACT FROM AUTHOR]

The impact of invasive species on native biodiversity varies across environments, with invasion effects of amphibious plant species across terrestrial and aquatic systems especially poorly understood. In this study, we established 29 terrestrial plots and 23 aquatic plots which were invaded by the alien plant alligator weed, Alternanthera philoxeroides in Southern China. We measured α-species diversity (Shannon-Wiener and Simpson index), species richness and evenness, species cover and the importance value (a comprehensive index of cover, height and abundance) of A . philoxeroides in invaded communities in both aquatic and terrestrial habitats. We recorded seven environmental factors (longitude, latitude, elevation above sea level, temperature, precipitation, ammonia and nitrate) across habitats. We then used Redundancy Analysis (RDA) to determine which factors best explain A . philoxeroides invasion in either environment type. We found that terrestrial habitats had greater species diversity (Shannon index) than aquatic habitats, and the biotic resistance of aquatic plant communities to the A . philoxeroides invasion was weaker than terrestrial plant communities. Accumulated ammonia improved some indices of species diversity (Shannon-Weiner, Simpson) and evenness, but decreased species cover of A . philoxeroides in both aquatic and terrestrial environments. Precipitation increased species richness in terrestrial habitats but decreased richness in aquatic habitats. Precipitation increased A . philoxeroides cover in both environment types, while elevated nitrate increased A . philoxeroides cover in terrestrial habitats only. In aquatic habitats, species richness increased but A . philoxeroides cover decreased with increasing longitude. Our study indicates that increased precipitation may accelerate A . philoxeroides spread across aquatic and terrestrial habitats, while reducing nitrate inputs could inhibit terrestrial A . philoxeroides invasion. Aquatic communities appear to be more vulnerable to invasion by A . philoxeroides than terrestrial communities, likely due to low native species diversity. We need to intensify invasion assessment of water ecosystems in lower longitudinal regions of China and elsewhere where diversity is low. [ABSTRACT FROM AUTHOR]

Global warming could accelerate the spread of invasive species to higher latitudes and intensify their effects on native species. Here, we report results of two years of field surveys along a latitudinal gradient (21°N to 31°N) in southern China, to determine the species structure of the invasive plant Alternanthera philoxeroides community. We also performed a replacement series experiment (mono and mixed) to evaluate the effects of elevated temperature on the competitiveness of A. philoxeroides with the native co-occurring species Digitaria sanguinalis . In the field survey, we found that the dominance of A. philoxeroides increased with increasing of latitude gradient while cover of D. sanguinalis decreased. In monospecific plantings, artificial warming reduced the length of D. sanguinalis roots. In mixed plantings, warming reduced both A. philoxeroides abundance and D. sanguinalis stem length when A. philoxeroides was more prevalent in the planting. Warming also significantly reduced D. sanguinalis biomass, but increased that of A. philoxeroides. In addition, elevated temperatures significantly reduced the relative yield (RY) of D. sanguinalis , particularly when A. philoxeroides was planted in higher proportion in the plot. These results suggest that the invasiveness of A. philoxeroides increased with increasing latitude, and that warming may increase the effectiveness of its interspecific competition with D. sanguinalis . Hence, under global warming conditions, the harm to native species from A. philoxeroides would increase at higher latitudes. Our findings are critical for predicting the invasiveness of alien species under climate change. [ABSTRACT FROM AUTHOR]

Environmental heterogeneity in resource availability affects invasive plant reproductive strategies and resource allocation to reproduction. Here, we conducted two field surveys to examine the effect of wetland and terrestrial habitats on inflorescence production and resource allocation to inflorescence of the amphibious invasive plant Alternanthera philoxeroides in its invasive range (China). We also specifically examined the effects of water availability, fertilizer application, and plant density (space) in a greenhouse experiment. In field surveys, inflorescence biomass, normal monoclinous flowers and ratio of inflorescences to shoots of plants from wetlands were about 2.4-, 0.8- and 1.3-fold higher than those from terrestrial habitats, respectively. In greenhouse experiment, plants with higher fertilizer application and lower competition conditions produced more inflorescences, and had a lower ratio of roots to shoots and a comparable ratio of inflorescences to shoot and root. Furthermore, water availability had a significant interactive effect when combined with fertilizer level or plant density on inflorescence production and resource allocation. Together, our results indicate that high resources, such as those found in wetland habitats, favor both vegetative growth and sexual trait in A. philoxeroides. However, in terrestrial habitats where resources are relatively poor, the invader can adapt to the environment by allocating more resources to vegetative growth for clonal reproduction and less resources for sexual trait. This phenotypic plasticity in resource allocation likely facilitates the plant to invade heterogeneous wetlands and terrestrial environments. Unlabelled Image • Environmental heterogeneity affected resource allocation of invasive alligatorweed. • High resource availability increased resource allocation to sexual trait. • Low resource availability increased resource allocation to clonal growth. • Phenotypic plasticity in resource allocation may facilitate alligatorweed invasion. [ABSTRACT FROM AUTHOR]

• Alternanthera philoxeroides was firstly used for fermentative hydrogen production. • 60Co-γ mutagenized Enterobacter aerogenes ZJU1 was employed as inoculum. • Steam-heated acid pretreatment led to high reducing sugars from A. philoxeroides. • SEM, XRD, and FTIR revealed microstructural changes of biomass after pretreatment. • Highest biohydrogen yield of 89.8 mL/gVS was obtained using actual biomass waste. Alternanthera philoxeroides , a notorious invasive aquatic weed, is a typical lignocellulosic feedstock for fermentative biohydrogen production. To improve the dark fermentation performance, steam-heated acid pretreatment and enzymolysis were employed to release reducing sugars from A. philoxeroides , and Enterobacter aerogenes ZJU1 mutagenized by 60Co-γ irradiation was used as the inoculum. Dilute acid accompanied by steam heating significantly disrupted the fiber structures of A. philoxeroides. Scanning electron microscopic images revealed that many pores and fissures were generated in the surface of A. philoxeroides after pretreatment. X-ray diffraction and Fourier transform infrared spectroscopy analyses showed that the pretreatment facilitated the transformation of cellulose I to cellulose II in A. philoxeroides biomass, resulting in the increase of amorphous regions and the decrease of crystallinity. Under the optimum pretreatment condition (1.0 v/v% H 2 SO 4 , 135 °C for 15 min), the reducing sugar yield reached 0.354 g/g A. philoxeroides , which was further increased to 0.575 g/g A. philoxeroides after enzymolysis. The biohydrogen yield increased by 59.9% from 38.9 mL/g volatile solids (VS) of raw A. philoxeroides to 62.2 mL/gVS of the pretreated one. As compared to the wild strain, E. aerogenes ZJU1 contributed to an increase of 31.8% in the biohydrogen yield from pretreated A. philoxeroides. Further optimization of bacteria suspensions significantly increased the maximum biohydrogen production rate from 1.42 to 4.64 mL/gVS/h, advanced the biohydrogen production peak, and resulted in an increase of 42.8% in biohydrogen yield to 89.8 mL/gVS. [ABSTRACT FROM AUTHOR]