Invasive Lespedeza cuneata and native Lespedeza virginica experience asymmetrical benefits from rhizobial symbionts

Background and Aims

Lespedeza cuneata (Dum. Cours.) G. Don is an invasive legume that displaces populations of native N. American congeners. Our aims are to determine the growth benefits of different rhizobacterial strains for L. cuneata and native Lespedeza virginica (L.) Britton, and to determine if these strains influence competition between these plants.

Methods

Plants were grown under nitrogen-limiting conditions in sterilized soil in pairs consisting of two L. cuneata, two L. virginica, or one of each species, and then plants were inoculated with one of seven rhizobial isolates, or with a no-strain control. After 3 months, plants were harvested for determination of biomass and nodulation rate.

Results

Five of the assayed stains improved L. cuneata biomass over uninoculated controls, but none of the strains benefited L. virginica. L. cuneata plants had more biomass and root nodules when grown in competition with L. virginica than with a conspecific.

Conclusions

Asymmetrical benefits from these symbionts accrued to invasive L. cuneata but not to native L. virginica, and this may provide the invader with a growth advantage in the field. Changes in the availability of effective symbionts in the soils of invaded sites can shape performance of native and invasive plants.     

Chemical constituents from Lespedeza cuneata G. Don (Leguminosae)

Phytochemical investigation of Lespedeza cuneata led to the isolation of seventeen compounds including three steroids (β-sitosterol 1, β-sitosterol-6′-linolenoyl-3-O-β-d-glucopyranoside 3, and β-sitosterol glucoside 13), nine flavonoids (quercetin 4, kaempferol 5, isovitexin 8, hirsutrin 9, nicotiflorin 10, vitexin 11, astragalin 12, trifolin 14, and isorhamnetin 17), two phenolics (benzyl-β-d-glucopyranoside 7 and homovanillyl alcohol 16), one carotenoid (loroxanthin 2), one lignin (7R,8S–dihydrodehydrodiconiferyl alcohol 15), and one hexose (pinitol 6) on the basis of their spectroscopic data. Among these compounds, 2, 3, 7, 15 and 16 were reported for the first time from the genus Lespedeza. The taxonomic significance of these isolated compounds was also summarized.     

Intraspecific seed interactions alter seedling emergence of Lespedeza cuneata under field conditions

There is growing recognition that seeds influence one another prior to, or shortly after, germination. Both interspecific and intraspecific seed–seed interactions have been reported, but for the latter, the evidence is almost exclusively from laboratory and greenhouse studies so that it is unclear whether such intraspecific seed interactions occur under field conditions. We tested how Lespedeza cuneata seed density influenced seedling emergence within a native grassland located in Kansas, USA and whether this response was related to seed leachate. The percentage of L. cuneata seedlings that emerged under field conditions was negatively related to seed density. After confirming this pattern in the greenhouse, we found that at low seed densities, addition of seed leachate had similar effects on seedling emergence as high seed densities in the absence of leachate. Our results provide some of the best evidence to date, that intraspecific seed density can influence seedling emergence in the field and that these effects are likely linked to seed leachate.     

Developmental Differences in the Location of Polyphenols and Condensed Tannins in Leaves and Stems of Sericea Lespedeza, Lespedeza cuneata

This histologkal study was performed to determine whether differencesin location and concentration of polyphenols and condensed tanninscould be observed in leaves and stems of sericea lespedeza genotypesof high (HP) or low (LP) phenolic content. Polyphenols and condensedtannins were especially evident in the vacuoles of paraveinalmesophyll cells from leaves of both genotypes. However, higherlevels of these substances were observed in paraveinal cellsof HP leaves. Cross-sections through young stem internodes revealedmany perivascular and vascular parenchyma cells staining prominentlyfor polyphenols in both genotypes. Their location in vacuolesof paraveinal mesophyll cells that function in photosynthatetransport within the leaf suggests that these substances playan active role in physiological processes of sericea lespedezaplants. Alternatively, they could represent a form in whichthese plants store excess photosynthates. Lespedeza cuneata (Dumont de Courset) G. Don, sericea lespedeza, polyphenols, condensed tannins, leaf anatomy, stem anatomy     

Nucleosomes facilitate their own invasion

DNA wrapped in nucleosomes is sterically occluded, creating obstacles for polymerase, regulatory, remodeling, repair and recombination complexes, which require access to the wrapped DNA. How such complexes recognize and gain access to their DNA target sites is not known. Here we report the direct detection of a dynamic equilibrium conformational transition in nucleosomes that greatly increases the distance between the end of the nucleosomal DNA and the histone core. We quantified the equilibrium constant for this transition under physiological conditions. As predicted by these findings, addition of LexA protein to nucleosomes containing the LexA target site drives this conformational equilibrium toward the unwrapped, accessible state, simultaneously allowing stable LexA binding. This inherent property of nucleosomes allows any protein, whether an energy-dependent machine or a passive binder, to gain access even to buried stretches of nucleosomal DNA.     

铁扫帚中总多糖提取工艺的研究

研究了铁扫帚中总多糖提取的最佳工艺,并对其进行了薄层层析,结果表明:A3B2C1条件下,总多糖提取率最高。薄层层析得两个组分,其Rf值分别为:0.65和0.55     

Effect of feeding sericea lespedeza (Lespedeza cuneata) on growth performance,blood metabolites,and carcass characteristics of Kiko crossbred male kids

Twenty-four high percentage Kiko crossbred male kids (body weight (BW), 27.8 ± 2.2 kg) were stratified by BW and randomly allocated to one of four experimental treatment groups (n = 6). Diets contained different levels of the condensed tannin (CT) containing forage sericea lespedeza (SL, Lespedeza cuneata) dried meal replacing alfalfa (Medicago sativa) pellets (ALF). Experimental treatments included: the control diet – 0% SL and 30% ALF; 10% SL and 20% ALF; 20% SL and 10% ALF; or 30% SL and 0% ALF as fed. Sericea lespedeza whole plant dried meal, incorporated in the grain mix portion of the diet and the mix was fed daily at 70% of total feed offered, with the remaining 30% consisting of bermudagrass (Cynodon doctylon) hay (BGH). Animals were fed once a day and the intake was adjusted every 3–4 days so that a 4–6% was refused (grain mix/SL and hay). Body weights were taken at the beginning, mid, and end of the study and blood was collected twice, at the beginning and at the end of the study, for complete analysis. The performance period lasted 63 days and at the completion of the study, goats were harvested and carcass characteristics measured. There was no difference in initial or final BW of goats; however, average daily gain (ADG) was higher (quadratic, P = 0.01) in goats consuming either all ALF or SL diets. Average daily dry matter (DM) and CT intake increased (linear, P = 0.04 and P < 0.0001, respectively) as the level of SL increased in the diet; however, body weight gain:feed (G:F, kg/kg dry matter) was lower for 10 or 20% SL diets (quadratic, P = 0.002). Scrotal circumference tended to decrease (quadratic, P = 0.07) in goats fed 10 or 20% SL and height at withers decreased (linear, P = 0.05) with addition of SL. Adjusted body fat thickness decreased (linear, P = 0.02) with added SL. Dressing percentages were low and ranged from 37.6 to 39.1 ± 1.5 for all diets. White blood cells decreased (linear, P = 0.05) and lymphocytes % increased (linear, P = 0.05) with added SL. Serum creatinine kinase and alanine aminotransferase increased (linear, P = 0.01 and P = 0.001, respectively) and serum amylase decreased (linear, P = 0.01) as the level of SL increased. In conclusion, addition of SL up to 30% or CT up to 22.2 mg/kg DM in the diet did not adversely affect growth performance of goats, and it produced lower fat in the carcass.     

High propagule production and reproductive fitness homeostasis contribute to the invasiveness of Lespedeza cuneata (Fabaceae)

Comparative studies of congeneric native and exotic species have proved fruitful in understanding plant traits that foster invasion. Using this approach, we investigate the complex reproductive system of the invasive Lespedeza cuneata (Dum.-Cours.) G. Don in relation to three native congeners in the variable environment of the North American tallgrass prairie. Lespedeza species produce both chasmogamous (CH) and cleistogamous (CL) flowers, and propagate clonally via vegetative buds. Utilizing multiple natural populations over 2 years, we investigated reproductive modes of individuals from bagged and unbagged treatments of each species. We found that L. cuneata produced a mean of five times as many seeds and a significantly greater number of vegetative buds than any native studied, and over twenty times as many CH flowers. Insect visitation significantly affected seed set in CH flowers, though some autonomous CH selfing occurred in all species. The invasive relied relatively less on selfing than the natives and exhibited less variation in reproductive output from both modes of reproduction. We conclude that the diverse reproductive biology and wide regeneration niche of L. cuneata in relation to its native congeners confer a fitness homeostasis that facilitates the successful spread of this invasive under a wide range of conditions.     

Plant community recovery following Sericea lespedeza (Lespedeza cuneata) removal: testing for a soil legacy effect

Restoration of plant communities can be hindered by the legacy of previously established invaders, despite their physical removal from the community. Current evidence, mainly built on short‐term greenhouse experiments, suggests that Sericea lespedeza (Lespedeza cuneata) invasion not only suppresses native plant species, but also alters soil conditions in host communities. As a result, L. cuneata may create a soil legacy that impedes plant community restoration. We examined the response of a Kansas grassland following L. cuneata removal to determine if historical L. cuneata abundance affected (1) plant community composition and (2) the establishment of additional native species. To address these questions, L. cuneata seeds were sown into 300 plots at a wide range of densities under different combinations of simulated disturbance and soil fertilization. After a three‐year establishment period, L. cuneata was removed from the community, and 13 native forb species were sown into all plots. Over 4 years, we found little evidence for a soil legacy effect that influenced community response post‐removal. Although there was a detectable relationship between community composition and L. cuneata, the variation explained by this relationship was very low. Similarly, the establishment of sown native species was unrelated to the historical abundance of L. cuneata. These results indicate that, regardless of initial density, L. cuneata does not impede plant community recovery in this system if effectively controlled within the first 3 years of invasion, and legacy effects inferred from greenhouse experiments may not translate to impacts on the plant community in the field.     

Affinity purification and characterization of a key enzyme responsible for circadian rhythmic control of nyctinasty in Lespedeza cuneata L

The synthesis of an affinity gel aimed at leaf-opening factor beta-glucosidase (LOFG) and affinity purification of LOFG is presented. A gluconamidine-based beta-glucosidase inhibitor was used as the ligand of the affinity gel. beta-Glucosidase exhibiting an activity shift throughout the day was selectively purified from Lespedeza cuneata Don by the affinity gel. The resulting LOFG exhibited high substrate specificity toward the leaf-opening factor.     

Phosphorus enhances Al resistance in Al-resistant Lespedeza bicolor but not in Al-sensitive L. cuneata under relatively high Al stress

Background and Aims

Aluminium (Al) toxicity and phosphorus (P) deficiency often co-exist in acidic soils and limit crop production worldwide. Lespedeza bicolor is a leguminous forage species that grows very well in infertile, acidic soils. The objective of this study was to investigate the effects of Al and P interactions on growth of Lespedeza and the distributions of Al and P in two different Al-resistant species, and to explore whether P can ameliorate the toxic effect of Al in the two species.

Methods

Two species, Lespedeza bicolor and L. cuneata, were grown for 30 d with alternate Al and P treatments in a hydroponics system. Harvested roots were examined using a root-system scanner, and the contents of Al, P and other nutrient elements in the plants were determined using inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Haematoxylin staining was used to observe the distribution of Al in the roots of seedlings. After pre-culture with or without P application, organic acids in the exudates of roots exposed to Al were held in an anion-exchange resin, eluted with 2 m HCl and then analysed using high-performance liquid chromatography (HPLC).

Key Results

Lespedeza bicolor exhibited a stronger Al resistance than did L. cuneata; Al exclusion mechanisms may mainly be responsible for resistance. P application alleviated the toxic effect of Al on root growth in L. bicolor, while no obvious effects were observed in L. cuneata. Much less Al was accumulated in roots of L. bicolor than in L. cuneata after P application, and the P contents in both roots and shoots increased much more for L. bicolor than for L. cuneata. Lespedeza bicolor showed a higher P/Al ratio in roots and shoots than did L. cuneata. P application decreased the Al accumulation in root tips of L. bicolor but not in L. cuneata. The amount of Al-induced organic acid (citrate and malate) exudation from roots pre-cultured with P was much less than from roots without P application; no malate and citrate exudation was detected in L. cuneata.

Conclusions

P enhanced Al resistance in the Al-resistant L. bicolor species but not in the Al-sensitive L. cuneata under relatively high Al stress, although P in L. cuneata might also possess an alleviative potential. Enhancement of Al resistance by P in the resistant species might be associated with its more efficient P accumulation and translocation to shoots and greater Al exclusion from root tips after P application, but not with an increased exudation of organic acids from roots.Key words: Lespedeza bicolor, L. cuneata, Al toxicity, Al resistance, root morphology, phosphorus     

Comparison of the herbivore defense and competitive ability of ancestral and modern genotypes of an invasive plant,Lespedeza cuneata

The evolution of increased competitive ability (EICA) hypothesis provides a compelling explanation for the success of invasive species. It contends that because alien plants have escaped their coevolved natural enemies, selection pressures favor a diversion of resources from herbivore defense to traits that confer increased competitive ability. Here, we provide evidence for EICA in the noxious grassland invader Lespedeza cuneata, by comparing the ancestral genotype introduced to North America in 1930 with modern‐day invasive (North American) and native (Japanese) genotypes. We found that the invasive genotype was a better competitor than either the native or the ancestral genotype. Further, the invasive genotype exhibited greater induced resistance but lower constitutive resistance than the ancestral and native genotypes. Our results suggest that selection has played a pivotal role in shaping this invasive plant species into a more aggressive, but less constitutively defended competitor.     

紫茎泽兰入侵对土壤细菌的群落组成和多样性的影响

外来生物入侵可能对生物群落结构和生态系统功能产生多种影响, 但入侵植物与土壤微生物群落组成和多样性的关系尚不清楚。为了揭示外来植物紫茎泽兰(Eupatorium adenophorum)入侵对土壤化学性质和细菌群落组成及多样性的影响, 本研究利用第二代高通量测序技术, 比较了紫茎泽兰不同入侵程度的生境(本地植物群落、紫茎泽兰与本地植物混生群落、紫茎泽兰单优群落)土壤中细菌群落的差异。土壤化学性质分析表明, 土壤pH值、有机质、全N和全K随着紫茎泽兰的入侵而逐渐降低, 而土壤全P则在入侵程度最高的生境土壤中最高。通过测序共获得7,755个细菌OUT (operational taxonomic unit)。结果表明, 紫茎泽兰入侵对土壤的细菌多样性影响较小, ACE和Chao指数在3种不同生境间的差异不显著。细菌在紫茎泽兰与本地植物混生群落中的Shannon指数最低, 即细菌的多样性在中等入侵程度的生境最低。此外, 紫茎泽兰入侵改变了土壤细菌组成和结构, 酸杆菌门(Acidobacteria)和疣微菌门(Verrucomicrobia)的相对丰度, 从本地植物群落、混合群落到紫茎泽兰单优群落, 呈现出先增加后减少的趋势。可见, 紫茎泽兰入侵一定程度上改变了土壤微生物的多样性和群落结构, 并改变了土壤的化学性质。     

Plant invasion alters trait composition and diversity across habitats

Increased globalization has accelerated the movement of species around the world. Many of these nonnative species have the potential to profoundly alter ecosystems. The mechanisms underpinning this impact are often poorly understood, and traits are often overlooked when trying to understand and predict the impacts of species invasions on communities. We conducted an observational field experiment in Canada's first National Urban Park, where we collected trait data for seven different functional traits (height, stem width, specific leaf area, leaf percent nitrogen, and leaf percent carbon) across an abundance gradient of the invasive Vincetoxicum rossicum in open meadow and understory habitats. We assessed invasion impacts on communities, and associated mechanisms, by examining three complementary functional trait measures: community‐weighted mean, range of trait values, and species’ distances to the invader in trait space. We found that V. rossicum invasion significantly altered the functional structure of herbaceous plant communities. In both habitats V. rossicum changed the community‐weighted means, causing invaded communities to become increasingly similar in their functional structure. In addition, V. rossicum also reduced the trait ranges for a majority of traits indicating that species are being deterministically excluded in invaded communities. Further, we observed different trends in the meadow and understory habitats: In the understory, resident species that were more similar to V. rossicum in multivariate trait space were excluded more, however this was not the case in the meadow habitat. This suggests that V. rossicum alters communities uniquely in each habitat, in part by creating a filter in which only certain resident species are able to persist. This filtering process causes a nonrandom reduction in species' abundances, which in turn would be expected to alter how the invaded ecosystems function. Using trait‐based frameworks leads to better understanding and prediction of invasion impacts. This novel framework can also be used in restoration practices to understand how invasion impacts communities and to reassemble communities after invasive species management.     

Biological invasion alters regional nitrogen-oxide emissions from tropical rainforests

We explored whether the invasion of an exotic, nitrogen (N) fixing tree into native Hawaiian tropical forests has altered regional emissions of nitrous oxide (N₂O) and nitric oxide (NO), two atmospherically important trace gases produced by microorganisms in soils. Ecosystem processes, including nitrification and N-oxide emissions, were not affected by Morella faya (formerly Myrica faya ) invasion until it dominated the community with few native species in the overstory or understory. Remote-sensing estimates of upper-canopy leaf N concentration were strongly correlated to N-oxide emissions in ecosystems at the mesic-wet end of a precipitation gradient, where temperatures are warm, relatively constant, and N limits biological processes. In contrast, remotely sensed and field-based canopy chemistry was not related to N-oxide emissions in dry forest ecosystems where the seasonality of temperature and moisture exerted stronger control over soil gas fluxes. Thus, remote sensing of canopy N was useful for estimating the impact of M. faya on regional N-oxide emissions only in regions receiving >1800 mm rainfall annually. Our estimates of N-oxide emissions from M. faya are half as large and 35 times more precise than those made using traditional, plot-level methods of extrapolation. Over the 40 years since its first occurrence in wet forests of Hawai'i Volcanoes National Park, M. faya has increased N-oxide emissions 16-fold, with its effects most pronounced in summer and at the N-rich centers of dense, monospecific stands.     

Soil warming alters microbial substrate use in alpine soils

Will warming lead to an increased use of older soil organic carbon (SOC) by microbial communities, thereby inducing C losses from C‐rich alpine soils? We studied soil microbial community composition, activity, and substrate use after 3 and 4 years of soil warming (+4 °C, 2007–2010) at the alpine treeline in Switzerland. The warming experiment was nested in a free air CO₂ enrichment experiment using depleted ¹³CO₂ (δ¹³C = ?30‰, 2001–2009). We traced this depleted ¹³C label in phospholipid fatty acids (PLFA) of the organic layer (0–5 cm soil depth) and in C mineralized from root‐free soils to distinguish substrate ages used by soil microorganisms: fixed before 2001 (‘old’), from 2001 to 2009 (‘new’) or in 2010 (‘recent’). Warming induced a sustained stimulation of soil respiration (+38%) without decline in mineralizable SOC. PLFA concentrations did not reveal changes in microbial community composition due to soil warming, but soil microbial metabolic activity was stimulated (+66%). Warming decreased the amount of new and recent C in the fungal biomarker 18:2ω6,9 and the amount of new C mineralized from root‐free soils, implying a shift in microbial substrate use toward a greater use of old SOC. This shift in substrate use could indicate an imbalance between C inputs and outputs, which could eventually decrease SOC storage in this alpine ecosystem.     

Reproductive morphology of Sargentodoxa cuneata (Lardizabalaceae) and its systematic implications

The reproductive morphology of Sargentodoxa cuneata (Oliv) Rehd. et Wils. is investigated through field, herbarium, and laboratory observations. Sargentodoxa may be either dioecious or monoecious. The functionally unisexual flowers are morphologically bisexual, at least developmentally. The anther is tetrasporangiate, and its wall, of which the development follows the basic type, is composed of an epidermis, endothecium, two middle layers, and a tapetum. The tapetum is of the glandular type. Microspore cytokinesis is simultaneous, and the microspore tetrads are tetrahedral. Pollen grains are two-celled when shed. The mature ovule is crassinucellate and bitegmic, and the micropyle is formed only by the inner integument. Megasporocytes undergo meiosis resulting in the formation of four megaspores in a linear tetrad. The functional megaspore develops into an eight-nucleate embryo sac after three rounds of mitosis. The mature embryo sac consists of an egg apparatus (an egg and two synergids), a central cell, and three antipodal cells. The pattern of the embryo sac development follows a monosporic Polygonum type. Comparisons with allied groups show that Sargentodoxa shares more synapomorphies with the Lardizabalaceae than other Ranunculales. Characteristics of its reproductive morphology are consistent with the placement of Sargentodoxa as the sister group of the remaining Lardizabalaceae. It does not possess a sufficient number of apomorphic characters to justify its separation into a separate family or subfamily. It is best retained as a member of the Lardizabalaceae.