A novel role of sulfate in promoting Mn phytoextraction efficiency and alleviating Mn stress in Polygonum lapathifolium Linn.

A hydroponic method was performed to explore the effects of sulfate supply on the growth, manganese (Mn) accumulation efficiency and Mn stress alleviation mechanisms of Polygonum lapathifolium Linn. Three Mn concentrations (1, 8 and 16 mmol L-1, representing low (Mn1), medium (Mn8) and high (Mn16) concentrations, respectively) were used. Three sulfate (S) levels (0, 200, and 400 µmol L-1, abbreviated as S0, S200 and S400, respectively) were applied for each Mn concentration. (1) The average biomass (g plant-1) of P. lapathifolium was ordered as Mn8 (6.36) > Mn1 (5.25) > Mn16 (4.16). Under Mn16 treatment, S addition increased (P < 0.05) biomass by 29.96% (S200) and 53.07% (S400) compared to that S0. The changes in the net photosynthetic rate and mean daily increase in biomass were generally consistent with the changes in biomass. (2) Mn accumulation efficiency (g plant-1) was ordered as Mn8 (99.66) > Mn16 (58.33) > Mn1 (27.38); and S addition increased (p < 0.05) plant Mn accumulation and Mn transport, especially under Mn16 treatment. (3) In general, antioxidant enzyme activities (AEAs) and malondialdehyde (MDA) in plant leaves were ordered in Mn16 > Mn8 > Mn1. Sulfate addition decreased (P < 0.05) AEAs and MDA under Mn16 treatment, while the changes were minor under Mn1 and Mn8 treatments. (4) Amino acid concentrations generally increased with increasing Mn concentration and S level. In summary, the medium Mn treatment promoted plant growth and Mn bioaccumulation; sulfate, especially at 400 µmol L-1 S, can effectively promote plant growth and Mn accumulation efficiency. The most suitable bioremediation strategy was Mn16 with 400 µmol L-1 S.

Production of Antioxidant Molecules in Polygonum aviculare (L.) and Senecio vulgaris (L.) under Metal Stress: A Possible Tool in the Evaluation of Plant Metal Tolerance.

Plants growing on heavy metal (HM)-polluted soils show toxicity symptoms, such as chlorosis and growth reduction, and undergo oxidative stress due to the formation of reactive oxygen species (ROS). Plants overcome oxidative stress by producing a wide range of antioxidant molecules, such as polyphenols and flavonoids. The aim of the present work was to study the accumulation of these molecules in response to increasing concentrations of Cd, Cr, Cu, Ni, Pb and Zn and to assess whether they can be used as a tool in assessing metal-related stress in Polygonum aviculare and Senecio vulgaris. On average, P. aviculare shoots accumulated lower amounts of metals than S. vulgaris shoots. The uptake of all six elements was correlated and proportional to their concentration in the nutrient solution (ρ > 0.9), with the bioaccumulation factor (BAF) being >1 for most of them. The present research demonstrated that 82% of the samples showed a good correlation (|ρ| > 0.5) between the level of polyphenols, flavonoids and antioxidant activity and the metal concentration in plant shoots, confirming that the metal stress level and production of phenolic compounds having antioxidant activity were strictly connected. Nonetheless, the mere quantification of these molecules cannot identify the type of metal that caused the oxidative stress, neither determine the concentration of the stressors. The five tested populations of each species did not show any specific adaptation to the environment of origin.

Transgenerational effects of parental light environment on progeny competitive performance and lifetime fitness.

Plant and animal parents may respond to environmental conditions such as resource stress by altering traits of their offspring via heritable non-genetic effects. While such transgenerational plasticity can result in progeny phenotypes that are functionally pre-adapted to the inducing environment, it is unclear whether such parental effects measurably enhance the adult competitive success and lifetime reproductive output of progeny, and whether they may also adversely affect fitness if offspring encounter contrasting conditions. In glasshouse experiments with inbred genotypes of the annual plant Polygonum persicaria, we tested the effects of parental shade versus sun on (a) competitive performance of progeny in shade, and (b) lifetime reproductive fitness of progeny in three contrasting treatments. Shaded parents produced offspring with increased fitness in shade despite competition, as well as greater competitive impact on plant neighbours. Inherited effects of parental light conditions also significantly altered lifetime fitness: parental shade increased reproductive output for progeny in neighbour and understorey shade, but decreased fitness for progeny in sunny, dry conditions. Along with these substantial adaptive and maladaptive transgenerational effects, results show complex interactions between genotypes, parent environment and progeny conditions that underscore the role of environmental variability and change in shaping future adaptive potential. This article is part of the theme issue 'The role of plasticity in phenotypic adaptation to rapid environmental change'.

Weed Growth Stage Estimator Using Deep Convolutional Neural Networks.

This study outlines a new method of automatically estimating weed species and growth stages (from cotyledon until eight leaves are visible) of in situ images covering 18 weed species or families. Images of weeds growing within a variety of crops were gathered across variable environmental conditions with regards to soil types, resolution and light settings. Then, 9649 of these images were used for training the computer, which automatically divided the weeds into nine growth classes. The performance of this proposed convolutional neural network approach was evaluated on a further set of 2516 images, which also varied in term of crop, soil type, image resolution and light conditions. The overall performance of this approach achieved a maximum accuracy of 78% for identifying Polygonum spp. and a minimum accuracy of 46% for blackgrass. In addition, it achieved an average 70% accuracy rate in estimating the number of leaves and 96% accuracy when accepting a deviation of two leaves. These results show that this new method of using deep convolutional neural networks has a relatively high ability to estimate early growth stages across a wide variety of weed species.

Physiological response of Polygonum perfoliatum L. following exposure to elevated manganese concentrations.

Polygonum perfoliatum L. is a Mn-tolerant plant as considered having the potential to revegetate in manganese mine wasteland. The glasshouse experiments were carried out to evaluate its tolerance and physiological response in different Mn concentrations (5, 500, 1000, 2000, 5000, and 10,000 µmol L-1). Absorption bands of P. perfoliatum differed greatly in lipids, proteins, and carbohydrates. With elevated levels of Mn (5-2000 µmol L-1), absorbance changed little, which demonstrated that lower Mn concentrations had negligible influence on transport functions. As Mn concentrations in excess of 2000 µmol L-1, absorbance increased slightly but eventually decreased. Furthermore, a hydroponic culture was carried out in order to study its changes of ultrastructure with the increasing Mn concentrations (5, 1000, and 10,000 µmol L-1). Lower Mn levels with 5 and 1000 µmol L-1 had no breakage function to the ultrastructure of P. perfoliatum. However, as Mn concentration was up to 10,000 µmol L-1, visible damages began to appear, the quantity of mitochondria in root cells increased, and the granum lamellae of leaf cell chloroplasts presented a disordered state. In comparison with the controls, black agglomerations were found in the cells of P. perfoliatum under the controlling concentration of Mn with 1000 and 10,000 µmol L-1 for 30 days, which became obvious at higher Mn concentrations. As Mn concentration was 10,000 µmol L-1, a kind of new acicular substance was developed in leaf cells and intercellular spaces, possibly indicating a resistance mechanism in P. perfoliatum. These results confirm that P. perfoliatum shows potential for the revegetation of abandoned manganese tailings.

Evolutionary potential for increased invasiveness: High-Performance Polygonum cespitosum genotypes are competitively superior in full sun.

PREMISE OF STUDY: The presence of genetic variation for traits that contribute to ecological range expansion can provide the potential for introduced taxa to evolve greater invasiveness. Genotypes that contribute to the spread of introduced range populations must have the ability to maintain fitness under changing environmental stress and competitive intensity. Previously, we identified a subset of genotypes in populations of the invasive annual Polygonum cespitosum that express consistently high reproductive fitness in diverse (shaded, dry, and resource-rich) conditions. Here, we investigated whether these broadly adaptive (High-Performance) genotypes also show a competitive advantage over conspecifics in full sun and/or shade. METHODS: We grew a population-balanced sample of 13 High-Performance and 13 'Control' genotypes in intraspecific competitive arrays, comprising all four possible combinations of High-Performance vs. Control target plants and competitive backgrounds, in both full sun and shaded glasshouse environments. KEY RESULTS: In full sun, High-Performance genotypes (1) better maintained growth and reproductive output despite competition and (2) more strongly suppressed growth and reproduction of target plants. However, genotypes did not differ significantly in shade. CONCLUSIONS: Competitive superiority in open conditions may contribute to increasing predominance of these broadly adapted genotypes in introduced-range Polygonum cespitosum populations, and hence to the evolution of greater invasiveness. This study provides insight into the role of genotypic variation for ecological traits in the range expansion of a contemporary plant invader. It also highlights how such variation can be differently expressed in alternative environments (gene by environment interaction).

P accumulation and physiological responses to different high P regimes in Polygonum hydropiper for understanding a P-phytoremediation strategy.

Phosphorus (P) accumulators used for phytoremediation vary in their potential to acquire P from different high P regimes. Growth and P accumulation in Polygonum hydropiper were both dependent on an increasing level of IHP (1-8 mM P) and on a prolonged growth period (3-9 weeks), and those of the mining ecotype (ME) were higher than the non-mining ecotype (NME). Biomass increments in root, stem, and leaf of both ecotypes were significantly greater in IHP relative to other organic P (Po) sources (G1P, AMP, ATP), but lower than those in inorganic P (Pi) treatment (KH2PO4). P accumulation in the ME exceeded the NME from different P regimes. The ME demonstrated higher root activity compared to the NME grown in various P sources. Acid phosphatase (Apase) and phytase activities in root extracts of both ecotypes grown in IHP were comparable to that in Pi, or even higher in IHP. Higher secreted Apase and phytase activities were detected in the ME treated with different P sources relative to the NME. Therefore, the ME demonstrates higher P-uptake efficiency and it is a potential material for phytoextraction from P contaminated areas, irrespective of Pi or Po contamination.

Sexual reproduction of Japanese knotweed (Fallopia japonica s.l.) at its northern distribution limit: new evidence of the effect of climate warming on an invasive species.

PREMISE OF THE STUDY: In response to climate warming, plant species may shift their distribution northward, but such a process is slow and hard to detect. Alternatively, phenological changes (earlier flowering) are expected as first adaptations for populations located near their distribution limit. That could be the case for the invasive Japanese knotweed (Fallopia japonica s.l., including the hybrid Bohemian knotweed F. ×bohemica). We hypothesized that climate warming now allows the species to produce viable seeds in the northernmost populations. METHODS: Seeds were collected along a 550 km long transect in Quebec, Canada, and tested for germination. The genetic diversity of a population was determined using polymorphic microsatellite markers to verify whether the species is actually producing new individuals through sexual reproduction. KEY RESULTS: Japanese knotweed produces, in Quebec, a large number of seeds with a high germination rate (up to 93%). The geographical limit for viable seed production in North America has been extended to Quebec City, about 500 km north of the formerly reported limit. Bohemian knotweeds are genetically diverse, while true Japanese knotweeds all share a common multilocus genotype. This suggests that Bohemian knotweed stands mostly arose from seed, while true Japanese knotweeds result only from the propagation of rhizome or stem fragments. CONCLUSIONS: The effect of climate change is already palpable on the phenology of invasive plant species at their northern distribution limit. Bohemian knotweed, which until recently was rare in Quebec, could rapidly spread in the near future with the help of an additional diaspore type (seeds).

[Phenological characteristics of introduced Polygonum viviparum from high altitude to low altitude area].

OBJECTIVE: To explore the phenological characteristics of Polygonum viviparum introduced from high altitude to low altitude area. METHODS: To introduce the root and seed of Polygonum viviparum from high altitude to low altitude area and collect their growth and phenological data. RESULTS: In low altitude area, Polygonum viviparum germinated at the beginning of March, grew from March to the end of July, withered during the whole August due to high temperature, recovered from the end of August to the beginning of October, and then withered again due to low temperature. Its reproduction lasted from April to the end of July, stagnated from the beginning of August to the middle of September, and recovered from the middle of September to the end of October. CONCLUSION: The high temperature of August in low altitude area is the bottleneck season for Polygonum viviparum, yet it can grow normally while such technologies are applied to its culture as early seeding, culture seedling with fertilizing soil ball, complete overshadow etc.

High-performance genotypes in an introduced plant: insights to future invasiveness.

Maintaining high reproductive output in diverse conditions has consistently been found to promote invasiveness in introduced taxa. Following on this key observation, studies have compared the performance across environments of invasive vs. native congeners, and of introduced vs. native populations within invasive species. Performance differences among genotypes within introduced species have received far less attention, although such genetic variation could be critical to invasive potential. If an introduced species contains genotypes that can maintain high fitness across contrasting environments, such broadly adaptive, high-performance genotypes could promote and shape the species' immediate spread across multiple habitats. Furthermore, their presence could lead to the evolution of greater aggressiveness in the species, as these high performers increase in frequency. We investigated the existence and distribution of high-performance genotypes in Polygonum cespitosum, a newly invasive Asian annual. We raised 416 genotypes, collected from 14 North American populations, under resource-rich conditions to identify potential high-performance genotypes (the top 5% in total reproductive output). We then compared their fitness, life history, and functional traits to a random group of the remaining genotypes in three contrasting environments to ask the following: (1) Do consistently high-performance genotypes (i.e., genotypes with high relative fitness in diverse conditions) exist within introduced-range populations? (2) If so, do these high-performance genotypes possess distinctive life history and/or functional traits? (3) Do these genotypes occur in all populations or in only a subset of populations? Genotypes initially identified as high-performance in favorable conditions also had higher reproductive output in resource-limited environments. Their fitness advantage compared with control genotypes varied in magnitude from one environment to another but was significant within all three test environments. High-performance genotypes shared a developmental syndrome characterized by rapid and high germination, fast seedling growth, early reproductive onset, and high reproductive allocation, but they did not differ in other functional traits. P. cespitosum includes a subset of genotypes with accelerated development and significantly greater fitness in both favorable and stressful conditions. The nonrandom distribution of these high-performance genotypes among populations in the species' introduced range highlights the importance of genotypic and population-level variation for invasion dynamics.

[Habitat survey and biological characteristics study of Polygonum multiflorum germplasms in Guizhou region].

OBJECTIVE: To provide reference in selecting premium provenance and improve the cultivation techniques of Polygonum multiflorum. METHODS: Field survey, routine field-observation and sampling fixed plant for analysis in lab were adopted. RESULTS: The growing adaptability of Polygonum multiflorum was very strong, which growed flourishly in the condition with adequate light, ample rainfall, rich heat and fertile soil; Along with the lower of latitude, the vegetative period was prolonged and reproductive stage was delayed, which prolonged the time of roots' nutrition acquisition. Time for root shoot ratio increasing continuously of low latitude germplasms was higher than that of higher latitude germplasms. CONCLUSION: Polygonum multiflorum germplasms have different biological characteristics because of different regions and habitats, which can provide useful reference for selecting premium provenance and adjusting measures to local conditions in different areas.

Phenotypic plasticity and population differentiation in an ongoing species invasion.

The ability to succeed in diverse conditions is a key factor allowing introduced species to successfully invade and spread across new areas. Two non-exclusive factors have been suggested to promote this ability: adaptive phenotypic plasticity of individuals, and the evolution of locally adapted populations in the new range. We investigated these individual and population-level factors in Polygonum cespitosum, an Asian annual that has recently become invasive in northeastern North America. We characterized individual fitness, life-history, and functional plasticity in response to two contrasting glasshouse habitat treatments (full sun/dry soil and understory shade/moist soil) in 165 genotypes sampled from nine geographically separate populations representing the range of light and soil moisture conditions the species inhabits in this region. Polygonum cespitosum genotypes from these introduced-range populations expressed broadly similar plasticity patterns. In response to full sun, dry conditions, genotypes from all populations increased photosynthetic rate, water use efficiency, and allocation to root tissues, dramatically increasing reproductive fitness compared to phenotypes expressed in simulated understory shade. Although there were subtle among-population differences in mean trait values as well as in the slope of plastic responses, these population differences did not reflect local adaptation to environmental conditions measured at the population sites of origin. Instead, certain populations expressed higher fitness in both glasshouse habitat treatments. We also compared the introduced-range populations to a single population from the native Asian range, and found that the native population had delayed phenology, limited functional plasticity, and lower fitness in both experimental environments compared with the introduced-range populations. Our results indicate that the future spread of P. cespitosum in its introduced range will likely be fueled by populations consisting of individuals able to express high fitness across diverse light and moisture conditions, rather than by the evolution of locally specialized populations.

Invasive knotweeds are highly tolerant to salt stress.

Japanese knotweed s.l. are some of the most invasive plants in the world. Some genotypes are known to be tolerant to the saline concentrations found in salt marshes. Here we focus on tolerance to higher concentrations in order to assess whether the species are able to colonize and establish in highly stressful environments, or whether salt is an efficient management tool. In a first experiment, adult plants of Fallopia japonica, Fallopia × bohemica and Fallopia sachalinensis were grown under salt stress conditions by watering with saline concentrations of 6, 30, 120, or 300 g L(-1) for three weeks to assess the response of the plants to a spill of salt. At the two highest concentrations, their leaves withered and fell. There were no effects on the aboveground parts at the lowest concentrations. Belowground dry weight and number of buds were reduced from 30 and 120 g L(-1) of salt, respectively. In a second experiment, a single spraying of 120 g L(-1) of salt was applied to individuals of F. × bohemica and their stems were clipped to assess the response to a potential control method. 60 % of the plants regenerated. Regeneration was delayed by the salt treatment and shoot growth slowed down. This study establishes the tolerance of three Fallopia taxa to strong salt stress, with no obvious differences between taxa. Their salt tolerance could be an advantage in their ability to colonize polluted environments and to survive to spills of salt.

Adaptive transgenerational plasticity in an annual plant: grandparental and parental drought stress enhance performance of seedlings in dry soil.

Stressful parental (usually maternal) environments can dramatically influence expression of traits in offspring, in some cases resulting in phenotypes that are adaptive to the inducing stress. The ecological and evolutionary impact of such transgenerational plasticity depends on both its persistence across generations and its adaptive value. Few studies have examined both aspects of transgenerational plasticity within a given system. Here we report the results of a growth-chamber study of adaptive transgenerational plasticity across two generations, using the widespread annual plant Polygonum persicaria as a naturally evolved model system. We grew five inbred Polygonum genetic lines in controlled dry vs. moist soil environments for two generations in a fully factorial design, producing replicate individuals of each genetic line with all permutations of grandparental and parental environment. We then measured the effects of these two-generational stress histories on traits critical for functioning in dry soil, in a third (grandchild) generation of seedling offspring raised in the dry treatment. Both grandparental and parental moisture environment significantly influenced seedling development: seedlings of drought-stressed grandparents or parents produced longer root systems that extended deeper and faster into dry soil compared with seedlings of the same genetic lines whose grandparents and/or parents had been amply watered. Offspring of stressed individuals also grew to a greater biomass than offspring of nonstressed parents and grandparents. Importantly, the effects of drought were cumulative over the course of two generations: when both grandparents and parents were drought-stressed, offspring had the greatest provisioning, germinated earliest, and developed into the largest seedlings with the most extensive root systems. Along with these functionally appropriate developmental effects, seedlings produced after two previous drought-stressed generations had significantly greater survivorship in very dry soil than did seedlings with no history of drought. These findings show that plastic responses to naturalistic resource stresses experienced by grandparents and parents can "preadapt" offspring for functioning under the same stresses in ways that measurably influence realized fitness. Possible implications of these environmentally-induced, inherited adaptations are discussed with respect to ecological distribution, persistence under novel stresses, and evolution in natural populations.

[Ecology suitability of Polygonum capitatum in Guizhou province based on topographical conditions].

OBJECTIVE: To study ecology suitability rank dividing of Polygonum capitatum for selecting artificial planting base and high-quality industrial raw material in Guizhou province. METHOD: Based on the investigation of PCB and DEM data of Guizhou province, the relationship between the gallic acid content in P. capitatum and topographical conditions was analyzed by statistical analysis. The geographic information systems (GIS)-based assessment and landscape ecological principles were applied to assess ecology suitability areas of P. capitatum in Guizhou. RESULT AND CONCLUSION: slope, aspect and altitude are main topographical factors that affect the content of gallic acid in P. capitatum. The gallic acid content of P. capitatum is higher in the lower altitude, shady slope and smaller slope areas. The gallic acid content is higher in the eastern areas of Guizhou province.

Altitudinal variations in flower and bulbil production of an alpine perennial, Polygonum viviparum L. (Polygonaceae).

Two opposite views exist regarding sexual versus asexual reproductive performance of Polygonum viviparum. One suggests that increasing altitude favors flower production, while the other suggests that increasing altitude increases bulbil production. In this study, we present an investigation of the reproductive performance of 13 populations of P. viviparum on the Qinghai-Tibet Plateau (QTP). Our results show that, with increasing altitude, the height of inflorescence and total number of flowers and bulbils decrease significantly, but there is no significant effect on bulbil and flower number. In addition, there is a weak correlation between the proportion of flowers per population and altitude in our study sites due to the exception population 12, which is in a disturbed habitat. We conclude that more resources might be allocated to flowers in populations at higher altitudes, indicating the importance of sexual reproduction over asexual reproduction in alpine plants of QTP.

[Effects of compensation capacity and palatability on the dominance of plant species in grazing community].

With simulated mowing experiment and field survey, the compensation capacity and dominance shift of nine alpine plant species in grazing community were studied. The results showed that for most test species, there existed definite correlations between their compensation capacity and palatability. The species with better palatability, i.e., Astragalus polycladus, Medicago rythenica, Kobresia humilis, and Polygonum viviparvum, had higher compensation capacity, with their compensation index being 1.013, 0.907, 0.849, and 0.802, respectively, followed by Elymus nutans, with its compensation index being 0.668, while the species with poorer palatability, i.e., Taraxacum tibetanum, Swertis bimaculata, and Ajania tenuifolia had lower compensation capacity, with their compensation index being 0.649, 0.587, and 0.553, respectively. Festuca sinensis was more palatable but had the lowest compensation index (0.473). The nine species had three types of dominance shift, i.e., decreasing, increasing, and neutral. F. sinensis was of decreasing type, E. nutans, A. polycladus and P. viviparvum were of neutral, and the other five species were of increasing type. The compensation capacity and palatability of plant species in grazing community could explain their dominance shift to a certain extent.

Response of Polygonum viviparum species and community level to long-term livestock grazing in alpine shrub meadow in Qinghai-Tibet Plateau.

Grazing by domestic herbivores is generally recognized as a major ecological factor and an important evolutionary force in grasslands. Grazing has both extensive and profound effects on individual plants and communities. We investigated the response patterns of Polygonum viviparum species and the species diversity of an alpine shrub meadow in response to long-term livestock grazing by a field manipulative experiment controlling livestock numbers on the Qinghai-Tibet Plateau in China. Here, we hypothesize that within a range of grazing pressure, grazing can alter relative allocation to different plant parts without changing total biomass for some plant species if there is life history trade-offs between plant traits. The same type of communities exposed to different grazing pressures may only alter relative species' abundances or species composition and not vary species diversity because plant species differ in resistant capability to herbivory. The results show that plant height and biomass of different organs differed among grazing treatments but total biomass remained constant. Biomass allocation and absolute investments to both reproduction and growth decreased and to belowground storage increased with increased grazing pressure, indicating the increasing in storage function was attained at a cost of reducing reproduction of bulbils and represented an optimal allocation and an adaptive response of the species to long-term aboveground damage. Moreover, our results showed multiform response types for either species groups or single species along the gradient of grazing intensity. Heavy grazing caused a 13.2% increase in species richness. There was difference in species composition of about 18%-20% among grazing treatment. Shannon-Wiener (H') diversity index and species evenness (E) index did not differ among grazing treatments. These results support our hypothesis.

Transient population dynamics in periodic matrix models: methodology and effects of cyclic permutations.

Many biological populations are subject to periodically changing environments such as years with or without fire, or rotation of crop types. The dynamics and management options for such populations are frequently investigated using periodic matrix models. However the analysis is usually limited to long-term results (asymptotic population growth rate and its sensitivity to perturbations of vital rates). In non-periodic matrix models it has been shown that long-term results may be misleading as populations are rarely in their stable structure. We therefore develop methods to analyze transient dynamics of periodic matrix models. In particular, we show how to calculate the effects of perturbations on population size within and at the end of environmental cycles. Using a model of a weed population subject to a crop rotation, we show that different cyclic permutations produce different patterns of sensitivity of population size and different population sizes. By examining how the starting environment interacts with the initial conditions, we explain how different patterns arise. Such understanding is critical to developing effective management and monitoring strategies for populations subject to periodically recurring environments.