Comparative Analysis of Environment-Responsive Alternative Splicing in the Inflorescences of Cultivated and Wild Tomato Species.

Cultivated tomato (Solanum lycopersicum) is bred for fruit production in optimized environments, in contrast to harsh environments where their ancestral relatives thrive. The process of domestication and breeding has profound impacts on the phenotypic plasticity of plant development and the stress response. Notably, the alternative splicing (AS) of precursor message RNA (pre-mRNA), which is one of the major factors contributing to transcriptome complexity, is responsive to developmental cues and environmental change. To determine a possible association between AS events and phenotypic plasticity, we investigated environment-responsive AS events in the inflorescences of cultivated tomato and its ancestral relatives S. pimpinellifolium. Despite that similar AS frequencies were detected in the cultivated tomato variety Moneymaker and two S. pimpinellifolium accessions under the same growth conditions, 528 genes including splicing factors showed differential splicing in the inflorescences of plants grown in open fields and plastic greenhouses in the Moneymaker variety. In contrast, the two S. pimpinellifolium accessions, LA1589 and LA1781, had 298 and 268 genes showing differential splicing, respectively. Moreover, seven heat responsive genes showed opposite expression patterns in response to changing growth conditions between Moneymaker and its ancestral relatives. Accordingly, there were eight differentially expressed splice variants from genes involved in heat response in Moneymaker. Our results reveal distinctive features of AS events in the inflorescences between cultivated tomato and its ancestral relatives, and show that AS regulation in response to environmental changes is genotype dependent.

Selection against early flowering in geothermally heated soils is associated with pollen but not prey availability in a carnivorous plant.

PREMISE: In high-latitude environments, plastic responses of phenology to increasing spring temperatures allow plants to extend growing seasons while avoiding late frosts. However, evolved plasticity might become maladaptive if climatic conditions change and spring temperatures no longer provide reliable cues for conditions important for fitness. Maladaptative phenological responses might be related to both abiotic factors and mismatches with interacting species. When mismatches arise, we expect selection to favor changes in phenology. METHODS: We combined observations along a soil temperature gradient in a geothermally heated area with pollen and prey supplementation experiments and examined how phenotypic selection on flowering time in the carnivorous plant Pinguicula vulgaris depends on soil temperature, and pollen and prey availability. RESULTS: Flowering advanced and fitness decreased with increasing soil temperature. However, in pollen-supplemented plants, fitness instead increased with soil temperature. In heated soils, there was selection favoring later flowering, while earlier flowering was favored in unheated soils. This pattern remained also after artificially increasing pollen and prey availability. CONCLUSIONS: Plant-pollinator mismatches can be an important reason why evolved plastic responses of flowering time to increasing spring temperatures become maladaptive under novel environmental conditions, and why there is selection to delay flowering. In our study, selection for later flowering remained after artificially increasing pollen availability, suggesting that abiotic factors also contribute to the observed selection. Identifying the factors that make evolved phenological responses maladaptive under novel conditions is fundamental for understanding and predicting evolutionary responses to climate warming.

Phenotypic and transcriptomic responses of the shade-grown species Panax ginseng to variable light conditions.

BACKGROUND AND AIMS: Elucidating how plant species respond to variable light conditions is important to understand the ecological adaptation to heterogeneous natural habitats. Plant performance and its underlying gene regulatory network have been well documented in sun-grown plants. However, the phenotypic and molecular responses of shade-grown plants under variable light conditions have remained largely unclear. METHODS: We assessed the differences in phenotypic performance between Panax ginseng (shade-grown) and Arabidopsis thaliana (sun-grown) under sunlight, shade and deep-shade conditions. To further address the molecular bases underpinning the phenotypic responses, we compared time-course transcriptomic expression profiling and candidate gene structures between the two species. KEY RESULTS: Our results show that, compared with arabidopsis, ginseng plants not only possess a lower degree of phenotypic plasticity among the three light conditions, but also exhibit higher photosynthetic efficiency under shade and deep-shade conditions. Further comparisons of the gene expression and structure reveal that differential transcriptional regulation together with increased copy number of photosynthesis-related genes (e.g. electron transfer and carbon fixation) may improve the photosynthetic efficiency of ginseng plants under the two shade conditions. In contrast, the inactivation of phytochrome-interacting factors (i.e. absent and no upregulation of the PIF genes) are potentially associated with the observed low degree of phenotypic plasticity of ginseng plants under variable light conditions. CONCLUSIONS: Our study provides new insights into how shade-grown plants respond to variable light conditions. Candidate genes related to shade adaptation in ginseng provide valuable genetic resources for future molecular breeding of high-density planting crops.

TNFα activation and TGFß blockage act synergistically for smooth muscle cell calcification in patients with venous thrombosis via TGFß/ERK pathway.

Venous calcification has been observed in post-thrombotic syndrome (PTS) patients; yet, the cell types and possible mechanisms regulating this process are still unclear. We evaluated the calcium deposition within the venous wall, the cell type involved in the calcified remodelling of the venous wall after thrombosis and explored possible mechanisms in vitro. Calcium deposition was found in human specimens of superficial thrombotic veins and was co-localized with VSMCs markers αSMA and TAGLN (also known as SM22α). Besides, the expression of osteogenesis-related genes was dramatically changed in superficial thrombotic veins. Moreover, the inhibition of the TGFß signalling pathway after TNFα treatment effectively induced the expression of osteogenic phenotype markers, the calcium salt deposits and the obvious phosphorylation of ERK1/2 and JNK2 in the VSMCs calcification model. Supplementing TGFß2 or blocking the activation of the ERK/MAPK signalling pathway prevented the transformation of VSMCs into osteoblast-like cells in vitro. Taken together, VSMCs have an important role in venous calcification after thrombosis. Supplementing TGFß2 or inhibiting the ERK/MAPK signalling pathway can reduce the appearance of VSMCs osteogenic phenotype. Our findings may present a novel therapeutic approach to prevent of vascular calcification after venous thrombosis.

Plasticity in floral longevity and sex-phase duration of Lobelia siphilitica in response to simulated pollinator declines.

PREMISE: Pollinator declines can reduce the quantity and quality of pollination services, resulting in less pollen deposited on flowers and lower seed production by plants. In response to these reductions, plant species that cannot autonomously self-pollinate and thus are dependent on pollinators to set seed could plastically adjust their floral traits. Such plasticity could increase the opportunity for outcross pollination directly, as well as indirectly by affecting inflorescence traits. METHODS: To test whether plants can respond to pollinator declines by plastically adjusting their floral traits, we simulated declines by experimentally reducing pollinator access to Lobelia siphilitica plants and measuring two traits of early- and late-season flowers: (1) floral longevity; and (2) sex-phase duration. To test whether plasticity in these floral traits affected inflorescence traits, we measured daily display size and phenotypic gender. RESULTS: We found that experimentally reducing pollination did not affect female-phase duration, but did extend the male-phase duration of early-season flowers by 13% and the longevity of late-season flowers by 12.8%. However, plants with an extended male phase did not have a more male-biased phenotypic gender, and plants with an extended floral longevity did not have a larger daily display. CONCLUSIONS: Our results suggest that plants can respond to pollinator declines by plastically adjusting both the longevity and sex-phase duration of their flowers. If this plasticity increases the opportunity for outcross pollination, then it could be one mechanism by which pollinator-dependent plant species maintain seed production as pollinators decline.

Maternal consumption of É·3 attenuates metabolic disruption elicited by saturated fatty acids-enriched diet in offspring rats.

BACKGROUND AND AIMS: High-fat diet (HFD) intake during gestation and lactation has been associated with an increased risk of developing cardiometabolic disorders in adult offspring. We investigated whether metabolic alterations resulting from the maternal consumption of HFD are prevented by the addition of omega-3 (É·3) in the diet. METHODS AND RESULTS: Wistar rat dams were fed a control (C: 19% of lipids and É·6:É·3 = 12), HF (HF: 33% lipids and É·6:É·3 = 21), or HF enriched with É·3 (HFω3: 33% lipids and É·6:É·3 = 9) diet during gestation and lactation, and their offspring food consumption, murinometric measurements, serum levels of metabolic markers, insulin and pyruvate sensitivity tests were evaluated. The maternal HFD increased body weight at birth, dyslipidemia, and elevated fasting glucose levels in the HF group. The enrichment of É·3 in the maternal HFD led to lower birth weight and improved lipid, glycemic, and transaminase biochemical profile of the HFω3 group until the beginning of adulthood. However, at later adulthood of the offspring, there was no improvement in these biochemical parameters. CONCLUSION: Our findings show the maternal consumption of high-fat É·3-rich diet is able to attenuate or prevent metabolic disruption elicited by HFD in offspring until 90 days old, but not in the long term, as observed at 300 days old of the offspring.

Insights into in vitro phenotypic plasticity, growth and secondary metabolites of the mycobiont isolated from the lichen Platygramme caesiopruinosa.

The choice of inoculum for successful isolation and establishment of axenic lichen mycobiont culture is a key step towards eliminating endolichenic and lichenicolous fungi and other microbial contamination. The nutritional requirements of each lichen species are unique. This work reports on the isolation, phenotypic plasticity, growth and secondary metabolites from mycobiont culture of the pantropical lichen Platygramme caesiopruinosa. Media composition [Malt yeast extract (MY), Modified Murashige and Skoog (MMS) and Lilly and Barnett (LB) media] was optimized to determine nutritional requirements for optimal growth of this species as assessed by dry biomass and the occurrence of secondary metabolite. Furthermore, the role of different carbon sources in affecting growth, growth stages, phenotypic plasticity, biomass and spectrum of secondary metabolites produced of this mycobiont was examined. The molecular identity of the mycobiont culture was confirmed by amplifying mitochondrial small subunit (mtSSU) sequences. Cultures showed optimum biomass production in MY medium with 10% sucrose. The secondary metabolite profiles for each culture treatment were characterized using High-performance Thin-Layer Chromatography (HPTLC) and Gas Chromatography with Mass Spectrometric (GC-MS) analysis. The HPTLC spectral comparison, phenolic and iodine confirmatory analysis revealed the absence of phenolic metabolites and the presence of non-phenolic metabolites in mycobiont extracts, while GC-MS analysis revealed the biosynthesis of side chain fatty acids, hydrocarbons and sugar alcohol in mycobiont cultures treated with 10% supplemented sucrose as a carbon source.

The seeds of invasion: enhanced germination in invasive European populations of black locust (Robinia pseudoacacia L.) compared to native American populations.

Local adaptation and the evolution of phenotypic plasticity may facilitate biological invasions. Both processes can enhance germination and seedling recruitment, which are crucial life-history traits for plants. The rate, timing and speed of germination have recently been documented as playing a major role during the invasion process. Black locust (Robinia pseudoacacia L.) is a North American tree, which has spread widely throughout Europe. A recent study demonstrated that a few populations are the source of European black locust. Thus, invasive populations can be compared to native ones in order to identify genetic-based phenotypic differentiation and the role of phenotypic plasticity can thereby be assessed. A quantitative genetics experiment was performed to evaluate 13 juvenile traits of both native and invasive black locust populations (3000 seeds, 20 populations) subjected to three different thermal treatments (18 °C, 22 °C and 31 °C). The results revealed European populations to have a higher germination rate than the native American populations (88% versus 60%), and even when genetic distance between populations was considered. Moreover, this trait showed lower plasticity to temperature in the invasive range than in the native one. Conversely, other studied traits showed high plasticity to temperature, but they responded in a similar way to temperature increase: the warmer the temperature, the higher the growth rate or germination traits values. The demonstrated genetic differentiation between native and invasive populations testifies to a shift between ranges for the maximum germination percentage. This pattern could be due to human-mediated introduction of black locust.

Predictive Chromatography of Leaf Extracts Through Encoded Environmental Forcing on Phytochemical Synthesis.

Environment fluctuations can influence a plant's phytochemical profile via phenotypic plasticity. This adaptive response ensures a plant's survival under fluctuating growth conditions. However, the resulting plant extract composition becomes unpredictable, which is a problem for highly standardized medicinal applications. Here we demonstrate, for the first time, the feasibility of tracking the changes in the phytochemical profile based on real-time measurements of a few environment and extract-preparation variables. As a result, we predicted the chromatograms of Blumea balsamifera extracts through an imputation-augmented convolutional neural network, which uses the image-transformed temporal measurements of the variables. We developed a sensor network that collected data in a greenhouse and a training algorithm that concurrently generated a data representation of the implicit plant-environment interactions leading to the mutable chromatograms of leaf extracts. We anticipate the generic applicability of the method for any plant and recognize its potential for addressing the standardization problems in plant therapeutics.

Response to water deficit of semi-desert wild potato Solanum kurtzianum genotypes collected from different altitudes.

Drought-sensitive crops are threatened as a consequence of limited available water due to climate change. The cultivated potato (Solanum tuberosum) is susceptible to drought and within its wild relative species, Solanum kurtzianum is the Argentinian wild potato species best adapted to arid conditions. However, its physiological responses to water deficit (WD) are still missing. Within the distribution of S. kurtzianum, genotypes could be adapted to differential precipitation regimes. The aim of this work was to evaluate responses of three S. kurtzianum genotypes collected at 1100 (G1), 1900 (G2) and 2100 m a.s.l. (G3) to moderate and severe WD. Treatments were imposed since flowering and lasted 36 days. Yield components, morpho-physiological and biochemical responses; and phenotypic plasticity were evaluated. The three genotypes presented mechanisms to tolerate both WD treatments. G1 presented the lowest yield reduction under moderate WD, mainly through a rapid stomatal closure and a modest vegetative growth. The differences among genotypes suggest that local adaptation is taking place within its natural habitat. Also, G2 presented environmentally induced shifts in plasticity for stomatal length and carotenoids, suggesting that phenotypic plasticity has a role in acclimation of plants to WD until selection works.

Chemotaxonomic investigation of Apocynaceae for retronecine-type pyrrolizidine alkaloids using HPLC-MS/MS.

Apocynaceae are well known for diverse specialized metabolites that are distributed in a phylogenetically informative manner. Pyrrolizidine alkaloids (PAs) have been reported sporadically in one lineage in the family, the APSA clade, but few species have been studied to date. We conducted the first systematic survey of Apocynaceae for retronecine-type PAs, sampling leaves from 231 species from 13 of 16 major lineages within the APSA clade using HPLC-MS/MS. We also followed up preliminary evidence for infra-specific variation of PA detectability in Echites umbellatus Jacq. Four precursor ion scans (PREC) were developed for a high-throughput survey for chemicals containing a structural moiety common to many PAs, the retronecine core. We identified with high confidence PAs in 7 of 8 sampled genera of tribe Echiteae, but not in samples from the closely related Odontadenieae and Mesechiteae, confirming the utility of PAs as a taxonomic character in tribal delimitation. Occurrence of PAs in Malouetieae is reported with moderate confidence in Galactophora schomburgkiana Woodson and Eucorymbia alba Stapf, but currently we have low confidence of their presence in Holarrena pubescens Wall. ex G. Don (the one Malouetieae species where they were previously reported), as well as in Holarrena curtisii King & Gamble and in Kibatalia macrophylla (Pierre ex Hua) Woodson. Candidate PAs in some species of Wrightia R. Br. (Wrightieae) and Marsdenia R. Br. (Marsdenieae) are proposed with moderate confidence, but a subset of the compounds in these taxa presenting with a PA-like fragmentation pattern are more likely to be aminobenzoyl glycosides. Candidate PAs are reported in species with predicted (VXXXD) and unexpected (IXXXN) amino acid motifs in their homospermidine synthase-like genes. Detectability of PAs varies among samples of Echites umbellatus and intra-individual plasticity contributes to this variation. Of toxicological importance, novel potential sources of human exposure to pro-toxic PAs were identified in the medicinal plant, Wrightia tinctoria R.Br., and the food plants, Marsdenia glabra Cost. and Echites panduratus A. DC., warranting immediate further research to elucidate the structures of the candidate PAs identified. Method development and limitations are discussed.

Herbicides as anthropogenic drivers of eco-evo feedbacks in plant communities at the agro-ecological interface.

Herbicides act as human-mediated novel selective agents and community disruptors, yet their full effects on eco-evolutionary dynamics in natural communities have only begun to be appreciated. Here, we synthesize how herbicide exposures can result in dramatic phenotypic and compositional shifts within communities at the agro-ecological interface and how these in turn affect species interactions and drive plant (and plant-associates') evolution in ways that can feedback to continue to affect the ecology and ecosystem functions of these assemblages. We advocate a holistic approach to understanding these dynamics that includes plastic changes and plant community transformations and also extends beyond this single trophic level targeted by herbicides to the effects on nontarget plant-associated organisms and their potential to evolve, thereby embracing the complexity of these real-world systems. We make explicit recommendations for future research to achieve this goal and specifically address impacts of ecology on evolution, evolution on ecology and their feedbacks so that we can gain a more predictive view of the fates of herbicide-impacted communities.

Environmentally induced phenotypic plasticity and DNA methylation changes in a wild potato growing in two contrasting Andean experimental gardens.

DNA methylation can be environmentally modulated and plays a role in phenotypic plasticity. To understand the role of environmentally induced epigenetic variation and its dynamics in natural populations and ecosystems, it is relevant to place studies in a real-world context. Our experimental model is the wild potato Solanum kurtzianum, a close relative of the cultivated potato S. tuberosum. It was evaluated in its natural habitat, an arid Andean region in Argentina characterised by spatial and temporal environmental fluctuations. The dynamics of phenotypic and epigenetic variability (with Methyl Sensitive Amplified Polymorphism markers, MSAP) were assayed in three genotypes across three growing seasons. These genotypes were cultivated permanently and also reciprocally transplanted between experimental gardens (EG) differing in ca. 1000 m of altitude. In two seasons, the genotypes presented differential methylation patterns associated to the EG. In the reciprocal transplants, a rapid epigenomic remodelling occurred according to the growing season. Phenotypic plasticity, both spatial (between EGs within season) and temporal (between seasons), was detected. The epigenetic and phenotypic variability was positively correlated. The lack of an evident mitotic epigenetic memory would be a common response to short-term environmental fluctuations. Thus, the environmentally induced phenotypic and epigenetic variation could contribute to populations persistence through time. These results have implications for understanding the great ecological diversity of wild potatoes.

Effects of crude oil on plant growth and leaf anatomical structures in a common coastal plant.

Phenotypic plasticity is one mechanism that allows organisms to adapt to changing environmental conditions, and is especially important for plants since they are generally immobile. Recent anthropogenic disturbances such as oil spills have expanded the types of stressors that plants must cope with, and more work is needed to understand the extent to which plants can adapt. This study examined the physiological and anatomical responses of Ipomoea pes-caprae to crude oil, and determined its plasticity in response to crude oil. Four concentrations of crude oil (1%, 2%, 3%, and 4% v/w) were applied to experimental plants and then compared with control plants over the next 120 days. Crude oil meaningfully impacted 4 out of 5 physiological characters (survival time, leaf length, leaf width, and chlorophyll content) and 4 out of 19 anatomical characters (leaf blade thickness, leaf spongy layer height, leaf adaxial cutin thickness, and leaf abaxial cutin thickness). These results demonstrate that I. pes-caprae exhibits low anatomical plasticity in response to crude oil, resulting in reduced survival and physiological performance. Our findings highlight the importance of understanding how anthropogenic actions affect relatively immobile plants, which are not always able to cope with such stressors.

Hydrocarbonoclastic bacterial species growing on hexadecane: Implications for bioaugmentation in marine ecosystems.

LIMITATIONS: of bioaugmentation strategies are an obstacle for damage mitigation caused by oil spills in marine environments. Cells added to the contaminated sites are quickly lost by low adherence to the contaminants, rendering ineffective. This study used two hydrocarbonoclastic species - Rhodococcus rhodochrous TRN7 and Nocardia farcinica TRH1 cells - growing in mineral medium containing hexadecane to evaluate cell distribution in a crude-oil contaminated marine water. Cell affinity to hydrophobic compounds was quantified using Microbial Adhesion to Hydrocarbons test and analysis of fatty acids profile was performed using the Microbial Identification System. Bioremediation simulations were set up and cell populations of both strains were quantified by Fluorescent in situ Hybridization. R. rhodochrous and N. farcinica reached up to 97% and 60% of adhesion to hexadecane, respectively. The carbon source had more influence on the fatty acid profiles of both strains than the microbial species. The presence of 45.24% of 13:0 anteiso on total fatty acids in R. rhodochrous and 12.35% of saturated fatty acids with less than 13 carbons atoms in N. farcinica, as well as the occurrence of fatty alcohols only in presence of hexadecane in both species, are indicators that fatty acid changes are involved in the adaptation of the cells to remain at the water/oil interface. Cell quantification after bioremediation simulations revealed an increase in the density of both species, suggesting that the bioremediation strategies resulted on the increase of hydrocarbonoclastic species and up to 27.9% of all prokaryotic microbial populations in the microcosms were composed of R. rhodochrous or N. farcinica. These findings show the potential of application of these two bacterial strains in bioaugmentation of hydrocarbon-contaminated marine ecosystems.R. rhodochrous TRN7 and N. farcinica TRH1 hydrocarbonoclastic strains modify the fatty acid profile and increases density, optimizing hydrocarbons biodegradation.

Prey exclusion combined with simulated fire increases subsequent prey-capture potential in the pale pitcher plant, Sarracenia alata.

PREMISE: The association of carnivory (an adaptation to nutrient-poor soils) with fire has been described as a paradox, given increases in nutrient availability that often accompany fire. The nutrients that increase in availability following fire, however, may not be the same as those provided by prey and may not reduce nutrient limitation if accompanied by even greater increases in light. METHODS: Using a factorial experiment in the field, we examined how simulated fire (clipping plus nitrogen-free fertilizer addition) and prey-derived nutrient availability (prey exclusion) interacted to influence carnivorous potential in Sarracenia alata and belowground competition with its neighbors (manipulated via trenching). We hypothesized that simulated fire combined with prey exclusion would (1) increase the potential for prey capture relative to shade avoidance, hereafter, relative prey-capture potential (RPCP), and/or (2) increase belowground competition with neighboring plants. RESULTS: Sarracenia alata increased RPCP in response to the combination of simulated fire and prey exclusion, despite increases in phosphorus and other nutrients associated with the simulated fire treatment, suggesting that prey capture potential increases in response to increased nitrogen limitation resulting from increases in light and/or phosphorus after fire. We found no evidence of belowground competition. CONCLUSIONS: The potential importance of carnivory in Sarracenia alata increases following fire. This result helps to explain the paradoxical association of carnivorous plants with fire by demonstrating the potential for prey-derived nutrient limitation to increase rather than decrease in response to increases in light and nutrients other than nitrogen following fire.

Interactions between genetics and environment shape Camelina seed oil composition.

BACKGROUND: Camelina sativa (gold-of-pleasure) is a traditional European oilseed crop and emerging biofuel source with high levels of desirable fatty acids. A twentieth century germplasm bottleneck depleted genetic diversity in the crop, leading to recent interest in using wild relatives for crop improvement. However, little is known about seed oil content and genetic diversity in wild Camelina species. RESULTS: We used gas chromatography, environmental niche assessment, and genotyping-by-sequencing to assess seed fatty acid composition, environmental distributions, and population structure in C. sativa and four congeners, with a primary focus on the crop's wild progenitor, C. microcarpa. Fatty acid composition differed significantly between Camelina species, which occur in largely non-overlapping environments. The crop progenitor comprises three genetic subpopulations with discrete fatty acid compositions. Environment, subpopulation, and population-by-environment interactions were all important predictors for seed oil in these wild populations. A complementary growth chamber experiment using C. sativa confirmed that growing conditions can dramatically affect both oil quantity and fatty acid composition in Camelina. CONCLUSIONS: Genetics, environmental conditions, and genotype-by-environment interactions all contribute to fatty acid variation in Camelina species. These insights suggest careful breeding may overcome the unfavorable FA compositions in oilseed crops that are predicted with warming climates.

The invasive plant Solidago canadensis exhibits partial local adaptation to low salinity at germination but not at later life-history stages.

PREMISE: Evolutionary adaptation may enable plants to inhabit a broad range of environments. However, germination and early life-history stages have seldom been considered in estimates of evolutionary adaptation. Moreover, whether soil microbial communities can influence evolutionary adaptation in plants remains little explored. METHODS: We used reciprocal transplant experiments to investigate whether two populations of an invasive plant Solidago canadensis that occur in contrasting habitats of low versus high salinity expressed adaptation to the respective salinity levels. We germinated S. canadensis seeds collected from low-and high-salinity habitats under low- and high-salt treatments. We also raised S. canadensis seedlings from the two salinity habitats under low- and high-salt treatments and in the presence versus absence of microbial communities from the two habitats. RESULTS: Genotypes from a low-salinity habitat had higher germination rates under low-salt treatment than genotypes from a high-salinity habitat. However, both genotypes had similar germination rates under a high-salt treatment. The two genotypes also had similar seedling survival and biomass responses to low- and high-salt treatments. Nevertheless, seedling biomass was significantly higher under low salt treatment. Soil microbial communities did not influence biomass of S. canadensis under the two salt treatments. CONCLUSIONS: The results on germination rates suggest partial local adaptation to low salinity. However, there was no evidence of local adaptation to salinity at the seedling survival and growth stages. The finding that germination and seedling biomass responded to different salt treatments suggests that the two traits are important for salt tolerance.

Morphological variation in Cynodon dactylon (L.) Pers., and its relationship with the environment along a longitudinal gradient.

BACKGROUND: Geographical variation in morphological traits may reflect evolutionary patterns of morphological adaptability along environmental gradients. Comprehensive information on longitudinal patterns of morphological trait variation is very meaningful to explore morphological diversity and evolutionary trends in widespread bermudagrass. METHODS: To explore the spatial patterns of morphological traits, we investigated 10 morphological traits of bermudagrass and 10 soil nutrient indexes and collected local climate data for 13 different regions from 119°E to 105°E along the latitude 34°N. RESULTS: Considerable variations in morphological traits were observed at different longitudes, and the variations in most of the evaluated traits within populations were lower than those among populations. All of the 13 different longitudinal sites were divided into three groups based on morphological traits by cluster analysis. The major sources of diversity at the different longitudes were leaf length of the erect shoot, leaf width of the erect shoot, and the internode lengths of the erect shoot and stolon as determined by principal component analysis. Pearson correlation analysis also indicated that longitude was significantly and negatively correlated with these traits as well. Mean average rainfall was significantly correlated with leaf length of the erect shoot and the internode lengths of the erect shoot and stolon, while mean average temperature was only significantly correlated with internode length of the erect shoots. Available sulfur was significantly correlated with internode length of the erect shoot, plant height, and reproductive branch height, while the exchangeable Ca was significantly correlated with internode lengths of the erect shoot and stolon. Soil pH was significantly correlated with the internode length of the stolon. Longitude is an important factor that affects morphological trait variation in wild bermudagrass, and the leaves of the erect shoot and the internode length enlarged significantly with the collection sites moving from east to west. CONCLUSION: Different combinations and interactions of environmental factors (soil and climate) along a longitudinal gradient may have strong effects on one or more morphological traits of bermudagrass.

Functional ecology of congeneric variation in the leaf economics spectrum.

Variation in resource availability can lead to phenotypic plasticity in the traits comprising the world-wide leaf economics spectrum (LES), potentially impairing plant function and complicating the use of tabulated values for LES traits in ecological studies. We compared 14 Carex (Cyperaceae) species in a factorial experiment (unshaded/shaded × sufficient/insufficient P) to analyze how changes in the network of allometric scaling relationships among LES traits influenced growth under favorable and resource-limited conditions. Changes in leaf mass per area (LMA) shifted the scaling relationships among LES traits expressed per unit area vs mass in ways that helped to sustain growth under resource limitation. Increases in area-normalized photosynthetic capacity and foliar nitrogen (N) were correlated with increased growth, offsetting losses associated with mass-normalized dark respiration and foliar N. These shifts increased the contributions to growth associated with photosynthetic N-use efficiency and the N : P ratio. Plasticity in LMA is at the hub of the functional role of the LES as an integrated and resilient complex system that balances the relationships among area- and mass-based aspects of gas exchange and foliar nutrient traits to sustain at least some degree of plant growth under differing availabilities of above- and below-ground resources.