Abstract Mosses dominate ground cover in many ecosystems and are central to carbon and nutrient cycling, water regulation, and surface energy balance. Their poikilohydric physiology, without stomatal control or vascular transport, couples metabolism closely to moisture. While climate extremes affecting moisture become more frequent, how drought and rewetting affect volatile organic compound (VOC) emissions from mosses remains poorly understood. This study examined how a heatwave-associated drought and subsequent rewetting affected VOC emission rates and blend compositions in the moss Tomentypnum nitens. Subarctic heath mesocosms containing T. nitens were maintained in climate chambers during a pre drought period and exposed sequentially to a three-week heatwave-associated drought, and one week rewetting treatment. Moss shoots detached from mesocosms were enclosed in a gas-exchange cuvette to measure VOC emissions analyzed by GC-MS, net photosynthesis and evaporation rates. Tissue water content was also determined. Drought strongly reduced water content and evaporation and shifted net photosynthesis from positive to negative values. Total VOC emissions declined by 90% in response to drought and recovered after rewetting (p = 0.06). Drought also shifted the VOC blend toward hydrocarbon dominance (nearly 80% of total). After rewetting, the blend contained a greater proportion of oxygenated VOCs and a smaller proportion of sesquiterpenes than before drought. The legacy effects of drought on VOC blend may influence both the ecological roles of moss VOCs and their contribution to biosphere-atmosphere interactions.
Abstract The invasive plant species, Erigeron canadensis L., exhibits a propensity to colonize heavy metal-contaminated areas. However, its molecular adaptation mechanisms to heavy metals remain poorly understood. This study explored its adaptive mechanisms under combined cadmium (Cd) and lead (Pb) stress by investigating growth performance, heavy metal accumulation, and root molecular responses. Aboveground growth of E. canadensis was unaffected by any treatment, whereas root biomass was reduced only under high-concentration combined Cd and Pb stress. Cd and Pb were predominantly accumulated in roots instead of aboveground tissues. Notably, a translocation factor (TF) > 1 for Cd implied that E. canadensis actively accumulated Cd in roots and translocated it to aerial parts. However, a TF < 1 for Pb suggested that this species employed an exclusion strategy to mitigate Pb stress. Differentially expressed genes (DEGs) in E. canadensis roots were primarily involved in transport, signal transduction, antioxidant defense, transcription regulation, and ribosome function under heavy metal stress. Zinc transporter ZntB was verified to mediate Cd uptake and tolerance, while natural resistance-associated macrophage protein 3 and cyclic nucleotide-gated ion channel 2 were shown to mediate Cd and Pb uptake and tolerance by heterologous expression in yeast. Up-regulated amino acid, sugar, and auxin transporters together with ribosomal proteins may contribute to the maintenance of nutrient supply, auxin homeostasis, and protein synthesis for normal root growth. High-level metal stress triggered more extensive down-regulated of ROS-associated genes in E. canadensis roots. These findings provide root-specific molecular insights into the E. canadensis adaptation to heavy metal stress.
Abstract Background and Aims Pollinators facilitate the reproduction of most wild plants. Declines in pollinator populations have led to interest in establishing floral enhancements to support them. However, knowledge about how food rewards vary across plant species planted to support pollinators remains scant. Methods Using a greenhouse common garden, we quantified nectar volume, nectar sucrose, and pollen protein quantity for 11 species commonly planted to support pollinators in Mediterranean climates. We evaluated if variation was explained by life history and the potential for tradeoffs between nectar and pollen quality. Key Results There was high variation in nectar and moderate variation in pollen protein across species. The probability of producing nectar was higher for perennial plants. For flowers that contained nectar, there were no differences between annual and perennial plants in nectar traits. The species that produced the highest quality nectar (Scrophularia californica) produced pollen with the lowest protein amounts, and the species that produced the lowest quality nectar (Madia elegans) produced pollen with the highest protein amounts. There was no statistical association between pollen protein amounts and nectar traits across species. Conclusions The nutrition pollinators obtain from foraging on most species studied here may come primarily in the form of carbohydrates or protein, but not both. However, one species (Epilobium canum) produced both high-quality nectar and pollen, so identifying others that produce similarly broad, high-quality rewards would be worthwhile. Our results also suggest that including perennial plants in pollinator gardens will facilitate pollinator acquisition of carbohydrates.
Abstract Rhexia (Melastomataceae), a temperate genus composed of 13 species in eastern North America, provides a useful system for evaluating how taxonomic and cytogenetic complexity influence forecasts of climate-driven habitat suitability distribution. Ecological niche models incorporating climatic and edaphic variables were used to estimate current and future habitat suitability for diploid, polyploid, and mixed-cytotype species. Habitat suitability was strongly associated with soil texture, hydrological conditions, and precipitation, with suitable environments characterized by sandy, acidic, and seasonally moist habitats. Projections under future climate scenarios revealed highly variable, species-specific responses, with some taxa exhibiting substantial expansions in the distribution of suitable habitat and others experiencing pronounced contractions. Contrary to expectations, ploidal level was not consistently associated with niche breadth or climate response, as both diploid and polyploid species displayed a wide range of outcomes. These findings highlight the need for flexible, habitat-focused conservation strategies that consider hydrological and edaphic variables and demonstrate how taxonomic and cytogenetic complexity can complicate forecasts of biodiversity change under future climate scenarios.
Abstract Different gall morphotypes reflect the reactivity of host plants and the specificity of their interactions with gall-inducing organisms. Gall structure is functionally divided into internal and external tissue compartments, which play nutritional and protective roles, respectively. We propose that gall structure is functionally responsive to environmental gradients, with a trade-off between investment in external and internal compartments that varies consistently with environmental cues. Furthermore, we also expect to identify patterns in the expression of anatomical traits across different environments. We compiled literature data on the anatomy and structure of Neotropical galls, standardized gall traits, and quantified tissue investment in each compartment using a Tissue Investment Index (TII). Then, we applied multivariate methods and hierarchical clustering to classify morphotypes into distinct morphofunctional profiles, followed by redundancy analysis and generalized linear models to relate these profiles to climatic variables. Anatomical traits were distributed across broad morphofunctional groups oriented towards protection or nutrition, with humidity and solar radiation emerging as the environmental variables most consistently associated with morphoanatomical variation, together explaining approximately 16% of total trait variation. Humidity was primarily associated with the degree of cellular hypertrophy and hyperplasia and with investment in the internal compartment, which was relatively higher under greater water availability. Solar radiation was associated with parenchyma homogenization and epidermal thickness, traits linked to water retention and metabolic capacity under higher irradiance. These patterns were consistent across diverse plant–gall systems, suggesting that gall anatomical traits respond to environmental gradients and may serve as informative indicators of habitat conditions.
