Ecophysiological Strategies Research Articles

Behind the Loss of Salinity Resistance during Domestication: Alternative Eco-Physiological Strategies Are Revealed in Tomato Clade

Salinity stress impairs growth and physiological performance in tomato, which is one of the most economically important vegetables and is widely cultivated in arid and semi-arid areas of the world. Plant landraces, which are heterogeneous, local adaptations of domesticated species, offer a unique opportunity to valorize available germplasm, underpinning the productivity, resilience, and adaptive capacity of staple crops in vulnerable environments. Here, we investigated the response of fully mature tomato plants from a commercial variety, an ancestral wild relative, and a landrace under short-term salinity exposure, as well as their ability to recover upon cessation of stress. The heterogeneous panel evaluated in this study revealed different adaptative strategies to cope the stress. Our data highlighted the ability of the tomato clade to handle low and intermediate salinity stress for short-term exposure time, as well as its capacity to recover after the cessation of stress, although inter- and intraspecific variations in morphological and physiological responses to salinity were observed. Overall, the landrace and the wild type performed similarly to control conditions under low salinity, demonstrating an improved ability to maintain ionic balance. In contrast, the commercial genotype showed susceptibility and severe symptoms even under low salinity, with pronounced reductions in K+/Na+ ratio, PSII photochemical efficiency, and photosynthetic pigments. This research confirmed that improved salt tolerant genotypes can lead to substantial, positive impacts on horticultural production. While the salt tolerance mechanism of domesticated tomato was efficient under mild stress conditions, it failed at higher salinity levels.

Deciphering of the morpho-physiological traits of two native grasses from Argentina with contrasting drought resistance strategies

Context Semiarid environments, such as the Patagonian shrublands, are characterised by having shrubby patches surrounded by grasses with different ecophysiological strategies to tolerate long dry periods. Aims We hypothesised that coexisting grasses of the Patagonian rangeland, already classified as drought-escaping or drought-tolerant, have different traits according to the season and the annual rainfall events. Methods Two dominant native grasses were selected: Pappostipa speciosa (evergreen) and Poa ligularis (deciduous). Samples were collected in the four seasons for the term of 1 year. Rainfall events and soil water content of each season were determined. Spring was the wettest season and autumn the driest. Physiological (relative water content, pigments, hormones), biochemical (polyphenols, antioxidant activity) and morphological traits were measured in the four seasons. Key results P. speciosa was characterised by keeping evergreen leaves with high production of polyphenols as secondary metabolites with high antioxidant capacity during the dry autumn and winter seasons. P. ligularis was characterised by high contents of gibberellin (GA1), auxin (IAA), total phenols, total flavonoids and tartaric acid esters, and high antioxidant capacity in roots during the autumn dry season. In addition, P. ligularis leaves had higher content of carotenoids and polyphenols than P. speciosa during the summer dry season. Conclusions The major adaptive strategy to tolerate dry periods is the high activity of the secondary metabolism, mainly in leaves in P. speciosa (a drought-tolerant grass) and in roots in P. ligularis (a drought-escaping grass). Implications Rainfall variations during a year can affect the phenological growth stages and the metabolism of two native grasses from Argentina characterised by different drought resistance mechanisms.

Functional responses to multiple sequential abiotic stress (waterlogging-drought) in three woody taxa with different root systems and stress tolerance.

There is generally a trade-off in the resistance to drought and to waterlogging. However, several species are sequentially subjected to both stressors in many environments. We evaluated the ecophysiological strategies to cope with multiple sequential stress of waterlogging and drought (W + D) of three taxa differing in stress resistance and root morphology: the phreatophic Eucalyptus camaldulensis (Ec) and two shallow-rooted willow clones: Salix matsudana x Salix alba (SmxSa) and Salix nigra (Sn4). Individuals of the three taxa were grown in pots and assigned to either of four treatments: Control (well-watered plants), well-watered followed by drought (C + D); waterlogged for 15 days followed by drought (W15d + D) and waterlogged for 30 days followed by drought (W30d + D). Biomass allocation, growth (diameter, height, length of leaves, and roots), specific leaf area, stomatal conductance, water potential, hydraulic conductivity of roots and branches, leaf C13 and root cortical aerenchyma formation were determined at different stages of the experiment. Ec growth was not affected by W + D, developing tolerance strategies at leaf and whole plant levels. Differential effects of W + D were observed in both Salix clones depending on the time of waterlogging. In Sn4 and SmxSa, the root biomass was affected in W15d + D treatment, but a root tolerance response (aerenchyma and adventitious root formation) was observed in W30d + D. In the three taxa, and contrary to expectations, the previous exposure to a waterlogging period did not increase the susceptibility of the plants to a subsequent drought event. On the contrary, we found tolerance, which depended on the time of waterlogging exposure.

Long-term weathering difference in soil-like indicators of bauxite residue mediates the multifunctionality driven by microbial communities

Long-term weathering enhances the stability of ecosystem services and alters the microbiome, however, its influences on the relationship between microbial diversity and multifunctionality are still poorly understood. Hereby, 156 samples (0–20 cm) from five artificially divided functional zones including central bauxite residue zone (BR), the zone near residential area (RA), the zone near dry farming area (DR), the zone near natural forest area (NF), and the zone near grassland and forest area (GF) were collected in a typical disposal area to determine the heterogeneity and development of biotic and abiotic properties of bauxite residue. Residues in BR and RA exhibited higher values of pH, EC, heavy metals, and exchangeable sodium percentage compared to those in NF and GF. Our results showed a positive correlation between multifunctionality and soil-like quality during long-term weathering. Microbial diversity and microbial network complexity responded positively to multifunctionality within the microbial community, which was parallel with ecosystem functioning. Long-term weathering promoted oligotrophs-dominated bacterial assemblages (mostly Acidobacteria and Chloroflexi) and suppressed copiotrophs (including Proteobacteria and Bacteroidota), while the response of fungal communities was lower. Rare taxa from bacterial oligotrophs were particularly important at the current stage for maintaining ecosystem services and ensuring microbial network complexity. Our results underscore the significance of microbial ecophysiological strategies in response to changes in multifunctionality during long-term weathering, and highlight the necessity of conserving and augmenting the abundance of rare taxa to ensure the stable provision of ecosystem functions in bauxite residue disposal areas.

Physiological but not morphological adjustments along latitudinal gradients in a human commensal species, the Eurasian tree sparrow.

Human commensal species take advantage of anthropogenic conditions that are less likely to be challenged by the selective pressures of natural environments. Their morphological and physiological phenotypes can therefore dissociate from habitat characteristics. Understanding how these species adjust their morphological and physiological traits across latitudinal gradients is fundamental to uncovering the eco-physiological strategies underlying coping mechanisms. Here, we studied morphological traits in breeding Eurasian tree sparrows (ETSs; Passer montanus) among low-latitude (Yunnan and Hunan) and middle-latitude (Hebei) localities in China. We then compared body mass, lengths of bill, tarsometatarsus, wing, total body, and tail feather, baseline and capture stress-induced levels of plasma corticosterone (CORT) and the metabolites including glucose (Glu), total triglyceride (TG), free fatty acid (FFA), total protein (TP), and uric acid (UA). None of the measured morphological parameters varied with latitude except in the Hunan population, which demonstrated longer bills than those in other populations. Stress-induced CORT levels significantly exceeded baseline levels and decreased with increasing latitude, but total integrated CORT levels did not vary with latitude. Capture stress induced significantly increased Glu levels and decreased TG levels, independent of site. However, the Hunan population had significantly higher baseline CORT, baseline and stress-induced FFA levels but lower UA levels, which differed from other populations. Our results suggest that rather than morphological adjustments, physiological adjustments are mainly involved in coping mechanisms for middle-latitude adaptation in ETSs. It is worth investigating whether other avian species also exhibit such dissociation from external morphological designs while depending on physiological adjustments. This article is protected by copyright. All rights reserved.

Tropical shrubs living in an extreme environment show convergent ecological strategies but divergent ecophysiological strategies.

Trait-based frameworks assess plant survival strategies using different approaches. Some frameworks use functional traits to assign species to a priori defined ecological strategies. Others use functional traits as the central element of a species ecophysiological strategy. We compared these two approaches by asking: (1) what is the primary ecological strategy of three dominant co-occurring shrub species from inselbergs based on the CSR scheme, and (2) what main functional traits characterize the ecophysiological strategy of the species based on their use of carbon, water and light? We conducted our study on a Colombian inselberg. In this extreme environment with multiple stressors (high temperatures and low resource availability), we expected all species to be stress tolerant (S in the CSR scheme) and have similar ecophysiological strategies. We measured 22 anatomical, morphological and physiological leaf traits. The three species have convergent ecological strategies as measured by CSR (S, Acanthella sprucei; and S/CS, Mandevilla lancifolia and Tabebuia orinocensis) yet divergent resource-use strategies as measured by their functional traits. A. sprucei has the most conservative carbon use, risky water use and a shade-tolerant strategy. M. lancifolia has acquisitive carbon use, safe water use and a shade-tolerant strategy. T. orinocensis has intermediate carbon use, safe water use and a light-demanding strategy. Additionally, stomatal traits that are easy to measure are valuable to describe resource-use strategies because they are highly correlated with two physiological functions that are hard to measure: stomatal conductance and maximum photosynthesis per unit mass. The two approaches provide complementary information on species strategies. Plant species can co-occur in extreme environments, such as inselbergs, because they exhibit convergent primary ecological strategies but divergent ecophysiological strategies, allowing them to use limiting resources differently.

Long-term organic fertilization promotes the resilience of soil multifunctionality driven by bacterial communities

Long-term intensive fertilization is a practice common around the world and gradually alters soil microbiome, however, its influences on the temporal resilience of soil multifunctionality to biodiversity loss and biodiversity-multifunctionality relationships remain poorly understood. Here, we manipulated soil biodiversity using the dilution-to-extinction approach to examine the temporal variability in individual functions, soil multifunctionality and their relationships with bacterial and fungal communities under different fertilization treatments during a 90-day re-colonization process. We found that organic fertilization accelerated the resilience of single functions and soil multifunctionality to biodiversity loss compared with mineral fertilization and unfertilized control. The fungal community was less resilient than bacterial community to disturbances caused by fertilization and dilution. Bacterial but not fungal diversity was significantly and positively related to multifunctionality, and the strength of the diversity-multifunctionality relationships in organic fertilized soil was 3- and 67-fold higher than that in unfertilized and mineral fertilized soil, respectively. Both organic and mineral nutrient inputs promoted copiotroph-dominated bacterial assemblages (including Proteobacteria and Bacteroidetes members) and suppressed oligotrophs (mostly Acidobacteria and Chloroflexi), which paralleled multifunctionality resilience patterns in fertilized soils. β-Diversity of bacterial copiotrophs alone or in combination was significantly related to changes in multifunctionality. Random forest analysis and structural equation modeling indicated that bacterial community diversity and composition along with soil carbon and nitrogen basically determined soil multifunctionality, with 70% of the variance in multifunctionality being explained. Rare taxa from the bacterial copiotrophs were particularly important for maintaining multifunctionality. Our results underline the importance of fertilization-induced shifts in microbial ecophysiological strategies for promoting the resilience of soil multifunctionality to biodiversity loss, and the need to preserve the diversity of rare copiotrophic taxa for stable provision of ecosystem functions under future environmental change.

Ecomorphosis in European Collembola: A review in the context of trait-based ecology

Collembola are a widespread class of arthropods that live mostly in the soil or on its surface. Communities of Collembola have notably been used as bioindicators of several environmental factors such as pollution or land use. Recently, they have also opened perspectives for monitoring the effects of projected climate change on soil biodiversity, in particular through the responses of their traits. Collembola are known to exhibit several morphological variations throughout their lifecycle (other than growth and sexual dimorphism). One of these phenomena, ecomorphosis, has been described as a survival strategy mainly triggered by elevated temperature. This could be of interest in analysing collembolan adaptation to climate change, yet studies on this are - to date - sparse in international literature in English. To begin to address this gap, we conducted a literature review that enabled us to: (i) identify the concepts behind the ecomorphosis strategy, (ii) list the collembolan species known to display ecomorphosis, (iii) summarize its consequences on individuals; and (iv) analyse its theoretical implications for community ecology and functional ecology. We then discussed its potential use as a proxy for climate adversity. We thus suggested using the ability of a species to display ecomorphosis as a trait, and in the future test its responses in collembolan communities along climatic gradients. Considering the recent inputs of taking into account intraspecific trait variability in community ecology, we advocate for a better understanding of such eco-physiological strategies in order to improve our hypotheses-based approaches in trait-environment relationships. In a context of rapid global climate change, our findings may provide insights into functional responses to climatic gradients in Collembola, and hopefully contribute to stimulate discussion in other soil fauna biological models.

Biogeographical patterns of community-level content of N and P and their stoichiometric ratios in subtropical forest floor bryophytes

• Biogeographical patterns of nutrients for bryophytes remain largely unknown. • Relationships between bryophyte nutrients and environmental factors were calculated. • Bryophyte N and P content increased with increasing elevations and decreasing MAT. • Nutrient content of bryophytes and those of soil were positively associated. • Soil nutrient content and MAT were more important determinants of bryophyte N and P. With special phylogenetic status, life history, morphology, adaptations, and ecophysiological strategies, bryophytes differ from vascular plants in terms of the requirement, uptake, allocation, and releasing rate of nutrients. However, biogeographical patterns of nutrients for bryophytes remain largely unknown. The present study determined and calculated the community-level carbon (C), nitrogen (N), and phosphorus (P) content and their stoichiometric ratios of the photosynthetic tissues of the subtropical forest-floor bryophytes collected from 295 sites in Sichuan province, China. We aimed to find out: 1) the geographical patterns in the content of N and P and the stoichiometric ratio of N to P for bryophytes; 2) the effects of environmental factors (climate, soil nutrient content, and stand attributes); and 3) the driving factors. We found that the bryophytes collected from the western plateau had a higher P content and a lower N:P than those from the eastern basin. The bryophytes’ N and P content generally increased with increasing elevations and decreasing mean annual temperature (MAT) and potential evaporation, while the N:P ratio decreased with decreasing elevations. But these patterns were scale-dependent. Nutrient content of bryophytes and those of soil were positively associated. Bryophyte N content was unrelated to mean annual precipitation (MAP) and stand attributes, while P content was negatively related to MAP and shrub and herb cover. Among the environmental factors at play, soil nutrient content and MAT were more important determinants of bryophyte N and P content than MAP and stand attributes. This study contributes to a better understanding of the relationships among environmental factors and bryophyte N and P at a basin-mountain transition zone and provides evidence to quantitatively assess the ecological role of bryophytes in nutrient cycling in the ecosystem.

Pelagic and ice‐associated microalgae under elevated light and pCO2: Contrasting physiological strategies in two Arctic diatoms

AbstractSea ice retreat, changing stratification, and ocean acidification are fundamentally changing the light availability and physico‐chemical conditions for primary producers in the Arctic Ocean. However, detailed studies on ecophysiological strategies and performance of key species in the pelagic and ice‐associated habitat remain scarce. Therefore, we investigated the acclimated responses of the diatoms Thalassiosira hyalina and Melosira arctica toward elevated irradiance and CO2 partial pressures (pCO2). Next to growth, elemental composition, and biomass production, we assessed detailed photophysiological responses through fluorometry and gas‐flux measurements, including respiration and carbon acquisition. In the pelagic T. hyalina, growth rates remained high in all treatments and biomass production increased strongly with light. Even under low irradiances cells maintained a high‐light acclimated state, allowing them to opportunistically utilize high irradiances by means of a highly plastic photosynthetic machinery and carbon uptake. The ice‐associated M. arctica proved to be less plastic and more specialized on low‐light. Its acclimation to high irradiances was characterized by minimizing photon harvest and photosynthetic efficiency, which led to lowered growth. Comparably low growth rates and strong silification advocate a strategy of persistence rather than of fast proliferation, which is also in line with the observed formation of resting stages under low‐light conditions. In both species, responses to elevated pCO2 were comparably minor. Although both diatom species persisted under the applied conditions, their competitive abilities and strategies differ strongly. With the anticipated extension of Arctic pelagic habitats, flexible high‐light specialists like T. hyalina seem to face a brighter future.

Effects of NaCl and CaCl2 Salinization on Morpho-Anatomical and Physiological Traits of Potted Callistemon citrinus Plants

The aim of this work was to assess the possible coordination mechanisms between leaf functional anatomical traits and physiological acclimation of potted Callistemon citrinus plants when subjected to two saline iso-osmotic solutions using NaCl or CaCl2. Digital image analysis was applied to quantify anatomical parameters with a specific focus on the occurrence of signs of structural damage as well as on alterations, such as the occurrence of shrunk tissues and accumulation of phenolic compounds. Morpho-anatomical analyses were accompanied by measurements of leaf gas exchange and chlorophyll fluorescence emission. Results showed that C. citrinus plants, when irrigated with the CaCl2 solution, induced a leaf morpho-anatomical structure which did not allow the maintenance of high photosynthetic performance under such conditions, compared to both controls and plants treated with the iso-osmotic solution of NaCl. Data collected seem to suggest a close relationship between anatomical traits and eco-physiological strategies in maintaining the photosynthetic efficiency under saline stress conditions and highlight the fundamental role of leaf anatomy in imposing the limits of plant physiology.

Population and reproductive structure in the endangered and highly endemic freshwater crab Aegla concepcionensis (Decapoda:Pleocyemata:Aeglidae) from Chile

AbstractPopulation and reproductive information of highly endemic species allow us to understand their underlying conservation problems. Aegla concepcionensis is restricted to a small and intervened Chilean basin, and its conservation status has varied from extinct in nature to endangered. We characterized their life history measuring population, morphological and environmental variables during an annual cycle capturing individuals with a catch and release method based on electroshocking. Although the maximum water temperature was related to the recruitment, it can be physiologically risky for the remaining macroinvertebrate community. The relationship between abundance and narrow pH variations indicates a condition of unstable equilibrium given the environmental deterioration by deforestation. Sex ratio was predominantly male biased during copulatory activity, and sexually dimorphic body size distributions supported the hypothesis of greater natural selection in females and sexual selection in males. The period of ovigerous females was comparatively restricted, late and consistent with an efficient ecophysiological strategy of reproductive investment. Patterns of pubertal moult, onset of morphometric maturity, absence of morphological differentiation in both sexes suggested that A. concepcionensis tends to maximize reproductive performance favouring the recovery of their relict populations.

Phenotypic Diversity and Plasticity of Photoresponse Across an Environmentally Contrasting Family of Phytoflagellates.

Organisms often employ ecophysiological strategies to exploit environmental conditions and ensure bio-energetic success. However, the many complexities involved in the differential expression and flexibility of these strategies are rarely fully understood. Therefore, for the first time, using a three-part cross-disciplinary laboratory experimental analysis, we investigated the diversity and plasticity of photoresponsive traits employed by one family of environmentally contrasting, ecologically important phytoflagellates. The results demonstrated an extensive inter-species phenotypic diversity of behavioural, physiological, and compositional photoresponse across the Chlamydomonadaceae, and a multifaceted intra-species phenotypic plasticity, involving a broad range of beneficial photoacclimation strategies, often attributable to environmental predisposition and phylogenetic differentiation. Deceptively diverse and sophisticated strong (population and individual cell) behavioural photoresponses were observed, with divergence from a general preference for low light (and flexibility) dictated by intra-familial differences in typical habitat (salinity and trophy) and phylogeny. Notably, contrasting lower, narrow, and flexible compared with higher, broad, and stable preferences were observed in freshwater vs. brackish and marine species. Complex diversity and plasticity in physiological and compositional photoresponses were also discovered. Metabolic characteristics (such as growth rates, respiratory costs and photosynthetic capacity, efficiency, compensation and saturation points) varied elaborately with species, typical habitat (often varying more in eutrophic species, such as Chlamydomonas reinhardtii), and culture irradiance (adjusting to optimise energy acquisition and suggesting some propensity for low light). Considerable variations in intracellular pigment and biochemical composition were also recorded. Photosynthetic and accessory pigments (such as chlorophyll a, xanthophyll-cycle components, chlorophyll a:b and chlorophyll a:carotenoid ratios, fatty acid content and saturation ratios) varied with phylogeny and typical habitat (to attune photosystem ratios in different trophic conditions and to optimise shade adaptation, photoprotection, and thylakoid architecture, particularly in freshwater environments), and changed with irradiance (as reaction and harvesting centres adjusted to modulate absorption and quantum yield). The complex, concomitant nature of the results also advocated an integrative approach in future investigations. Overall, these nuanced, diverse, and flexible photoresponsive traits will greatly contribute to the functional ecology of these organisms, addressing environmental heterogeneity and potentially shaping individual fitness, spatial and temporal distribution, prevalence, and ecosystem dynamics.

Does growth rate affect diatom compositional response to temperature?

ABSTRACT Temperature is one of the environmental factors that most strongly influence the life of microalgae, from the enzymatic level up to the modification of biosynthetic and degradation potential and, thus, cellular composition. When exposed to a change in environmental milieu two main responses can be attained by cells: acclimation or homoeostasis. Recent studies testing the impact of other environmental factors indicated that the choice between these strategies is related to growth rates, i.e. cells dividing at a faster rate showed inclination to acclimation while cells dividing at a slower rate were more prone to homoeostasis. These findings motivated us to further explore the extent to which these compositional response modes are applied under varying temperature. Two representative marine diatoms, one centric, Thalassiosira pseudonana, and one pennate, Cylindrotheca fusiformis were investigated. Species were cultured at 15°C, 20°C and 30°C and at two growth rates. Compositional response was analysed with respect to elemental stoichiometry (carbon, nitrogen, silica, phosphorus, sulphur, manganese, iron, zinc and copper) and the major organic pool ratios (carbohydrate:lipid, carbohydrate:protein and protein:lipid). While T. pseudonana exhibited an acclimation response to temperature, C. fusiformis proved to be strongly homoeostatic. In the case of T. pseudonana, our data showed that the variations in composition were consistent with the growth rate dependence hypothesis for many micronutrients, but not for carbon and nitrogen contents, and C:N ratio. These species-specific differences in response mode highlight the diversity in ecophysiological strategies of diatoms, which needs to be considered when predicting climate change responses.

Insights into the functional ecology of páramo plants in Colombia

AbstractPáramos are exceptionally species‐rich tropical alpine ecosystems that provide several important ecosystem services, including carbon storage and water provision. The responses of páramo plant species to climatic change are largely unknown, but classifying species by functional type and ecological strategy can help reduce complexity for modeling and conservation efforts. We measured 22 traits in 42 plant species with various growth forms in the Colombian Andes. We classified plant ecological strategies using CSR (C: competitor, S: stress tolerator, and R: ruderal) analysis and identified plant functional types (PFTs) using hierarchical clustering of principal components. Additionally, we calculated the functional originality of each species to identify species with unique trait combinations. We identified a high degree of convergence among traits and strategies, with most species characterized by the S and SC strategies. Considering the full set of traits, only three PFTs were identified: one composed of forbs and shrubs with tender leaves (PFT1), another composed only of species with rosettes form (PFT2), and a third composed of shrubs with tough leaves (PFT3). Values of functional originality were generally low, suggesting high redundancy in plant traits. PFT2 species, mostly rosettes, exhibited the highest functional originality of all the groups. Our results imply the existence of a limited set of ecophysiological strategies in the páramos, likely driven by the extremely stressful conditions in these systems. This functional redundancy may indicate heightened vulnerability to environmental changes; however, the presence of multiple species with shared functional traits could provide some resilience to disturbance.Abstract in Spanish is available with online material.

Transition in multi-dimensional leaf traits and their controls on water use strategies of co-occurring species along a soil limiting-resource gradient

Water use efficiency is among the most important eco-physiological strategies for species adaptation to water-limiting habitats. However, understanding of how co-occurring species adopt diverse water use strategies to cope with water- and resource-limited soil habitats via the adaptation of leaf functional traits remains limited. Here, leaf δ13C and δ18O were used as proxies for water use efficiency (WUE) and stomatal conductance (gs) across a soil limiting-resource gradient from a non-karst primary forest to karst communities including primary forest, secondary forest, shrubland, and grassland. Leaf apparent morphology, stomatal morphology, macro- and micro-nutrients and stoichiometry were measured. We found that there were significant differences in soil physical and chemical properties across five communities, forming a soil limiting-resource gradient. Co-occurring species in each community segregated along a continuous and wide range of WUE and gs, revealing a wide spectrum of stomatal regulation intensity and contrasting water use strategies. Multiple leaf functional traits separated into two principal components: leaf economics spectrum (LES) and leaf limiting-resource spectrum (LLRS). As the stress intensity of soil limiting-resource increases, the number of composition traits of LLRS increased and the dominant traits of LLRS shifted from leaf-thickness to macro-nutrients. The major driver of gs variability in each community was LES. Variability in WUE in forests was mainly determined by LES, in shrubland by LLRS, and in grassland by neither LES nor LLRS. Our study illustrated for the first time how soil limiting-resource induced changes in multi-dimensional leaf traits with effects on water use strategies of co-occurring species: the variability in WUE was mainly controlled by the leaf economic spectrum in mild soil limiting-resource habitats; however, that effect was replaced or offset by leaf limiting-resource spectrum in moderate or severe soil limiting-resource habitats.

Ecophysiological Strategies of Cedrela fissilis Vell. Seedlings under Conditions of Flooding and Light Availability

ABSTRACT Soil water availability and light are abiotic factors that may be plant stressors when they are subjected to unfavorable conditions and may limit their metabolism and trigger protection mechanisms. The aim of this study was to evaluate morphological and metabolic strategies in Cedrela fissilis seedlings that enable their survival and resilience when subjected to flooding and shading. The seedlings were cultivated under flooding for 0, 10, 20, 30, and 40 days or received only rainwater (control: 120 mm distributed over 35 evaluation days with a daily maximum of 28 mm). Flooding treatments were conducted under 70%, 30%, and 0% shading. Cedrela fissilis seedlings presented plasticity in physiological and morphological responses to flooding and shading, which indicates that this species has the potential for survival in the evaluated environments. The seedlings were tolerant to flooding for up to 40 days, regardless of light availability, although 70% shading minimized the stressful effects of flooding. The formation of lenticels, adventitious roots, and the increased activity of antioxidant enzymes from the 20th day of flooding favored the resilience of photosynthetic metabolism.

Microbial eco-physiological strategies for salinity-mediated crude oil biodegradation

Salinity variability strongly affects the behaviors of oil degrading bacteria for spilled oil biodegradation in the marine environment. However, limited studies explored the strategies of microbes on salinity-mediated crude oil biodegradation. In this study, a halotolerant bio-emulsifier producer, Exiguobacterium sp. N41P, was examined as a model strain for Alaska North Slope (ANS) crude oil (0.5%, v/v) biodegradation. Results indicated that Exiguobacterium sp. N41P could tolerant a wide range of salinity (0–120 g/L NaCl) and achieve the highest degradation efficiency under the salinity of 15 g/L NaCl due to the highest biofilm formation ability. Moreover, increased salinity induced decreased cell surface hydrophobicity and a migration of microbial growth from oil phase to aqueous phase, leading to limited bio-emulsifier productivity and depressed degradation of insoluble long-chain n-alkanes while enhancing the degradation of relative soluble naphthalene. Research findings illustrated the microbial eco-physiological mechanism for spilled oil biodegradation under diverse salinities and advanced the understanding of sophisticated marine crude oil biodegradation process.

Are underground organs able to store water and nutrients? A study case in non-arboreal species from the Brazilian Cerrado

In seasonal systems, species have specific traits to deal with water shortage. This is the case for plants in Neotropical savannas, where the dry season can endure 3 to 5 months without rain. Ecophysiological strategies to deal with the dry period are well known for savanna trees, however little is known for non-arboreal species such herbs and subshrubs concerning their water use strategies. In this study we analyzed traits related to water and nutrient storage in underground organs and leaves of non-arboreal Cerrado (Neotropical savanna of Brazil) plants. We hypothesized that underground organs are able to retain water and nutrients allowing non-arboreal plants to resprout even during water shortage. We measured wood density (WD) and saturated water content (SWC) in underground organs of 15 species differing in their growth form (5 herbs, 5 subshrubs and 5 shrubs). We also measured macronutrients concentration in underground organs and leaves of these species. We tested relationships between WD and SWC and between concentrations of underground and leaf macronutrients. We found that WD and SWC are negatively related, and that herbs showed the lowest WD, but the highest capacity to store water (higher SWC). We did not find any significant difference concerning nutrient content in underground organs and leaves among the growth forms; however, the leaf nutrient content was positively affected by the nutrient content in underground organs for N, K and Ca. We conclude that underground organs may have an important role on storing water and nutrients in savanna herbaceous species, which will promote their resprout even during the dry period.

Integrated metabolic strategy: A framework for predicting the evolution of carbon‐water tradeoffs within plant clades

Abstract The fundamental tradeoff between carbon gain and water loss has long been predicted as an evolutionary driver of plant strategies across environments. Nonetheless, challenges in measuring carbon gain and water loss in ways that integrate over leaf lifetime have limited our understanding of the variation in and mechanistic bases of this tradeoff. Furthermore, the microevolution of plant traits within species versus the macroevolution of strategies among closely related species may not be the same, and accordingly, the latter must be addressed using comparative phylogenetic analyses. Here we introduce the concept of ‘integrated metabolic strategy’ (IMS) to describe the ratio between carbon isotope composition (δ13C) and oxygen isotope composition above source water (Δ18O) of leaf cellulose. IMS is a measure of leaf‐level conditions that integrate several mechanisms contributing to carbon gain (δ13C) and water loss (Δ18O) over leaf lifespan, with larger values reflecting higher metabolic efficiency and hence less of a tradeoff. We tested how IMS evolves among closely related yet ecologically diverse milkweed species, and subsequently addressed phenotypic plasticity in response to water availability in species with divergent IMS. Integrated metabolic strategy varied strongly among 20 Asclepias species when grown under controlled conditions, and phylogenetic analyses demonstrate species‐specific tradeoffs between carbon gain and water loss. Larger IMS values were associated with species from dry habitats, with larger carboxylation capacity, smaller stomatal conductance and smaller leaves; smaller IMS was associated with wet habitats, smaller carboxylation capacity, larger stomatal conductance and larger leaves. The evolution of IMS was dominated by changes in species’ demand for carbon (δ13C) more so than water conservation (Δ18O). Although some individual physiological traits showed phylogenetic signal, IMS did not. In response to experimental decreases in soil moisture, three species maintained similar IMS across levels of water availability because of proportional increases in δ13C and Δ18O (or little change in either), while one species increased IMS due to disproportional changes in δ13C relative to Δ18O. Synthesis. IMS is a broadly applicable mechanistic tool; IMS variation among and within species may shed light on unresolved questions relating to the evolution and ecology of plant ecophysiological strategies.