Annals of botany最新文献

Background and aims: Plant dehydration and rehydration cycles are universal phenomena in natural environments, especially in arid environments. Once a moderate water stress is relieved, the plant hydraulic system can recover, but the recovery process across roots, stems and leaves remains unknown. We examined the recovery dynamics of plant hydraulics and photosynthetic activity following moderate water stress in one herbaceous plant (Glycine max) and one woody shrub (Caragana korshinskii).

Methods: The research was conducted on pot-grown plants in a glasshouse and the recovery dynamics of the predawn leaf water potential (ψleaf), hydraulic conductance of the leaf (Kleaf), of stem (Kstem) and of root (Kroot), stomatal conductance (gs), leaf photosynthetic rate (An) and nonstructural carbohydrates (NSC) were monitored after the plants were released from a moderate water stress.

Key results: Under moderate water stress with decreasing predawn ψleaf, Kleaf and Kroot in both species were more sensitive to water deficit than was Kstem, and the decrease in gs was faster than that in An, resulting in an increase in water use efficiency (WUEi); NSC decreased in leaves and stems but accumulated in roots. After rehydration, both species showed a faster recovery in Kroot and Kstem than in Kleaf, and a slower recovery in gs than in An, resulting in an increase in WUEi.

Conclusions: The rapid recovery in Kroot contributes to plant recovery from water stress, and slow recovery in Kleaf limits stomatal reopening, thus reducing transpiration and maintaining high WUEi. These traits enable species to tolerate drought.

Background and aims: A quarter of the assessed carnivorous plants (CPs) are threatened with extinction, and the effectiveness of ex situ conservation initiatives must be evaluated to complement in situ conservation efforts. Conventional seed storage (e.g., 15% relative humidity, -20°C) is the most common and efficient strategy for plant ex situ conservation, but seeds of diverse CPs might be short-lived at these conditions. Thus, there is a need to empirically and comparatively assess their longevity and evaluate the success of alternative storage options.

Methods: Diverse seed collections were used to assess longevity of seeds of thirteen CP species stored (some up to 30 years) at various storage conditions: ambient/uncontrolled, conventional, and cryogenic.

Key results: The relative short longevity of CP seeds stored in ambient/uncontrolled and conventional conditions was confirmed for some taxa (e.g., Drosera rotundifolia L.). Nevertheless, despite this potential short longevity, seeds of 64% of accessions tested retained their initial viability for up to two decades when stored at conventional seed bank conditions. Only some accessions stored for longer times (> 25 years), showed significant signs of deterioration, with D. rotundifolia and D. anglica Huds. showing P50 values in the region of other taxa considered medium/short or short-lived at comparable cold/dry storage conditions. As an alternative (or complement) to conventional seed banking, cryogenic storage of dry seeds was able to preserve a high germination percentage of seeds of CPs stored up to two decades. Furthermore, seedlings obtained developed normally into healthy plants when monitored up to 1.5 years after germination.

Conclusions: Despite the potential short lifespan of seeds of some CP taxa, this paper highlights and supports their routine dry storage in ex situ conservation programs to support in situ conservation initiatives.

Background and aims: Climate change, particularly the increased frequency of extreme climatic events, poses significant challenges to the biodiversity and functionality of semi-natural grasslands. However, the response of plant functional traits of grassland communities to climate extremes is still an unresolved issue. Using data from a long-term experiment, we aimed to characterize the functional response of a grassland community to simultaneous long-term effects of grazing and climate extremes.

Methods: For over a 20-year period, we monitored the species composition of grazed and ungrazed grassland plots. We measured functional traits defining the Leaf Economics Spectrum (LES) and the Hydraulic Safety-Efficiency (HSE) trade-offs, and we identified the temporal dynamics of single traits at the community level as well as the changes in functional strategies among grazed and ungrazed communities. Then, we assessed the role of climatic extremes in driving the changes in functional composition.

Key results: Grazed plots, in the first few years, were dominated by fast-growing species with more acquisitive strategies compared to ungrazed plots. However, both communities showed a reorganization in the functional structure over time, pointing towards a selection of trait combinations favoring more conservative, stress-tolerant strategies. The joint effect of grazing and climate extremes significantly altered the functional composition of the grazed community, leading to a shift from species with grazing-tolerant traits to species with grazing-avoidant, and drought-tolerant, traits.

Conclusions: We found that grazing pressure generally promoted functional diversity but led to rapid shifts in community composition when combined with prolonged drought events. In contrast, the ungrazed community, dominated by species with conservative resource-use strategies, showed more stable functional richness and divergence, as well as a reduced sensitivity to climatic extremes. These results underscore the importance of carefully evaluating grazing in the context of climate change, particularly to guide restoration and conservation efforts.

Background and aims: Rapid global biodiversity loss emphasizes the need to employ strategies that conserve the long-term viability of ex situ plant collections. A pedigree-based management approach is an effective strategy to track genetic diversity of living collections; however, its implementation requires accession-level data for all individuals across all botanic garden collections. Here, we use historic accession records to construct a pedigree and test how effective current protocols have been in managing ex situ diversity.

Methods: We selected the titan arum, Amorphophallus titanum (Araceae), for this study, as it is exceptional, endangered, and has been globally held in collections for nearly 150 years. A pedigree-based data management approach would benefit the ex situ conservation of many similar species. Using accession data from nearly 1200 individual plants from 111 institutions worldwide, we constructed a pedigree to track the history of this species in collections and evaluate how well genetic diversity has been maintained in the metacollection.

Key results: We found that data and records for the ex situ metacollection of Amorphophallus titanum are severely lacking and are not standardized within the botanical community. Using the available data, we found that the metacollection is derived from few founders, material is rarely exchanged between institutions on different continents, and nearly a quarter of known crosses are between related individuals.

Conclusions: Our work highlights the need for consistent, detailed record-keeping for effective implementation of an informed pedigree-based management approach and long-term maintenance of collections of endangered plant species in botanic gardens.

Background and aims: Fungal associations with photosynthetic microbes have regularly been invoked as precursors to the evolution of land plants and their mycorrhizal associations. The fungus Geosiphon pyriformis (Glomeromycotina) deviates from its arbuscular mycorrhizal (AM)-forming relatives through the presence of an intracellular symbiosis with Nostoc cyanobacteria, and is frequently viewed as the only extant representative of an ancient and formerly widespread association between fungi and cyanobacteria that occupied early terrestrial ecosystems. Here we add to growing evidence suggesting the Geosiphon-Nostoc-like associations are not ancestral to AM associations and did not occupy landscapes prior to the evolution of land plants. In addition, we discuss the underlying drivers contributing to the origination and persistence of this argument and discuss other ways in which Geosiphon has been misunderstood.

Methods: We inferred timescaled phylogenies of Glomeromycotina and utilized ancestral state reconstruction to both evaluate the plausibility of a Geosiphon-like ancestral state, and highlight the additional complexity required to maintain support for a Geosiphon-like ancestral state.

Key results: Our analyses overwhelmingly recovered the Geosiphon-like state as being derived from AM associations.

Conclusions: Our work illustrates the diverse ways in which Geosiphon has been misunderstood and adds to a growing body of evidence suggesting the Geosiphon-like ecology is derived from AM-forming ancestors and did not occupy terrestrial ecosystems prior to the evolution of land plants. We conclude by discussing outstanding questions pertaining to the ecology and evolution of Glomeromycotina fungi.

Background and aims: The Brassicaceae and many species of its various genera are currently recognized as models in various fields of biology. The impact of the major advancements in molecular phylogeny, development, genomics, and related fields on the systematics of the family led to the recognition of the first phylogenetic tribal classification of the family and recognition of monophyletic genera. The present review is aimed to cover almost all advancements in the family systematics for the first time.

Methods: The comprehensive literature on the molecular phylogeny, development, cytology, genomics, and related fields was assembled relative to its systematics value to Brassicaceae, especially for tribal classification, generic delimitation, origin, hybridization, and migration.

Key results: Adjustments to the limits of problematic tribes Brassiceae, Coluteocarpeae, and Thelypodieae, as well as various genera (e.g., Atacama, Delpinophyton, Menonvillea, Noccaea, Pseudoarabidopsis) are discussed and likely solutions are suggested. A complete list of apomorphic characters in the family is assembled for the first time, and all species or genera in which they occur are listed.

Conclusions: The current comprehensive review is the first historical advancement of the Brassicaceae systematics during the past three decades, and it aimed to help current and future students of the family to understand the background of such developments.

Background and aims: Like numerous patterns in ecology and evolution, the Latitudinal Diversity Gradient (LDG) varies across phylogenetic levels. Yet, studies that systematically investigate how patterns and processes change at different phylogenetic levels, from the tips to the root, are still relatively scarce. Here, we test the hypothesis that, despite the high long-distance dispersal capacities of liverworts, which would expectedly result in the homogenization of their distributions, an increase of diversity with latitude persists at increasing phylogenetic level due to macroclimatic niche conservatism since the earliest evolutionary history of the group.

Methods: Liverwort distributions were scored for 450 operational geographic units (OGU) world-wide. From the tips to the root, the phylogeny was continuously sliced to examine how taxonomic and phylogenetic diversity correlate with latitude in a standardized way. Taxonomic diversity and Mean Phylogenetic Distance among taxa were computed for each OGU at different phylogenetic levels and correlated with macro-ecological factors using spatial linear models.

Key results: The correlation between taxonomic diversity and latitude progressively shifted from significantly negative at species level to unsignificant and then significantly positive at the highest phylogenetic levels. Taxonomic diversity and MPD were both significantly correlated with macro-climatic factors across all phylogenetic levels.

Conclusions: In contrast with the marked increase of angiosperm family diversity towards the tropics, the latitudinal diversity gradient evidenced at species level in liverworts progressively decayed at increasing phylogenetic level, suggesting that phylogenetic niche conservatism has played a much weaker role in liverworts than in angiosperms. The inverted latitudinal diversity gradient towards the deepest phylogenetic levels lends support to the hypothesis that the earliest lineages diversified in extra-tropical conditions, explaining why, unlike in angiosperms, high species richness in the tropics is not associated with high phylogenetic diversity in liverworts. Our results highlight the extent to which a phylogenetically deconstructive approach allows for a better understanding of the accumulation of biodiversity through time.

Background and aims: Climate change is altering biodiversity by shifting species' ranges. Yet, the mechanisms underlying these shifts are not well understood for plants, whose responses to changes in precipitation or temperature are often idiosyncratic. Here, we evaluated if ecological strategies mediate tree growth and whether intraspecific trait diversity shifts across the range of an endemic tree species in a region experiencing a extreme drought.

Methods: We measured functional traits of 45 individuals of Kageneckia angustifolia from populations at the center and trailing and leading edges of its distribution, i.e. where abiotic stress is higher and lower, respectively, in central Chile. We identified individual-level ecological strategies using leaf and xylem traits and tested their association with tree growth, and estimated statistical moments of intraspecific trait variation and multidimensional trait diversity across populations with bootstrapping.

Key results: We found that intraspecific trait variation of K. angustifolia was dominated by three ecological strategies: hydraulic safety and efficiency, resource use, and water use. Across populations, tree growth was positively correlated with the hydraulic safety and efficiency ecological strategy, xylem traits, and leaf thickness. Our results show that mean leaf traits shifted towards values associated with conservative resource use and xylem traits shifted towards values associated with hydraulic safety in the trailing edge. Similarly, variance decreased towards the trailing edge, skewness was positive for most traits, and kurtosis was largely negative. Consequently, multidimensional trait diversity decreased non-linearly towards the trailing edge.

Conclusions: Our results revealed that asymmetric environmental filtering shifted trait distributions and, therefore, lowered trait diversity of K. angustifolia, likely due to increasing drought stress. Our results suggest that these shifts enable greater persistence of populations at the trailing edge, yet the species' long-term viability likely depends on its capacity to disperse to sites with suitable abiotic conditions beyond its current distribution.

Background and aims: Dynamic global vegetation models (DGVMs) are essential for quantifying the role of terrestrial ecosystems in the Earth's climate system, but struggle with uncertainty and complexity. Eco-evolutionary optimality (EEO) theory provides a promising approach to improve DGVMs based on the premise that leaf carbon gain is optimized with resource costs. However, the timescales at which plant traits can adjust to environmental changes are not yet systematically incorporated in EEO-based models. Our aims were to identify temporal constraints on key leaf photosynthetic and leaf functional traits, and develop a conceptual framework for incorporation of temporal leaf trait dynamics in EEO-based models.

Methods: We reviewed scientific literature on temporal responses of leaf traits associated with stomata and hydraulics, photosynthetic biochemistry, and morphology and lifespan. Subsequent response times were categorized from fast to slow considering physiological, phenotypical (acclimation), and evolutionary (adaptation) mechanisms. We constructed a conceptual framework including several key leaf traits identified from the literature review. We considered temporal separation of dynamics in the leaf interior to atmospheric CO2 concentration (ci:ca) from the optimal ci:ca ratio χ(optimal), and dynamics in stomatal conductance within the constraint of the anatomical maximum stomatal conductance (gsmax). A proof-of-concept was provided by modelling temporally-separated responses in these trait combinations to CO2 and humidity.

Key results: We identified 15 leaf traits crucial for EEO-based modelling and determined their response mechanisms and timescales. Physiological and phenotypical response mechanisms were considered most relevant for modelling EEO-based trait dynamics, while evolutionary constraints limit response ranges. Our conceptual framework demonstrated an approach to separate near-instantaneous physiological responses in ci:ca from week-scale phenotypic responses in χ(optimal), and to separate minute-scale physiological responses in stomatal conductance from annual-scale phenotypic responses in gsmax.

Conclusions: We highlight an opportunity to constrain leaf trait dynamics in EEO-based models based on physiological, phenotypical and evolutionary response mechanisms.

Background and aims: the complex thalloid liverworts (Marchantiales) are an iconic group of bryophytes that have been long speculated to be one of the oldest lineages of land plants. Even though a thorough review of their fossil record has recently enhanced our understanding of their evolutionary history, few fossils have been found to preserve fertile characters. Here, we describe a new fertile marchantioid fossil from the Late Triassic of Argentina and assess its phylogenetic affinities.

Methods: the new fossil was scored into an extensive morphological matrix encompassing both extant and fossil bryophytes. To thoroughly assess the position of the fossil, phylogenetic analyses applied two taxon samplings: a broad sampling of bryophytes and a focal sampling of Marchantiales. Topologies were inferred under equal weighting and extended implied weighting, including character dependencies as step-matrices complexes. The optimal topologies inferred under equal weighting were finally time-calibrated using the First Appearance Data (FAD) for species.

Key results: our analyses indicate a clear affinity of the new fossil with the xerophytic Marchantiales, although its precise placement within the order depends on the analytical approach. Time-calibrating the optimal topologies led to xerophytic lineages diverging in the interval Late Permian-Early Triassic, which is older than previously inferred. The inclusion of the new fertile fossil implies that specialised branches were undergoing reduction already by the Early Mesozoic.

Conclusions: through the description and analyses of a new Early Mesozoic fossil, our study reveals a novel trend in the evolution of specialised fertile branches in Marchantiales. Likewise, according to our time-calibrating, the radiation of xerophytic lineages is inferred older than in previous studies. Our study highlights the importance of discovering new fossils to close the gap in our knowledge of the evolutionary history of the complex thalloid liverworts.