Annals of botany最新文献

Background and aims: It is assumed that trees should adapt their above and belowground organs as they age. However, most studies to date have quantified these trait adjustments in homogeneous forest stands, confounding the effect of stand aging on soil properties and the intrinsic response of trees to aging.

Methods: Here, we examined 11 morphological, architectural, anatomical and mycorrhizal fine root traits of each of the first five orders for 66 Pinus koraiensis individuals of 16 to 285 years old in northeast China, while accounting for soil characteristics (pH and total C, N and P concentrations).

Key results: Across all absorptive root orders, Hartig net area and mantle thickness, representative of P. koraiensis reliance on ectomycorrhizal association, displayed an orthogonal pattern to traits describing root economics strategy, specific root length and root tissue density. Hartig net area and mantle thickness were not significantly related to root mycorrhizal colonization intensity and root branching intensity. As tree aged, there was a trade-off between increasing specific root length and decreasing root tissue density in all root orders we measured. Trees facing soil conditions with lower N or P concentrations showed higher dependence on ectomycorrhizal fungi.

Conclusions: This work provides evidence that tree belowground economics strategy can change significantly along the life of trees. In the ectomycorrhizal tree species studied, morphological adjustments are most pronounced, whereas mycorrhizal strategy remains largely consistent. The more conservative root strategy of younger trees than older ones contradicts previous results on the aging of homogeneous tree stands, suggesting that individual tree responses to aging in mixed-aged forests may strongly differ from those in homogeneous forest stands experiencing multiple confounding environmental influences.

Background and aims: Understanding interspecific differences in plant growth rates and their internal and external drivers is key to predicting species responses to ongoing environmental changes. Annual growth rates vary among plants based on their ecological preferences, growth forms, ecophysiological adaptations, and evolutionary history. However, the relative importance of these factors remains unclear, particularly in high-mountain ecosystems experiencing rapid changes.

Methods: We examined how habitat associations, elevational optima, growth forms, and ecophysiological and anatomical traits influence interspecific differences in radial growth rates among 324 vascular dicot species naturally occurring in the western Himalayas. Growth rates were determined from annual ring width measurements on the oldest plant sections of over 7,800 individuals from a range of habitats (desert, steppe, wetland, alpine, subnival), growth forms (perennial tap-rooted, rhizomatous, cushiony, woody), and climatic gradients (elevations of 2,650-6,150 m).

Key results: Habitat associations accounted for 24% of the variability in interspecific growth rates. Adding growth form and height increased the explanation to 42%, and incorporating plant functional traits further improved predictions to 46%. Growth rates were higher in warmer, drier conditions and lower in cold, wet environments. Subnival cushion plants had the slowest growth, while ruderal plants grew the fastest. Desert plants showed higher growth rates, reflecting their drought adaptive strategies, while wetland forbs had lower growth rates due to increased resource competition. Growth was positively correlated with leaf nitrogen content and non-structural carbohydrates (mainly fructans), due to enhanced photosynthesis and stress tolerance, and negatively correlated with leaf carbon and root nitrogen content.

Conclusion: Our study of 324 dicot species in the western Himalayas suggests that plant growth in high elevations is determined by a combination of habitat conditions, morphological traits, and ecophysiological adaptations. Growth variations among the highest-growing angiosperms reflect adaptive strategies along the global 'fast-slow' and 'acquisitive-conservative' spectrums. These results underscore the importance of habitat-specific studies for predicting plant growth responses to environmental changes, emphasizing a species-specific approach for effective conservation in fragile ecosystems.

Background and aims: Genome size varies by orders of magnitude across land plants, and the factors driving evolutionary increases and decreases in genome size vary across lineages. Bryophytes have the smallest genomes relative to other land plants and there is growing evidence for frequent whole genome duplication (WGD) across the lineage. However, the broad patterns of genome size, chromosome number, and WGD have yet to be characterized across bryophytes in a phylogenetic context.

Methods: In the present study, we use a phylogenetic comparative approach and leverage previously published data on genome size, chromosome number, and WGD to reconstruct the evolutionary history of these traits across the three major bryophyte lineages: hornworts, liverworts, and mosses. We infer ancestral haploid chromosome numbers for each lineage and introduce a novel metric for assessing polyploidy using chromosome counts.

Key results: Each lineage of bryophytes exhibits a distinct pattern of genome size evolution and prevalence of WGD, with mosses having the most dynamic genome sizes and highest propensity for WGD. We found that 21.3% of mosses and 13% of liverworts species have naturally occurring polyploids. In addition, haploid genome size (1C) is most dynamic in the mosses which includes 15 transitions to larger genomes and nine reversals, largely in the orders Dicranales and Hypnales.

Conclusions: There is no correlation between genome size and WGD or genome size and chromosome number, potentially suggesting rapid genome downsizing following WGD. As bryophytes are poikilohydric (desiccation tolerant) plants, having large genomes may be physiologically prohibitive given the cost to growth and metabolism associated with them. These findings emphasize the unique evolution of the bryophytes broadly and of the hornworts, liverworts, and mosses individually, and should therefore serve as impetus for more in-depth experimental studies of genome size evolution and WGD in bryophytes.

The biomechanical, morphological and ecophysiological properties of plant seed/fruit structures are adaptations that support survival in unpredictable environments. High phenotypic variability of noxious and invasive weed species such as Raphanus raphanistrum (wild radish) allow diversification into new environmental niches. Dry indehiscent fruits (thick and lignified pericarp [fruit coat] enclosing seeds) have evolved many times independently. Here, we demonstrate that the hard pericarp of Raphanus species (Brassicaceae) imposes mechanical dormancy by preventing full phase-II water uptake of the enclosed seeds. A multiscale biomechanics and imaging (microscopy, X-ray, finite element stress simulation, puncture force analysis) approach was used to comparatively investigate the indehiscent fruits of R. raphanistrum (global weed), R. pugioniformis (endemic weed) and R. sativus (cultivated radish). This demonstrated that the apparently unilocular fruits of Raphanus species develop from two fused valves, that pericarp rupture to permit germination is confined to the midvalve regions (MVR), and that each MVR contains a predeterimed breaking zone which is biomechanically defined by the internal shape of the seed chambers. Direct biomechanical analysis revealed great variability in within-fruit and between-fruits pericarp resistences. We conclude that variability in pericarp-imposed dormancy provides a bet-hedging strategy to affect soil seed bank persistence and prolong the germinability period.

Background and aims: Torminalis glaberrima (Gand.) Sennikov & Kurtto is a European tree species currently underutilized in forestry, valued for its high-quality wood and contribution to ecosystem stability. Despite a projected range expansion as climate change progresses, current population fragmentation levels may inhibit the species' ability to migrate and stabilize fragile forest ecosystems. To investigate the relationship between structural and functional connectivity, we surveyed the genetic diversity, spatial genetic structure, and gene flow of T. glaberrima across Austria, to understand which populations should be given conservation priority.

Methods: Our sampling encompasses 21 natural and planted populations and 910 individuals of T. glaberrima covering the species' distribution in Austria. We estimated genetic diversity indices, the extent of gene dispersal, and conducted SPAGeDi, STRUCTURE, and discriminant analyses of principal components analyses using one chloroplast minisatellite and eight nuclear microsatellite markers.

Key results: Despite a highly fragmented distribution of T. glaberrima in the southern, western and central part of its range in Austria, we found high genetic diversity, low population differentiation and inbreeding, and estimated higher gene dispersal values than previous studies. Population structure analyses identified two main regions of genetic ancestry in the northwestern and southeastern part of the species' range in Austria and evidence for the usage of foreign genetic material in two planted populations.

Conclusions: Only two of the established ex situ plantations and seed orchards appear to well represent the fine-scale population structure present in Austria, and existing in situ gene conservation units (GCUs) are insufficient to conserve the current natural genetic diversity. We suggest the establishment of further in situ GCUs to maximize the conservation of extant forest genetic diversity. Additionally, we encourage corridor plantings between isolated populations, bolstering the genetic connectivity and diversity of populations.

Background and aims: Competition with sympatric diploid progenitor(s) hinders the persistence of polyploids. The hypothesis that polyploids escape from competition through niche shifts has been widely tested; however, niche escape is unlikely to completely avoid competition. Given species growing in less favorable environments likely have weaker competitive abilities, we hypothesize that polyploid populations tend to persist in areas where their progenitors with relatively low habitat suitability.

Methods: This study investigated two sibling allopolyploid species, Achillea alpina and A. wilsoniana of the daisy family, which originated independently from the same two parental species. We explored the patterns of niche shifts between the polyploids and their progenitors by using several ecoinformatics analyses in the environmental and geographic spaces, and performed ecological niche modeling to estimate the historical distribution of these species as well as the potential regions for persistence of allopolyploids.

Key results: The niche shift patterns of the two polyploids were not completely consistent: A. alpina showed niche expansion, while A. wilsoniana exhibited a trend towards niche novelty. Their potential suitable areas were both more likely to overlap with regions where the habitat suitability values of their parental species became low.

Conclusions: The present results support our hypothesis that polyploids tend to persist their populations in areas that are less suitable for their diploid progenitors. Meanwhile, niche shifts may promote the success of polyploids. These findings contribute to our understanding of the ecological processes involved in the maintenance and persistence of polyploids.

Background: Sweet orange is an important economic crop, and salt stress can inhibit its growth and development.

Methods: In this study, we identified AP2/ERF genes in sweet orange via bioinformatics and performed a combined transcription‒metabolism analysis, which revealed for the first time the integrated molecular mechanism of salt stress regulation in sweet orange.

Key results: A total of 131 sweet orange AP2/ERF genes were identified and categorized into five groups. By comparing the tertiary protein structures of these genes with those of Arabidopsis, we found that five sweet orange genes (CsERF38, CsERF41, CsERF42, CsERF84, and CsERF110) related to salt stress and ethylene transcription are highly similar in composition and structure to those of Arabidopsis, and we hypothesize that they have similar functions. ABREs and AREs were the predominant cis-acting elements in the sweet orange AP2/ERF gene family, and both were associated with salt stress. The AP2/ERF gene family was verified to be involved in the salt stress response via qRT-PCR. According to the differentially abundant metabolite KEGG network, we chose the differentially abundant metabolites ET, GA, and JA as the primary research objects; the CsAP2/ERF gene family is an ethylene-responsive element binding factor.

Conclusion: In this study, the complete framework of the AP2/ERF gene family was constructed for the first time. A model of salt stress regulation in sweet oranges was established.

Background and aims: The currently recognized diversity of pollination strategies requires pollination syndromes to be updated. Described a decade ago, kleptomyiophily is a deceptive pollination system in which plants exploit the nutrient-seeking behavior of females of kleptoparasitic flies (Chloropidae and Milichiidae) by olfactorily mimicking their insect host. Such a pollination system was already hypothesized for pollination by biting midges (Ceratopogonidae) but has never been formalized. This review aims to explore the extent of pollination interactions deceiving anautogenous flies, especially by considering pollination by biting midges and kleptomyiophily as two facets of a common pollination syndrome: insect-host mimicry. As attraction of these flies seems to rely on insect-mimicking volatile organic compounds (VOCs), we propose an overview of the floral odours emitted by these plant species.

Methods: We compiled bibliographic data on plant species pollinated by Chloropidae, Ceratopogonidae and Milichiidae, to list plant species that could be involved in insect-host mimicry pollination strategies. Then, we reanalyzed data from the literature on floral VOCs of 18 of these plant species distributed among four plant families and compared them with related plant species performing brood-site mimicry, the pollination syndrome closest to insect-host mimicry.

Results: We show that at least 97 plant species from seven families are mainly pollinated by Chloropidae, Ceratopogonidae and Milichiidae, with almost exclusively females found in flowers. Deception of anautogenous flies has been shown for only four plant species but has been supposed for a total of 28 others. Comparison of floral VOCs shows significant differences between insect-host mimicry and brood-site mimicry in terms of chemical composition, diversity and models mimicked.

Conclusions: Despite fragmentary knowledge about the biology of the Diptera involved in insect-host mimicry, our results show similarities in floral odours and the putative mimicked resource between kleptomyiophilous plants and those pollinated by biting-midges, emphasizing a broader, unique, pollination syndrome.

Background: Plants often shift their phenology in response to climate warming, with potentially important ecological consequences. Relative differences in the abilities of native and nonnative plants to track warming temperatures by adjusting their phenologies could have cascading consequences for ecosystems. Our general understanding of nonnative species leads us to believe these species may be more phenologically sensitive than native species, but evidence for this has been mixed, likely due, in part, to the myriad of diverse ecological contexts in which nonnatives have been studied.

Scope: Here, we review the current state of knowledge on nonnative plant phenological responses to climate warming. From observational and experimental studies, we synthesize: 1) the ways in which nonnative plant phenology shifts with increased temperature, 2) the relative differences between natives and nonnatives in phenological timing and sensitivity to warming, 3) the contingencies driving variable nonnative phenological responses to warming, and 4) the ecological consequences of warming-induced phenological shifts in nonnatives.

Conclusions: Early-season phenophases tend to advance with warming, sometimes (but not always) more so in nonnative species relative to native species. Late-season phenophases, on the other hand, tend to be more variable; advancing, delaying, or remaining unchanged. Similarly, relative differences in phenological sensitivity between native and nonnative plants were less consistent for late-season phenophases. However, our ability for inference is limited by the scope of studies done to date, which best represent temperate ecosystems in the Northern Hemisphere. We found phenological shifts in nonnative species to be driven by various factors including their evolutionary histories and the environmental context of the invaded system. Shifts in nonnative phenologies result in varied ecological consequences, from shifting demographics of the nonnative species themselves, to changes in ecosystem level processes such as carbon cycling. Additional study addressing key gaps is vital to improving understanding of nonnative phenological responses to warming.

Background and aims: Kalanchoe is a diverse genus in the Crassulaceae, with centres of diversity in Madagascar and sub-Saharan Africa. The genus is known for its popularity in horticulture, its use as a model system for research on CAM photosynthesis and vegetative reproduction, its high invasive potential, and its use in traditional medicine. The genus-rank circumscription and infrageneric classification of Kalanchoe have been the subject of debate for centuries, especially regarding the status and rank of what is now treated as K. subg. Bryophyllum and K. subg. Kitchingia. We aim to generate a densely sampled phylogeny of Kalanchoe s.l. and evaluate the current infrageneric classification system.

Methods: We inferred a phylogenetic tree for Kalanchoe using a ddRAD sequencing approach, covering 70% of taxa and four out of five subgenera currently recognised in the genus.

Key results: We recovered four well-supported clades, partially corresponding to the current subgeneric classification. Kalanchoe subg. Calophygia resolves as sister to the rest of the genus. The relationships among the three remaining clades, however, receive less support. The predominantly mainland African K. subg. Kalanchoe forms a strongly supported clade that resolves as sister to K. subg. Bryophyllum. These two clades are together sister to a clade containing mainly species from K. subg. Kitchingia and K. sect. Pubescentes.

Conclusions: The current subgeneric classification of Kalanchoe is partially backed up by our phylogenetic tree but requires further refinement. The tree topology suggests a Malagasy origin of the genus and one dispersal event to the African mainland, with subsequent dispersal from continental Africa to the Arabian Peninsula and Southeast Asia. The formation of bulbils on the leaf margin is restricted to a larger clade within K. subg. Bryophyllum and thus only evolved once. Our tree provides a framework for further taxonomic, evolutionary, and physiological research on the genus.