Annals of botany最新文献

Background and aims: This study explores the genetic diversity and past range dynamics of silver fir (Abies alba) with the objective of delineating the past demography of the species, the main postglacial colonization pathways, and the current vulnerability of past glacial refuges.

Methods: We applied restriction site-associated DNA sequencing (RAD-seq) to 26 A. alba populations to explore their phylogeographic structure and historical demographic changes.

Key results: Three lineages were identified. One comprised populations from the southern range, whereas northern populations formed two lineages with subtle genetic differentiation between western and eastern populations. Northern Balkan and northeastern Apennine samples clustered within introgression zones at the intersection of postglacial recolonization routes, consistent with their intermediate geographic positions. Demographic analyses indicated that southern populations remained relatively stable as glacial refugia, whereas northern populations experienced population declines during the middle Pleistocene associated with glaciations. Although the demographic events that shaped the current spatial structure of genetic diversity of silver fir go back to the Pleistocene, human pressure during the Holocene likely led to an abrupt range decline.

Conclusions: We present a timely and broadly applicable framework for delineating the phylogeographic lineages of silver fir, leveraging the high resolution provided by SNP markers to identify major genetic discontinuities, contact zones, and refugial areas. Inferences of past demographic dynamics indicate that certain rear-edge populations warrant priority in conservation strategies.

Background and aims: Plant survival at extreme elevations depends on how carbon and nutrients are stored and mobilized at the cellular scale. High-elevation plants experiencing persistent cold and short growing seasons are predicted to maintain large pools of non-structural carbohydrates (NSCs) and extensive storage tissue that buffer metabolism and enhance stress tolerance, yet comparative evidence across diverse floras remains scarce. Here, we examine whether high-mountain plants in the western Himalayas increase NSC pools and, consequently, the proportion of storage tissue.

Methods: We analyzed 323 herbaceous species from the western Himalayas spanning 2,650 to 6,150 meters. For each species, storage organs were examined anatomically and chemically. Belowground tissues were sectioned to quantify parenchyma and lignified fractions, and the same organs were analyzed for soluble sugars, fructans, starch, nitrogen, and phosphorus. Relationships between elevation, tissue anatomy, plant height, and biochemical composition were evaluated using phylogenetically informed models.

Key results: Elevation increased NSC and nutrient concentrations, and these storage pools were linked to the expansion of parenchymatic tissue at the expense of lignified mechanical tissue. Plant height declined with elevation but showed no consistent relationship with anatomy, excluding a passive dwarfism explanation of increased parenchyma fraction. Among NSC classes, osmotically active soluble sugars and fructans, but not starch, were strong predictors of parenchyma abundance and also tracked elevation.

Conclusions: These coordinated anatomical and physiological shifts indicate a physiology-to-anatomy linkage in which elevation-related accumulation of mobile reserves and nutrients expands living storage cells, enhances cryoprotection by lowering cellular osmotic potential, limits ice propagation, and buffers metabolism against intermittent carbon and nutrient acquisition. By connecting cellular storage pools to tissue architecture across more than three hundred Himalayan species, this study reveals a widespread yet underexplored mechanism of alpine adaptation and provides a framework for understanding how storage physiology shapes plant persistence in cold, resource-limited ecosystems.

Background and aims: Old-growth subtropical grasslands are often underestimated in their capacity to store carbon. Growing recognition of belowground plant biomass as an important measure of ecosystem health and organic carbon storage potential has led to the application of allometric equations to predict root biomass from aboveground biomass measurements, commonly expressed as a root-to-shoot ratio (RSR). Furthermore, the carbon storage potential of ecosystems is often estimated using a standard carbon conversion factor (CCF), typically set to 0.45 x dry biomass. However, studies validating these estimates for their application in grasslands are mostly from temperate and alpine ecosystems, making RSR- and subsequent CCF-based carbon estimates unreliable in subtropical grasslands.

Methods: Biomass sampling was conducted at two subtropical grassland sites in South Africa representing contrasting rainfall regions (semi-arid vs. moist grasslands). Root and shoot biomass were destructively harvested to calculate site-specific RSRs. Elemental organic carbon content was measured and compared with the 0.45 CCF used in global carbon estimation approaches.

Results: The mean RSR across our study for subtropical grasslands was 14.9, approximately five times higher than the global average of 3.22. RSR varied with rainfall, with 19.7 in moist grasslands and 8.9 in semi-arid grasslands. The default CCF of 0.45 overestimated carbon content in both above- and belowground biomass, with a proposed adjusted CCF of 0.39 reflecting a more accurate estimate. However, when both RSR and the adjusted CCF are applied, subtropical grasslands store 10 tC ha-1 more carbon than would be predicted using global defaults.

Conclusions: Applying global conversion factors without accounting for regional variability leads to inaccurate carbon stock estimates, particularly in subtropical grassland systems where belowground allocation dominates. Accurate RSRs and CCFs are therefore critical for accurate carbon modelling and promoting conservation in these underrepresented ecosystems.

Background and aims: As the stigma of female flower in maize, silks emerge sequentially from ear base to apex, potentially causing barren ear tip. This study aimed to reveal the underlying regulatory mechanisms in coordinating the elongation of a cohort of silks on an ear.

Methods: Morphological, physiological, metabolic and transcriptional investigations were performed on silks from basal, middle and apical regions of an ear at the initial (T1), rapid elongation (T2), and silking stages (T3), respectively.

Key results: Silk extension rate and length progressively declined from ear base to apex, correlated with decreased hexose availability due to lower sucrose supply and weaker sucrose decomposition, as well as the gradient phytohormone deposition. Further comparative analyses on silk metabolomics and transcriptomics between three stages and three positions identified the stage-specific and position-specific genes and metabolites. The elongation of silks at three positions involves the common pathways including sugar and amino acid depletion, secondary metabolite biosynthesis, and phytohormone responses. Stage-specific pathways indicated that nucleic acid metabolism was predominant at T1, carbohydrate and energy metabolism at T2, and defense metabolism at T3. Position-specific pathways highlighted the earlier biosynthesis of secondary metabolites in basal silks, and delayed phytohormone signaling, starch and sucrose metabolism, and mitogen-activated protein kinase (MAPK) signaling in apical silks. At T3, silk senescence progressed from ear base to apex by having more severe sugar depletion, salicylic/jasmonic acids deposition, and active brassinosteroid/abscisic acid synthesis.

Conclusions: The sequential silk elongation on an ear is collectively coordinated by assimilates competition, phytohormone signals, and secondary metabolism, providing foundations for crop improvement in combating barren ear tip.

Background and aims: Global environmental changes significantly impact nitrogen (N) and phosphorus (P) availability in desert steppes, thereby reshaping plant species interactions and ultimately influencing ecosystem structure and functioning. This study investigated how these nutrients affect the competitive interactions between legumes and grasses by altering their adaptive strategies.

Methods: Pot experiments were conducted using the dominant grass species, Stipa breviflora, and the leguminous species, Melissitus ruthenica, under different treatments involving control without nutrient inputs, N input alone, P input alone, and combined N and P inputs. Plant growth, nutrient uptake, and root traits were evaluated in monocultures and mixed plantings.

Key results: In the relatively N-enriched desert steppes, P addition increased grass biomass by 76% in monocultures; however, this effect was not observed when they were planted alongside leguminous species. Legumes exhibited a more pronounced response to P supplementation, with biomass increasing by up to 106%. The relative total biomass (RBT) remained below 1 across all treatments, indicating the presence of interspecific competition. In simultaneous mixed planting, grass species were dominant under N-only treatments, whereas legumes exhibited a competitive advantage under P-only treatment. The concentrations of N and P in shoots of grasses remained unchanged following nutrient inputs and coexisting with legumes. In contrast, the N and P concentrations in legume shoots demonstrated the contrary trends, and were negatively and positively correlated with biomass, respectively. Both grasses and legumes increased total root length and reduced root diameter when coexisting. The priority effect (i.e., first seeding) enhanced the secretion of acid phosphatase and carboxylates by roots of legumes, and coexistence stimulated those root exudates in grasses.

Conclusions: Nitrogen inputs moderately enhance grass growth, whereas P inputs benefited legumes by modifying rhizosphere processes, thereby mitigating their competitive disadvantage under N enrichment. These findings highlight the potential for global change-induced reduced P availability to shift plant dominance in grasslands.

Background and aims: Plant biomass allocation serves as a core adaptive strategy for buffering against environmental fluctuations. Optimal partitioning theory (OPT) and allometric partitioning theory (APT) provide distinct theoretical frameworks to explain the underlying resource allocation dynamics. Yet, how functional traits govern biomass allocation patterns and interspecific differences in C3 and C4 grasses under altered precipitation regimes resulting from variations in precipitation amount and frequency remains poorly understood.

Methods: A factorial pot experiment was conducted using a randomized complete design with three precipitation amounts (175, 350, 525 mm) and three precipitation frequencies (10, 20, 30 events) to investigate physiological traits and biomass allocation strategies of a C3 grass (Leymus chinensis) and a C4 grass (Hemarthria altissima).

Key results: Our results revealed: (1) H. altissima (C4) exhibited lower physiological sensitivity to precipitation variability compared to L. chinensis (C3); (2) Both the studied C3 and C4 grasses showed significant allometric relationships between aboveground (AGB) and belowground (BGB) biomass (P < 0.001), yet the root-to-shoot ratio (R/S) remained responsive to precipitation treatments even after accounting for plant size effects; (3) A principal component analysis (PCA) identified two orthogonal axes of physiological variation: the first principal component (PC1, photosynthetic growth dimension) was positively correlated with total biomass, while water use efficiency (WUE, analyzed as an independent water balance dimension) was associated with greater BGB, lower AGB, and higher R/S.

Conclusions: These findings demonstrated that biomass allocation in these grasses is co-regulated by allometric constraints and environmental plasticity, aligning with the complementary predictions of APT and OPT, and mediated by distinct physiological dimensions (i.e., PC1 driving growth and WUE governing allocation). While the C3 and C4 grasses share these regulatory mechanisms, they exhibit divergent physiological sensitivities to precipitation variability, highlighting the necessity of integrating functional trait dynamics when modeling plant responses to changing precipitation regimes.

Background and aims: Fire is a major ecological force that shapes population dynamics and community structure in terrestrial ecosystems. Understanding seed germination responses to fire cues is crucial for predicting post-fire vegetation recovery. However, under the changing global fire regime, such responses in non-fire-prone ecosystems remain largely unknown. Here, we aimed to understand how fire influences population recruitment in non-fire-prone temperate grasslands and whether this influence is associated with key regenerative traits.

Methods: We conducted a seed germination experiment with 80 species originating from a non-fire-prone temperate grassland ecosystem, using Bayesian phylogenetic mixed-effects models to examine the effects of fire cues on seed germination.

Key results: We found that smoke and heat resulted in modest yet statistically significant increases in germination percentage. Germination of 24 species was significantly promoted by fire cues, among which 11 species responded significantly to heat shock and 13 species to smoke. However, these responses showed no significant phylogenetic signal. Furthermore, dormancy types were closely associated with the specific fire cues required to release dormancy, and annual and perennial species displayed markedly different germination responses to fire cues.

Conclusions: This study investigates the critical role of fire cues in breaking seed dormancy in a non-fire-prone temperate grassland ecosystem. The differential germination responses among species are driven by dormancy type and lifespan. Although the overall increase in germination percentage was modest, the differential responses of seed germination to fire cues among species and functional groups reveal the potential importance of wildfires in reshaping community structure and composition. Our findings provide new insights into post-fire vegetation dynamics in the temperate grasslands.

Background and aims: Sphagnum imbricatum sensu lato (Sphagnum, subgenus Sphagnum) is sometimes considered a single widespread and polymorphic species, or up to four separate species. This study was conducted to provide a phylogenetic delimitation of the S. imbricatum complex, assess species delimitation within the complex, and evaluate likely parentage of five allopolyploid species in subg. Sphagnum that may be related to haploid species in the complex.

Methods: RADSeq data were assembled from 192 samples of subg. Sphagnum plus three outgroup taxa from related Sphagnum subgenera. Parentage of allopolyploids was assessed using STRUCTURE, and differentially fixed SNPs among haploid taxa and their distribution within and among the allopolyploids.

Key results: The S. imbricatum complex was circumscribed to include S. affine, S. austinii, S. imbricatum, S. portoricense, and S. steerei. The traditionally recognized species, S. affine, was resolved to include two morphologically similar clades that are phylogenetically divergent (non sister groups) within the complex. All the northern allopolyploids were derived from crosses between species in the S. imbricatum and S. magellanicum complexes.

Conclusions: The two clades formerly known as S. affine s.l. will need to be recognized as separate species pending in-progress morphological study. Our results suggest testable hypotheses about specific haploid taxa identified as likely parents of the allopolyploid species. Newly resolved phylogenetic relationships among species in the S. imbricatum complex indicate that the tropical species, S. portoricense, is nested within a clade otherwise distributed in arctic to temperate regions, empowering this group for research about warm climate adaptation utilizing naturally occurring variation.

Background and aims: Fine root anatomy directly affects drought resistance through water transport efficiency and storage capacity, while its variation may be phylogenetically constrained, reflecting evolutionary selection of drought adaptation strategies. While fine roots exhibit remarkable functional plasticity, the phylogenetic imprint on their anatomical trait variation patterns remains unclear, highlighting a critical knowledge gap in plant adaptation strategies.

Methods: This study investigated 21 local tree species from northern subtropical China to quantify anatomical traits across first- to fifth-order fine roots. By integrating drought resistance assessments with phylogenetic signal analysis (K - value), we investigated how plant species, root order, and their interactions drive functional differentiation in fine roots. Our findings elucidate adaptive strategies in absorption-transport trade-offs while delineating phylogenetic constraints on trait variation.

Key results: Our results demonstrate: (1) Species and root order jointly drive adaptive differentiation in fine root anatomy, where root diameter, cortex ratio, vessel diameter, and root cross-sectional area emerge as key drought-resistance traits; (2) PCA revealed cortex traits dominate water absorption (PC1), while vessel traits (vessel density and stele ratio) govern transport capacity (PC2); (3) Phylogenetic analyses showed strong conservatism in first- to fourth-order roots, with evolutionary history accounting for significant trait variation, underscoring phylogenetic constraints on functional adaptation. This study deciphers the dual regulatory framework of fine root anatomical adaptation to drought stress, integrating eco-physiological trait networks with phylogenetic constraint analysis.

Conclusions: These findings not only amplify the fundamental understanding of evolutionary trade-offs in plant hydraulic strategies, but also establish a mechanistic basis for precision selection of afforestation species.

Background: Leaf dark respiration (Rd) responds to short-term temperatures and acclimates to changes in long-term temperatures. Although accurate Rd-temperature (Rd-T) models are crucial for carbon flux prediction in forest ecosystems, two thermodynamically grounded frameworks-the macromolecular rate theory (MMRT) and the general temperature dependence (GTD) model-have not been compared. Moreover, these models can uniquely link molecular processes to leaf-scale Rd, providing mechanistic interpretations of thermal acclimation that empirical models cannot achieve.

Methods: Here, we grew two common subtropical species, Cyclobalanopsis glauc and Schima superba, in artificial climatic chambers under three temperature treatments (daytime/nighttime = 30/25°C, 25/20°C, and 20/15°C). After 15 days of temperature treatment, Rd-T response curves were measured at night.

Key results: Despite both models showed equivalent predictive power (R², AICc, RMSE), MMRT was prioritized for its detailed mechanistic interpretation, which links the molecular conformation to temperature-dependent leaf Rd via temperature-dependent changes in heat capacity (ΔC). Although both species employ type II thermal acclimation, the thermal acclimation strategies differ: for C. glauca, the increase in ΔC under warming suggests a shift toward enhanced enzyme conformational flexibility, achieving partial homeostasis. In contrast, S. superba exhibited overcompensation without changes in ΔC or activation enthalpy (ΔH), indicating a strategy governed by factors independent of these thermodynamic parameters.

Conclusions: In our study, the MMRT model is recommended to fit Rd-T response curves, and ΔC serves as a bridge between thermodynamic principles and species-specific thermal acclimation mechanisms, successfully distinguishing the strategy of C. glauca (associated with changing enzyme thermodynamics) from that of S. superba (independent of such thermodynamic adjustments).