Annals of botany最新文献

Background: Foliar water uptake (FWU) and its role in hydraulic redistribution are critical yet understudied mechanisms, particularly in temperate tree species of Europe.

Methods: This study investigates FWU in beech (Fagus sylvatica L.), with a focus on its contribution to the tree's water balance beyond leaf level. By using a combination of different imaging techniques such as silver nitrate tracing, positron emission tomography (PET) and autoradiography, we identified foliar water uptake from the point of entry to its subsequent transport.

Key results: The ionic tracer, silver nitrate (AgNO3), precipitated mainly at trichome bases and extended into subepidermal tissues, enabling the identification of water entry points. However, its inability to reach deeper vascular structures limited the ability to draw conclusions about further water transport and redistribution. Therefore, PET imaging and autoradiography were used and successfully visualized reverse sap flow of radiotracer-labelled water from treated leaves to connected branches, driven by a significant water potential gradient Δψ of 1.4 ± 0.9 MPa. Compartmental modelling quantified a net exchange rate eX-P of 0.15 ± 0.07 min-1 between xylem and surrounding parenchyma and a front velocity vFWU of 3.31 ± 0.56 mm min-1 under the imposed Δψ.

Conclusions: These findings demonstrate that FWU may actively contribute to replenishing branch water pools, emphasizing its role as a critical hydraulic mechanism. This research underscores the utility of integrating PET imaging with complementary methods to better understand FWU dynamics and its implications for plant water budgets under changing climatic conditions.

Background and aims: Flower petal integrity affects the success of plant reproduction and ecological adaptability. The mechanical resistance of plant organs indicates their capacity to withstand physical damage and preserve structural integrity. However, little is known about the mechanical resistance of flowers and their differences from leaves.

Methods: To address the aforementioned research gaps, we quantified flower petals from 43 species and leaves from 86 species, employing two forces that characterize mechanical resistance: force to punch and force to tear. For force to punch, three different diameter punch needles were used to measure and three methods were employed for calibration. Additionally, we measured functional traits of petals and leaves.

Key results: We found that petals have significantly lower mechanical strength than leaves in both punch and tear forces. The force to punch and force to tear of petals and leaves were positively correlated with tissue thickness, cuticle thickness and dry mass per unit area. The vein density of petals was positively correlated with force to punch and force to tear, while force to tear was negatively correlated with floral tissue density after phylogenetic independent contrast correlation analysis. For reticular venation leaf, the vein density had no significant relationship with force to tear, but was positively correlated with tissue density.

Conclusions: Our results indicated that there were differences in the structural basis of mechanical resistance between flowers and leaves. Regarding the most classical mechanical testing method, force to punch, different needle diameters and calibration methods can affect the results for both the petal and leaf. Our research results provide an important reference for better understanding the ecological adaptability of flowers.

Background: Gynandropsis gynandra (Cleomaceae; formerly Cleome gynandra) is a leafy vegetable widely cultivated across Africa, uniquely positioned at the intersection of agricultural and evo-devo research. It is gaining recognition as an 'opportunity crop', valued locally for its nutritional and medicinal properties with ongoing agricultural research aimed at the development of improved cultivars and agronomic practices. Concurrently, its close evolutionary proximity to Arabidopsis thaliana, combined with its contrasting traits, positions G. gynandra as a model for studying C4 photosynthesis and floral development. Despite its relevance to both agricultural and evo-devo research, integration of findings between disciplines remains limited, hindered in part by inconsistent nomenclature and the lack of standardized morphological descriptors.

Scope: To address this disconnect, this review synthesizes findings from agricultural and evo-devo research on G. gynandra. We provide an overview of its phylogenetic placement, geographical distribution, agricultural and medicinal applications, phytochemical profile, genomic and genetic resources, and morphological traits. In doing so, we emphasize the duality of G. gynandra as both a crop of agronomic interest and a model for evo-devo studies. Finally, we propose future research directions to promote cross-disciplinary collaboration and expedite progress in G. gynandra research.

Conclusions: Advances in molecular tools have improved our understanding of the developmental mechanisms underlying key traits and physiological adaptations in G. gynandra, including C4 photosynthesis and antiherbivore defences. Simultaneously, morphological studies have revealed distinctive floral features and substantial phenotypic diversity, offering valuable insights for both breeding initiatives and investigations into floral development. Integrating data and resources from agricultural and evo-devo research will accelerate the improvement of G. gynandra and broaden its utility as a model for understanding trait evolution and development.

Background and aims: Cycads are the most threatened group of seed plants, with isolation and habitat fragmentation among the primary drivers of species decline. Understanding how genetic diversity is distributed across populations is crucial for informing conservation management and identifying genetically vulnerable populations that require conservation attention.

Methods: Here we investigated the genetic diversity and structure of two endemic Australian species of significant conservation concern, Cycas armstrongii and C. maconochiei subsp. maconochiei. Two hundred and thirty-six individuals were sampled from 26 populations across their native ranges, including a presumed putative hybrid population (C. armstrongii × maconochiei), utilizing next-generation sequencing in the form of restriction site-associated DNA sequencing (RADseq).

Key results: Our results suggested low levels of genetic diversity in both taxa (C. armstrongii, He ≤ 0.038; C. maconochiei subsp. maconochiei, He ≤ 0.061) and no evidence for inbreeding (mean GIS -0.143 and -0.153, respectively). Analysis of molecular variance indicated minimal genetic differentiation between populations (2.41 %) and between taxa (1.81 %). However, pairwise FST values and the Mantel test revealed significant isolation by distance (r = 0.606, P < 0.0001). Discriminant analysis of principal components and popuatlion STRUCTURE analysis indicated admixture, between populations. Morphological traits, principal component and environmental analysis based on seven traits found significant differentiation in five characters, four of which were environmentally linked. The results showed no clear signal of interspecific hybridization for either taxon.

Conclusions: These findings indicate C. armstrongii and C. maconochiei subsp. maconochiei likely represent a morphologically variable species. In addition to updating the threat assessment, we recommend: (1) formally recognizing genetically depauperate or geographically isolated populations (e.g. Tiwi Islands) as conservation management units (CMUs); (2) establishing new ex situ assurance collections for at-risk CMUs; and (3) implementing assisted gene flow among genetically compatible populations to enhance adaptive potential. These actions will ensure conservation strategies are tailored to evolutionary and ecological units.

Background and aims: Macroptilium (Benth.) Urb. is native to regions from North to South America. Phylogenetic analyses place it close to Phaseolus L. beans; however, its infrageneric division into two sections is not well supported. Despite its stability in chromosomal number (2n = 22), interspecific ribosomal DNA loci variation enabled species differentiation, suggesting that a cytogenomic approach might be valuable for inferring species relationships and genome evolution.

Methods: Here, we: (1) characterized nine Macroptilium species through oligonucleotide-based chromosome painting and barcoding (Oligo-FISH); (2) generated genome skimming data for six species and used them to investigate their repeatome dynamics; and (3) performed phylogenomic reconstruction using complete plastomes.

Key results: Oligo-FISH data unveiled de novo translocations between chromosomes 2 and 6, and 3 and 11 in species from proposed groups II and III, respectively, in disagreement with the currently proposed phylogenetic hypothesis. Our phylogenomic (plastid) and repeatome (nuclear) analyses supported groups II and III as clades, with clade-specific satellite DNA families. Group I was paraphyletic and resembled the ancestral Phaseolinae karyotype.

Conclusions: We demonstrated the efficiency of different cytogenomic approaches to characterize Macroptilium species, providing insights into its genomic evolution and indicating the need for a systematic re-evaluation of the genus. These findings also support the power of these approaches to solve phylogenetic relationships even in groups with chromosome number stability and recent diversification.

Background and aims: Hybridization events are crucial in the evolution of plants. Experimental hybridization between extant lineages can help us understand the evolutionary consequences of merging different species. Brassica allohexaploids (2n = AABBCC) offer a unique opportunity to test the effects of hybridization between allopolyploids from different species origins, and specifically whether these new hybrids are fertile and perform better than the parents.

Methods: We hand-pollinated between Brassica allohexaploid genotypes from different species origins to analyse the crossability between species: carirapa (2n = 54; B. carinata × B. rapa), junleracea (B. juncea × B. oleracea), naponigra (B. napus × B. nigra) and NCJ (B. napus × B. carinata × B. juncea). We also analysed a subset of resulting F1 hybrids for fertility and genomic changes.

Key results: We obtained 9052 new allohexaploid hybrid seeds, with a range of 0.0-4.6 seeds per flower bud crossed. Specific female and male parent genotypes affected the crossing success rate (number of seeds/bud crossed). The F1 hybrids showed mid-parent heterosis for seed fertility ranging from -64 to 275 %, while best-parent heterosis ranged from -79 to 241 %. Most of the F1 hybrids had similar quantities of copy number variation (CNV) events compared with the parents, with the majority of these events (76 %) directly inherited from one of the parents.

Conclusions: We conclude that combining different allohexaploid types via hand pollination is feasible without any extra measures to ensure embryo survival, despite the different species origins, with strong maternal genotype effects on success rate. Novel hybrids between allohexaploid lineages showed similar fertility and stability to their parents, suggesting that there is no selection against CNVs in the hybridization event, nor is there an immediate gain in seed fertility associated with an increase in heterozygosity in the allohexaploids.

Background: Costs of reproduction arise from fitness-based trade-offs between current and future reproduction. Because the average fitness of females and males is constrained to be equal, and because costs of reproduction are paid in units of fitness, the extent to which reproductive costs can differ between the sexes has been called into question.

Scope: Using expressions that incorporate the trade-off between current and future reproductive fitness, I examine whether costs of reproduction can in principle differ between the sexes. These expressions clarify the types of evidence that could be used to infer divergence in costs of reproduction between the sexes.

Key results: Costs of reproduction can differ between the sexes only insofar as females and males can diverge in their expected future reproductive potential. If the two sexes differ in their future reproductive potential and one sex prioritizes future opportunities over current output, that sex should experience lower costs of reproduction.

Conclusions: The expected future reproductive potential of plants is driven by their schedules of survival and reproduction, which are difficult to study for long-lived plants. However, it may be possible to infer differences in the costs of reproduction between females and males by combining two pieces of evidence: sex differences in (1) the magnitude of trade-offs between reproduction and growth or survival; and (2) the propensity to produce offspring after previous bouts of reproduction (e.g. via differences in post-reproductive growth or survival). Evidence for (1) and (2) exists widely, but they have rarely been studied together in dioecious populations, leaving little solid evidence regarding how often costs of reproduction differ between females and males.

Background and aims: Many species have both tree and shrub growth forms, and for some, the capacity to shift between single- and multi-stemmed growth can be linked to changing environmental conditions. Such growth-form variability can result from different developmental trajectories of perennial shoots located above- and/or below-ground. Some of these responses are initiated at early life stages and propagate throughout ontogeny. This implies that conditions experienced during early life stages can impose legacy effects at later stages, defining whole-plant ontogenetic trajectories and impacting form. Here, we explore how environmental factors experienced at different stages of ontogeny can influence forms.

Methods: We focus on a generalist species (Handroanthus ochraceus, Bignoniaceae) growing in a range of fire-disturbance and light-availability conditions across tropical forests and savannas.

Key results: Depending on the presence of a disturbance regime experienced early in ontogeny, individuals can develop as either multi- or single-stemmed plants. Importantly, growth-form variability can be induced early in development, probably translating into growth-form plasticity.

Conclusions: We discuss the possible generalization of our observations to other taxa and whether variation in plant form is attributable to genetic differentiation or plasticity. Finally, we call for more studies of woody plant plasticity and how plasticity can be modulated through ontogeny.