Annals of botany最新文献

Background and aims: Drought and salinity are major abiotic factors limiting plant growth in arid regions and always co-occur. However, the response mechanisms of Atriplex canescens to drought and salinity, particularly their coupled stress, remain incompletely understood. To reveal the stress endurance thresholds and facilitate sustainable utilization in arid and saline lands, this research explores various responses of A. canescens to different intensities of drought, salinity and their coupled action.

Methods: A meta-analysis was performed based on research published between January 1970 and September 2025. In this research, we identified light, moderate and severe stress of drought with 60-80, 40-60 and 0-40 % of field water capacity (FWC) and electrical conductivity (EC) ≤ 8, 8-16 and >16 dS m-1 for salinity.

Key results: (1) The drought and salt tolerance thresholds of A. canescens are 0-40 % FWC and >16 dS m-1, respectively. (2) Atriplex canescens increases its root-to-shoot ratio to adapt to increased osmotic potential caused by severe drought and increases proline to cope with increased osmotic potential caused by severe salinity. (3) Coupled drought and salinity stress is more favourable for dry matter accumulation than their single stresses; however, it can intensify ionic toxicity and amplify oxidative stress.

Conclusions: Irrigating A. canescens with an appropriate amount of brackish water can help improve and sustainably utilize salt-affected lands. Still, it is necessary to control ion toxicity and oxidative stress.

Background and aims: Male fertility is often suboptimal in parthenocarpic banana cultivars, hindering their use as male parents in current banana breeding schemes. Next to genotype-specific traits, such as ploidy and structural heterozygosity, inflorescence developmental age and environmental factors can significantly influence male reproductive performance.

Methods: In this study, pollen viability, germination capacity and diameter, were closely monitored throughout the entire male flowering phase of Musa acuminata wild diploids and diploid and triploid cultivars. Additionally, environmental parameters, including temperature, light radiation and humidity, were monitored up to 40 days before anthesis to determine their influence on microgametogenesis.

Key results: Wild accessions showed a gradual reduction in pollen germination over the flowering period. High light radiation prior to pollen mitosis I and II reduced germination capacity, whereas during meiosis it negatively affected pollen viability. Conversely, in cultivated bananas, pollen traits improved with the developmental age of the male inflorescence. In these cultivars, higher temperatures during meiosis enhanced pollen diameter, viability and germination rates.

Conclusions: These findings indicate that both inflorescence maturity and specific environmental conditions during pollen development significantly influence pollen quality in bananas. Pollen performance could be optimized in wild diploids by obtaining pollen in the first months of the male flowering phase and shielding the plants from high light intensities, whereas for cultivars the pollen should be harvested towards the end of the male flowering phase, and a heat treatment during meiosis could lead to higher pollen quality and thereby increase breeding success.

Background and aims: Cell wall invertases (CWIs) are pivotal enzymes in plant sugar metabolism, regulating growth, development, and responses to environmental stresses. Although significant progress of CWIs has been made in some plants, their specific roles in soybean remained largely unexplored.

Methods: In this study two highly homologous CWI genes, GmCWI11 and GmCWI12, were overexpressed in Glycine max (Soybean) and their functional redundancy and differentiation were investigated.

Key results: We demonstrated that overexpression of either gene significantly improved soybean growth performance, including increased plant height, pod number, and seed weight at maturity. Additionally, seed quality traits such as soluble sugars, starch, protein, and fatty acid compositions were markedly enhanced. Transcriptomic analysis uncovered distinct regulatory mechanisms. GmCWI11 predominantly modulated stress-related gene expression, while GmCWI12 primarily influenced genes involved in transmembrane transport. Further, predictions of protein-protein interactions suggested differential regulation by invertase inhibitors.

Conclusions: These findings provide novel insights into the specific roles of CWIs in soybean and identify potential genetic targets for enhancing crop yield and quality through targeted breeding efforts.

Background and aims: Pathogenesis-Related 1 (PR-1) proteins are small, secreted proteins that typically accumulate upon pathogen attack and serve as hallmarks of plant immune activation. Despite their widespread use as defense markers, their biochemical properties and native structural features remain largely unresolved. This study aimed to isolate, characterize, and determine the crystal structure of a native PR-1 protein (MsPR-1b) that predominates in the floral nectar of Mucuna sempervirens, a woody leguminous vine, to provide insight into the molecular diversity and possible functional specialization of PR-1 proteins.

Methods: MsPR-1b was purified from raw nectar using ion-exchange and size-exclusion chromatography. The purified protein was analyzed for molecular mass and glycosylation status, and its three-dimensional structure was determined by X-ray crystallography at 2.0 Å resolution. The full-length cDNA sequence was obtained through RACE PCR, and tissue-specific expression was examined by quantitative PCR. Lipid-binding ability and antimicrobial activity were assessed by fluorescence spectroscopy and the disk diffusion method, respectively.

Key results: The MsPR-1b gene encodes a 164-amino-acid precursor containing an N-terminal signal peptide. Expression was predominantly detected in the nectary. The mature MsPR-1b is a small, basic, secreted protein (15,134 Da, pI 9.4) that lacks glycosylation. The crystal structure, representing the first native PR-1 protein purified from its natural source revealed a homodimer. Each monomer adopts the conserved α-β-α sandwich fold characteristic of the CAP superfamily and contains two intrachain disulfide bonds. MsPR-1b displays no detectable lipid-binding capacity or direct antimicrobial activity.

Conclusions: MsPR-1b provides the first structural view of a native plant PR-1 protein and indicates that nectar-secreted PR-1s may perform specialized, non-defensive functions distinct from canonical pathogen-related roles.

Background and aims: Plant-pollinator interactions span a continuum from strict specialisation to generalisation and most flowers are visited by more than a single functional group of pollinators. However, one functional group might be more efficient than the others and thus exert stronger selective pressure on floral traits. In this study we aim at identifying the evolutionary drivers of floral syndromes in the genus Aquilegia.

Methods: We analyse floral syndromes using multivariate statistics, morphospace analyses, as well as a machine learning approach (random forests), testing for the association between floral traits and documented pollinators for 28 Aquilegia species. In particular, we test whether pollen-collecting pollinators (small bees, large bees, syrphid flies) and nectar-collecting pollinators (large bees, hummingbirds, hawkmoths) are associated with specific floral traits. Furthermore, we test whether mixed pollination systems are reflected in floral syndrome properties.

Key results: Our results indicate that floral syndromes in Aquilegia are mainly shaped by nectar-collecting pollinators (and not by pollen-collecting pollinators). Flowers pollinated by large bees are mostly pendent and short-spurred; hummingbird flowers are red, with constricted spurs and short petal blades; and hawkmoth flowers are erect with long and slender spurs. Flowers pollinated by two groups of nectar-collecting pollinators show syndromes corresponding to only one of their pollinator groups.

Conclusions: Despite their ubiquity, we did not find cues for selection by any of the pollen-collecting pollinators. Nevertheless, selection for traits associated with pollen-collecting pollinators, such as openly accessible stamens and a contrasted yellow floral centre (almost always present in Aquilegia), cannot be ruled out. In conclusion, floral syndromes in Aquilegia are associated with nectar-collecting pollinators only, maybe because they are more efficient at pollinating, which remains to be tested in field experiments.

Background and aims: Large-scale agriculture has altered natural ecosystems, affecting nutrient availability for native plants. Nitrogen is often supplemented in the oligotrophic soils of the Cerrado with industrial fertilizers. Studies show that nitrogen can accumulate at the edges of native fragments near monocultures. However, research linking fragment size to nitrogen availability and plant physiological responses in Cerrado remains scarce. This study examined whether monocultures adjacent to Cerrado fragments introduce industrial nitrogen into conservation areas, and how it influences the physiological leaf traits of the native species, Bauhinia holophylla.

Methods: The study was conducted during the 2022 and 2023 rainy seasons, in Cerrado fragments (16-12,500 ha) adjacent to monocultures. Seven areas were sampled in 2022, with an additional area included in 2023. Sampling points were placed at fragment edges and interiors. Soil samples and B. holophylla leaves were analyzed for δ15N isotopic signature to compare enrichment between edges and interior. In the Panga Ecological Reserve (REP), functional leaf traits of B. holophylla leaves were assessed, including specific leaf area, relative water content, chlorophyll content, potential quantum yield (Fv/Fm), PSII quantum yield (ФPSII), fluorescence decline ratio (Rfd), and non-photochemical quenching (NPQ).

Key results: The soil and leaf δ15N values were higher at the edge than interior of the fragment. Although differences in δ15N values were observed among the fragments, there was no relationship with fragment size. Physiologically, B. holophylla individuals at the edges displayed higher specific leaf area and relative water content, whereas interior plants showed greater Rfd and NPQ. No differences were observed for chlorophyll content, Fv/Fm, and ФPSII.

Conclusions: The findings suggest δ¹⁵N enrichment at the edges of the fragments due to industrial fertilizers. This nitrogen enrichment alters the leaf physiology of B. holophylla, indicating complementary adaptive strategies to maintain photosynthetic performance across different environmental conditions.

Background and aims: Although almost 40% of the world's plant species are likely rare, little is known about the determinants of range size, a major axis of rarity, particularly in the tropics. Narrow geographic ranges make species more susceptible to extinction, so understanding factors that correlate with small range sizes is key to prioritising conservation efforts. The niche breadth - range size hypothesis predicts range restricted species to have narrow environmental tolerances. Here, we tested the niche breadth - range size hypothesis in two big tropical plant genera, Solanum and Begonia.

Methods: We used taxonomically verified occurrence data to quantify the range size of 1,065 species native to Southern America, calculated their climatic niche breadth based on six bioclimatic variables, and used spatial null models to determine whether the observed niche breadth - range size relationship differed significantly from spatial autocorrelation.

Key results: The correlation between climatic niche breadth and range size did not differ significantly from null expectations in either genus. Range-restricted species across both genera occur at higher elevations and have narrower elevational ranges than widespread species, however. More than two-thirds of the species had their minimum niche breadth in temperature seasonality, with strong increases between range-restricted and widespread species, suggesting that niche breadth in terms of temperature seasonality plays a key role in shaping species distributions.

Conclusions: Our findings support the view that niche breadth and range size correlations can artificially arise just from spatial autocorrelation. Macroclimatic conditions capture only a part of the ecological niche, and additional niche properties such as adaptations to soil and fire and biotic interactions are likely to influence species' ranges in particularly in species diverse tropical groups. Our findings emphasise that tropical mountains such as the Andes and the Atlantic forests of Brazil are globally important centres of range-restricted plant species.

Background and aims: Lignin and other phenolics are commonly observed at the interfaces between the haustoria of parasitic plants and tissues of their hosts. As known plant defence compounds, their accumulation at haustorial interfaces has been ascribed to mechanical and chemical resistance of host tissues. Although the possibility that the interfacial lignin deposits may have a parasitic origin has not previously been addressed, the fact that certain parasitic plants, including Rhinanthus and Odontites, can form haustoria in the absence of hosts gives us a tool that can be used to help answer this question.

Methods: We compared the interfaces of haustoria of root hemiparasites yellow rattle Rhinanthus minor and red bartsia Odontites vernus (Orobanchaceae) attached to hosts bulbous oat-grass Arrhenatherum elatius ssp. bulbosum and perennial rye grass Lolium perenne (Poaceae) with the contact surfaces of non-infective prehaustoria attached to a pot surface. We performed histochemistry, immunocytochemistry and Raman spectroscopy to characterize the architecture of contact deposits formed by both.

Key results: Lignolic deposits, which we will term lignin-rich interfacial deposits (LIDs), were found at the interfaces between haustoria and compatible hosts as well as at the pot-appressed facets of prehaustoria. In both cases the deposits were determined as lignin by histology and Raman spectroscopy. Xyloglucan and arabinogalactan protein glycan epitopes were also detected while mixed-linkage glucan, xylans and pectin were not. We demonstrate that prehaustoria can produce lignolic interfacial deposits of high structural similarity to those of haustorium-host interfaces.

Conclusions: LIDs at haustorium-host interfaces may at least partly be attributed to the parasite and benefit the establishment and functioning of the haustorium. A reinterpretation of the origin and role of interfacial lignin in parasitic plant-host interactions may therefore be necessary.