Annals of botany最新文献

Background and aims: Pollination failure occurs from insufficient pollen quantity or quality. However, the relative contributions of pollen quantity vs quality to overall pollen limitation, and how this is affected by the co-flowering context, remain unknown for most plant populations. Here, we studied patterns of pollen deposition and pollen tube formation across populations of four predominately outcrossing species in the genus Clarkia to evaluate how richness of co-flowering congeners affects the contribution of pollen quantity and quality to pollen limitation.

Methods: We partition variation in pollen deposition and pollen tube production across individuals, populations and species to identify the main sources of variation in components of reproductive success. We further quantify the relative contribution of pollen quantity and quality limitation to the reproductive success of the four Clarkia species using piecewise regression analyses. Finally, we evaluate how variation in the number of co-flowering Clarkia species in the community affects the strength of pollen quality and quality limitation.

Results: Across all contexts, pollen deposition and the proportion of pollen tubes produced varied greatly among individuals, populations, and species, and these were not always correlated. For instance, C. xantiana received the smallest pollen loads yet produced the highest proportion of pollen tubes, while C. speciosa exhibited the opposite pattern. Yet, co-flowering richness had variable effects on the strength of pollen quantity and quality limitation among populations. Specifically, breakpoint values, which are an indicator of overall pollen limitation, were two times larger in the four-species community compared with one and two-species communities for two Clarkia species, suggesting that pollen limitation can increase with increasing richness of co-flowering congeners.

Conclusions: Our results reveal a complex interplay between quantity and quality of pollen limitation and co-flowering context that may have different evolutionary outcomes across species and populations.

Background and aims: Amphistomy is a potential method for increasing photosynthetic rate; however, the latitudinal gradients of stomatal density across amphistomatous species and their drivers remain unknown.

Methods: Here, the adaxial stomatal density (SDad) and abaxial stomatal density (SDab) of 486 amphistomatous species-site combinations, belonging to 32 plant families, were collected from China, and their total stomatal density (SDtotal) and stomatal ratio (SR) were calculated.

Key results: Overall, these four stomatal traits did not show significant phylogenetic signals. There were no significant differences in SDab and SDtotal between woody and herbaceous species, but SDad and SR were higher in woody species than in herbaceous species. Besides, a significantly positive relationship between SDab and SDad was observed. We also found that stomatal density (including SDab, SDad, and SDtotal) decreased with latitude while SR increased with latitude, and temperature seasonality was the most important environmental factor driving it. Besides, evolutionary history (represented by both phylogeny and species) explained about 10-22 fold more of the variation in stomatal traits than the present-day environment (65.2%-71.1% vs. 2.9%-6.8%).

Conclusions: Our study extended our knowledge of trait-environment relationships and highlighted the importance of evolutionary history in driving stomatal trait variability.

Background and aims: Epichloë endophytes are vertically transmitted via grass seeds and chemically defend their hosts against herbivory. Endophyte-conferred plant defence via alkaloid biosynthesis may occur independently of costs for host plant growth. However, fitness consequences of endophyte-conferred defence and transgenerational effects on herbivore resistance of progeny plants, are rarely studied. The aim of this study was to test whether severe defoliation in mother plants affects their seed production, seed germination rate, and the endophyte-conferred resistance of progeny plants.

Methods: In a field study, we tested the effects of defoliation and endophyte symbiosis (Epichloë uncinata) on host plant (Festuca pratensis) performance, loline alkaloid concentrations in leaves and seeds, seed biomass and seed germination rates. In a subsequent greenhouse study, we challenged the progeny of the plants from the field study to aphid herbivory and tested whether defoliation of mother plants affects endophyte-conferred resistance against aphids in progeny plants.

Key results: Defoliation of the mother plants resulted in a reduction of alkaloid concentrations in leaves and elevated the alkaloid concentrations in seeds when compared with non-defoliated endophyte-symbiotic plants. Viability and germination rate of seeds of defoliated endophyte-symbiotic plants were significantly lower compared to those of non-defoliated endophyte-symbiotic plants and endophyte-free (defoliated and non-defoliated) plants. During six weeks growth, seedlings of defoliated endophyte-symbiotic mother plants had elevated alkaloid concentrations, which negatively correlated with aphid performance.

Conclusions: Endophyte-conferred investment in higher alkaloid levels in seeds -elicited by defoliation- provided herbivore protection in progenies during the first weeks of plant establishment. Better protection of seeds via high alkaloid concentrations negatively correlated with seed germination indicating trade-off between protection and viability.

Background and aims: Roots and rhizomes are critical for the adaptation of clonal plants to soil water gradients. Oryza longistaminata, a rhizomatous wild rice, is of particular interest for perennial rice breeding due to its resilience under abiotic stress conditions. While root responses to soil flooding are well-studied, rhizome responses to water gradients remain underexplored. We hypothesize that physiological integration of Oryza longistaminata mitigates heterogeneous water deficit stress through interconnected rhizomes, and both roots and rhizomes respond to contrasting water conditions.

Methods: We investigated the physiological integration between mother plants and ramets, measuring key photosynthetic parameters (photosynthetic and transpiration rate, and stomatal conductance) using an Infrared Gas Analyzer. Moreover, root and rhizome responses to three water regimes (flooding, well-watered, and water deficit) were examined by measuring radial water loss and apparent permeance to O2, along with histochemical and anatomical characterization.

Key results: Our experiment highlights the role of physiological integration via interconnected rhizomes in mitigating water deficit stress. Severing rhizome connections from mother plants or ramets exposed to water deficit conditions led to significant decreases in key photosynthetic parameters, underscoring the importance of rhizome connections in bidirectional stress mitigation. Additionally, O. longistaminata rhizomes exhibited constitutive suberized and lignified apoplastic barriers, while such barriers were induced in roots under water stress. Anatomically, both rhizomes and roots respond similarly to water gradients, showing thinner diameters under water deficit conditions and larger diameters under flooding conditions.

Conclusion: Our findings indicate that physiological integration through interconnected rhizomes helps alleviate water deficit stress when either the mother plant or the ramet is experiencing water deficit, while the counterpart is in control conditions. Moreover, O. longistaminata can adapt to various soil water regimes by regulating anatomical and physiological traits of roots and rhizomes.

Background and aims: Clonal growth is widespread among herbaceous plants, and helps them to cope with environmental heterogeneity through resource integration via connecting clonal organs. Such integration is considered to balance heterogeneity by translocation of resources from rich to poor patches. However, such an 'equalisation' strategy is only one of several possible strategies. Under certain conditions, a strategy emphasising acropetal movement and exploration of new areas or a strategy of accumulating resources in older ramets may be preferred. The optimal strategy may be determined by environmental conditions, such as resource availability and level of light competition. We aimed to summarise possible translocation strategies in a conceptual analysis and to examine translocation in two species from different habitats.

Methods: Resource translocation was compared between two closely related species from different habitats with contrasting productivity. The study examined the bidirectional translocation of carbon and nitrogen in pairs of mother and daughter ramets grown under light heterogeneity (one ramet shaded) at two developmental stages using stable-isotope labelling.

Key results: At the early developmental stage, both species translocated resources toward daughters and the translocation was modified by shading. Later, the species of low-productivity habitats, Fragaria viridis, translocated carbon to shaded ramets (both mother and daughter), according to the 'equalisation' strategy. In contrast, the species of high-productivity habitats, Potentilla reptans, did not support shaded mother ramets. Nitrogen translocation remained mainly acropetal in both species.

Conclusions: The two studied species exhibited different translocation strategies, which may be linked to the habitat conditions experienced by each species. The results indicate that we need to consider different possible strategies. We emphasise the importance of bidirectional tracing in translocation studies and the need for further studies to investigate the translocation patterns in species from contrasting habitats using a comparative approach.

Background and aims: Leaf variegation is common in plants and confers diverse adaptive functions. However, its genetic underpinnings remain largely unresolved; this is particularly true for variegation that arises through modified leaf tissue structure that affects light reflection. White clover is naturally polymorphic for structure-based white leaf mark variegation. It therefore provides a useful system to examine the genetic basis of this phenotype, and to assess potential costs to photosynthetic efficiency resulting from modified leaf structures. This study sought to map the loci controlling the white leaf mark in white clover and evaluate the relationship between white leaf mark, leaf thickness, and photosynthetic efficiency.

Methods: We generated a high-density genetic linkage map from an F3 mapping population, employing reference genome-based SNP markers. White leaf mark was quantified through detailed phenotypic evaluations alongside leaf thickness to test how tissue thickness may affect the variegation phenotype. Quantitative trait locus (QTL) mapping was performed to characterize their genetic bases. Photosynthetic efficiency measurements were used to test for physiological trade-offs between variegation and photosynthetic output.

Key results: The V locus, a major gene responsible for the white leaf mark polymorphism, was mapped to the distal end of chromosome 5, and several modifier loci were also mapped that contribute additively to variegation intensity. The presence and intensity of white leaf mark was associated with greater leaf thickness; however, increased variegation did not detectably affect photosynthetic efficiency.

Conclusions: We have successfully mapped the major locus governing the white leaf mark in white clover, along with several modifier loci, revealing a complex basis for this structure-based variegation. The apparent absence of compromised photosynthesis in variegated leaves challenges the notion that variegation creates fitness trade-offs between photosynthetic efficiency and other adaptive functions. This finding suggests that other factors may maintain the white leaf mark polymorphism in white clover.

Background and aims: The Labrador Teas (genus Rhododendron, subsection Ledum) are a complex of species widely distributed in the Northern Hemisphere. They occupy cold-resistant plant communities from highlands to forest understory and wetland habitats almost circumboreally and they are especially abundant in Northeast Asia (NE Asia) and northern North America (NN Am), still there are no clear species boundaries in this group. The genetic structure of species of the subsect. Ledum from Eurasia and North America as well as the dispersal history of the group require clarification.

Methods: Phylogeny and biogeography of the subsect. Ledum of the genus Rhododendron were assessed using phylogenetic trees constructed based on the analysis of variation in chloroplast petB-petD, trnV-ndhC, trnH-psbA, K2R-K707, atpB oligo2 - rbcL oligo5 and nuclear (ITS1) markers of four Eurasian and one American species (65 populations, 408 individuals). The data were evaluated with Maximum Parsimony and Bayesian analysis. Molecular dating and ancestral areas reconstruction were obtained.

Key results: Dense sampling revealed widespread presence of shared haplotypes and ribotypes among Ledum populations and species. Two American, three Eurasian and one mixed lineage diversified during the Neogene climate cooling and then rapidly dispersed during the Pleistocene. The ability to accumulate high genetic diversity and to preserve it across distribution ranges and generations prevented Ledum from lineage sorting. As a result, a species complex with a reserve of genetic variability appeared.

Conclusions: Although no clear phylogenetic inference can be obtained at present, the plastid genealogy is consisted with the nuclear genealogy and demonstrates the processes involved in speciation in the Ledum species complex.

Background and aims: Soil endemics have long fascinated botanists due to the insights they can provide about plant ecology and evolution. Often, these species have unique foliar nutrient composition patterns that reflect potential physiological adaptations to these harsh soil types. However, understanding global nutritional patterns to unique soil types can be complicated by the influence of recent and ancient evolutionary events. Our goal was to understand whether plant specialization to unique soils is a stronger determinant of plant nutrient composition than climate or evolutionary constraints.

Methods: We worked on gypsum soils. We analyzed whole-plant nutrient composition (leaves, stems, coarse roots and fine roots) of 36 native species of gypsophilous lineages from the Chihuahuan Desert (North America) and the Iberian Peninsula (Europe) regions, including widely distributed gypsum endemics, as specialists, and narrowly distributed endemics and non-endemics, as non-specialists. We evaluated the impact of evolutionary events and soil composition on the whole-plant composition, comparing the three categories of gypsum plants.

Key results: Our findings reveal nutritional convergence of widely distributed gypsum endemics. These taxa displayed higher foliar Sulfur and higher whole-plant Magnesium than their non-endemic relatives, irrespective of geographic location or phylogenetic history. Sulfur and Magnesium concentrations were mainly explained by non-phylogenetic variation among species related to gypsum specialization. Other nutrient concentrations were determined by more ancient evolutionary events. For example, Caryophyllales usually displayed high foliar Calcium, whereas Poaceae did not. In contrast, plant concentrations of Phosphorus was mainly explained by species-specific physiology not related to gypsum specialization or evolutionary constraints.

Conclusions: Plant specialization to a unique soil may strongly influence plant nutritional strategies, as we described for gypsophilous lineages. Taking a whole-plant perspective (all organs) within a phylogenetic framework has enabled us to gain a better understanding of plant adaptation to unique soils when studying taxa from distinct regions.

Background and aims: Dioecious plant species, i.e., those in which male and female functions are housed in different individuals, are particularly vulnerable to global environmental changes. For long-lived plant species, such as trees, long-term studies are imperative to understand how growth patterns and their sensitivity to climate variability differentially affect the sexes.

Methods: Here, we explore long-term intersexual differences in wood traits, namely radial growth rates, water use efficiency quantified as stable carbon isotope abundance of wood cellulose, and their climate sensitivity in Ilex aquifolium trees growing in a natural population in NW Spain.

Key results: We found that sex differences in secondary growth rates were variable over time, with males outperforming females in both radial growth rates and water use efficiency in recent decades. Summer water stress significantly reduced the growth of female trees in the following growing season, while the growth of male trees was primarily favoured by cloudy and rainy conditions the previous fall and winter combined with low cloud cover and warm conditions in summer. Sex-dependent lagged correlations between radial growth and water availability were found, with a strong association between tree growth and cumulative water availability in females at 30 months and in males at 10 months.

Conclusions: Overall, our results point to greater vulnerability of female tress to increasing drought, which could lead to sex-ratio biases threatening population viability in the future.