Annals of botany最新文献

Background and aims: Since salinity stress may occur across stages of rice (Oryza sativa L.) crop growth, understanding the effects of salinity at reproductive stage is important although it has been much less studied than at seedling stage.

Methods: In this study, lines from the Rice Diversity Panel 1 (RDP1) and the 3000 Rice Genomes (3KRG) were used to screen morphological and physiological traits, map loci controlling salinity tolerance through genome-wide association studies (GWAS), and identify favorable haplotypes associated with reproductive stage salinity tolerance.

Key results: Salt exclusion was identified as the key tolerance mechanism in this study based on reduced panicle length as flag leaf Na+ increased, and a lack of effect of trimming the leaves in the salinity treatment on genotypic rankings. Since larger biomass showed a negative effect on the number of filled grains in multiple experiments, future studies should investigate the effect of whole-plant transpiration levels on salt uptake. In addition to genome-wide significant peaks identified in the single trait GWAS analyses, six loci showed colocations for multiple traits across experiments. Among these co-locating loci, three candidate loci that exhibited favorable haplotypes were also characterized to be involved in co-expression networks among which apoplast and cell wall functions had been annotated - further highlighting the role of salt exclusion.

Conclusion: The loci identified here could be considered as potential sources for improving reproductive stage salinity tolerance in rice.

Background and aims: Fire-released seed dormancy (SD) is a key trait for successful germination and plant persistence in many fire-prone ecosystems. Many local studies have shown that fire-released SD depends on heat and exposure time, dose of smoke-derived compounds, SD class, plant lineage and the fire regime. However, a global quantitative analysis of fire-released SD is lacking. We hypothesized that fire-released SD is more prevalent in fire-prone than in non-fire-prone ecosystems, and in crown-fire compared to surface-fire ecosystems. Additionally, uncovering patterns in the relationship between fire cues and SD classes at the global scale that mirror those identified in local or regional studies was expected.

Methods: Totally, 246 published germination studies during 1970-2022, encompassing 1782 species from 128 families was used in our meta-analysis. Meta-analysis moderators included different fire cues, smoke application methods, smoke exposure duration and concentration, smoke compounds, fire-proneness, fire regimes, and ecosystem types.

Key results: Heat released physical, and smoke released physiological and morphophysiological dormancies. For SD release, heat and smoke acted synergistically, and KAR1 was the most effective smoke compound. Fire-released SD was more prevalent in fire-prone than non-fire-prone regions; and particularly under crown fire regimes. Fire-released SD occurred mainly in Mediterranean ecosystems, temperate dry forests, and temperate warm ecosystems, whereas species from savannas and tropical grasslands, temperate grasslands, and tropical rainforests generally responded negatively to fire.

Conclusions: Fire-released SD is strongly influenced by fire regimes the latter with significant role in shaping SD and germination patterns on a global scale. The synergistic effect of heat and smoke in dormancy release reveals more intricate interactions between fire cues than previously understood. Understanding these patterns is crucial in the context of shifting fire regimes driven by climate change, as they may disrupt plant life cycles, alter ecosystem functions, biodiversity, and community composition and provide key insights for biodiversity conservation and ecological restoration in fire-prone ecosystems.

Background and aims: Nekemias is a small genus of the grape family, with nine species discontinuously distributed in temperate to subtropical zones of the Northern Hemisphere but mostly in East Asia. Previous phylogenetic studies on Nekemias have mainly based on a few chloroplast markers, and the phylogenetic framework and systematic relationships are still highly contested.

Methods: We carried out a systematic framework reconstruction of Nekemias and intra-generic reticulate evolutionary analyses based on extensive single-copy nuclear and chloroplast genomic data obtained by the Hyb-Seq approach, combining genome skimming and target enrichment.

Key results: Both nuclear and chloroplast genomic data strongly support the monophyly of Nekemias with its division into two major lineages from East Asia and North America, respectively. There are strong and extensive topological conflicts among nuclear gene trees and between nuclear and chloroplast topologies within the genus, especially within the East Asian clade.

Conclusions: Rapid radiation through predominant incomplete lineage sorting (ILS) throughout the evolutionary history of the East Asian taxa is supported to explain the relatively high species diversity of Nekemias in East Asia. This study highlights the important role of short periods of rapid evolutionary radiations accompanied by ILS as a mechanism for the complex and fast species diversifications in the grape family as well as potentially in many other plant lineages in East Asia and beyond.

Background and aims: Seed dispersal impacts plant fitness by shaping the habitat and distribution of offspring, influencing population dynamics and spatial genetic diversity. Whether the evolution of dispersal strategies varies across herbaceous life forms (annual, perennial, clonal) is inconclusive. This study examines how seed dispersal strategies vary between annual and perennial populations of Mimulus guttatus (syn. Erythranthe guttata), investigating differences in seedpod orientation and shape, and the probability and distance of seed dispersal.

Methods: We conducted a greenhouse experiment using 190 plants from 6 populations of annual and perennial M. guttatus, to compare floral orientation, seedpod architecture, and its effect on seed dispersal. We used controlled wind trials to measure the probability of seed dispersal and the dispersal distance of individual seeds from plants.

Key results: We identify three key differences in seedpod architecture and seed dispersal in annuals and perennials: seedpods are angled more upward-facing in perennials compared to annuals; a lower proportion of seed is dispersed in perennials; and seed disperse farther in perennials than annuals. These results are consistent with our predictions that a clonal, perennial life form should be associated with traits that increase the retention of seeds, requiring greater wind speeds to dislodge seed and increasing dispersal distance.

Conclusions: Despite the close genetic relationship between annual and perennial populations of M. guttatus, we find differences in seedpod architecture and seed dispersal. We suggest that perennial plants, characterized by clonal reproduction and multi-year survival, benefit from strategies that facilitate long-distance seed dispersal to mitigate competition and promote colonization of new habitats.

Background and aims: In Central Europe, the drought-tolerant downy oak (Quercus pubescens) is at the northern edge of its natural distribution range, often growing in small and spatially isolated populations. Here, we elucidate how the population genetic structure of Central European Q. pubescens was shaped by geographic barriers, genetic drift and introgression with the closely related sessile oak (Q. petraea).

Methods: 27 Q. pubescens populations from the northern margin of Q. pubescens' natural distribution range were sampled. Based on 16 nuclear microsatellite markers (nSSRs), Bayesian clustering and distance-based analyses were performed to determine the intraspecific genetic structure and to identify genetic barriers. To identify drivers of introgression with Q. petraea, generalised linear models were applied to link levels of introgression with environmental conditions. To track post-glacial migration routes, the spatial distribution of haplotypes based on 8 chloroplast microsatellite markers (cpSSRs) was investigated.

Key results: Based on nSSRs, the study populations of Q. pubescens were divided into a western and an eastern genetic cluster. Within these clusters, more pronounced genetic substructure was observed in the west, probably due to a rugged topography and limited gene flow. Introgression from Q. petraea was more prevalent at wetter and north-exposed sites and in the west. The identified cpSSR haplotypes followed known migration pathways.

Conclusions: Our results suggest two late-glacial refugia in or near the southwestern Alps and the southeastern Alps as potential sources for post-glacial migration. Although some genetic exchange is evident in Northern Italy, south of the Alps, the two clusters remain distinct at a large scale. Landscape features and introgression with Q. petraea shaped the genetic substructure at a smaller scale. Our study provides a comprehensive overview of the genetic structure of Q. pubescens in Central Europe, relevant for conservation.

Background and aims: Recent studies have documented numerous morphoanatomical variations for the seed coat in Bromeliaceae. However, the structural diversity and character evolution of the embryo within this family remain largely unexplored. Given the embryo's significance in plant diversification, this research aims to investigate the morphology and key anatomical features of Bromeliaceae embryos, providing insights into character evolution, taxonomic applications, and reproductive biology.

Methods: We analysed samples of 88 species from 50 genera representing the major lineages of Bromeliaceae, using standard plant microtechniques adapted for seeds. To determine ancestral traits, parsimony and maximum likelihood analyses were performed in a consensus supertree combining previous phylogenies.

Key results: This study identified 14 informative characters, highlighting significant differences among groups, particularly in embryo morphology, differentiation, and anatomical traits. Our analysis revealed that undifferentiated embryos with a vestigial cotyledonary hyperphyll are plesiomorphic in Bromeliaceae. They have evolved multiple times into rudimentary or well-differentiated embryos, the latter exhibiting intermediate or large sizes and diverse cotyledonary hyperphyll morphologies. The cotyledonary hypophyll varies in sheath lobes and slit morphologies, and is curved or expanded exclusively in Bromelioideae representatives. Similarly, several patterns of hypocotyl/radicle constriction are unique to Tillandsioideae and plesiomorphic for this clade. Although rudimentary embryos exhibit simpler and more uniform anatomy, they are distinct from undifferentiated embryos, which lack defined organs and internal tissues. In contrast, well-differentiated embryos possess more complex anatomical structures, including a multi-layered shoot apical meristem and root cap, a broad cotyledonary sheath, and often leaf primordia, the latter evolving independently several times only in large embryos.

Conclusions: Our findings reveal a previously unknown morphological diversity for embryos in Bromeliaceae, enhancing our understanding of the morphological evolution of its major lineages. In addition, it introduces new informative characters for the family's systematics and broadens our understanding of the reproductive biology of Bromeliaceae.

Background: The frequency and intensity of droughts are expected to increase under global change, driven by anthropogenic climate change and water diversion. Precipitation is expected to become more episodic under climate change, with longer and warmer dry spells, although some areas might become wetter. Diversion of freshwater from lakes and rivers and groundwater pumping for irrigation of agricultural fields are lowering water availability to wild plant populations, increasing the frequency and intensity of drought. Given the importance of seasonal changes and extremes in soil moisture to influence plant reproduction, and because the majority of plants are flowering plants and most of them depend on pollinators for seed production, this review focuses on the consequences of drought on different aspects of reproduction in animal-pollinated angiosperms, emphasizing interactions among drought, flowering and pollination.

Scope: Visual and olfactory traits play crucial roles in attracting pollinators. Drought-induced floral changes can influence pollinator attraction and visitation, together with pollinator networks and flowering phenology, with subsequent effects on plant reproduction. Here, we review how drought influences these different aspects of plant reproduction. We identify knowledge gaps and highlight areas that would benefit from additional research.

Conclusions: Visual and olfactory traits are affected by drought, but their phenotypic responses can vary with floral sex, plant sex, population and species. Ample phenotypic plasticity to drought exists for these traits, providing an ability for a rapid response to a change in drought frequency and intensity engendered by global change. The impact of these drought-induced changes in floral traits on pollinator attraction, pollen deposition and plant reproductive success does not show a clear pattern. Drought affects the structure of plant-pollinator networks and can modify plant phenology. The impact of drought on plant reproduction is not always negative, and we need to identify plant characteristics associated with these more positive responses.

Background and aims: Genomic changes triggered by polyploidy, chromosomal rearrangements, and/ or environmental stress are among factors that affect the activity of mobile elements, particularly Long Terminal Repeats Retrotransposons (LTR-RTs) and DNA transposons. Because these elements can proliferate and move throughout host genomes, altering the genetic, epigenetic and nucleotypic landscape, they have been recognized as a relevant evolutionary force. Beaksedges (Rhynchospora) stand out for their wide cosmopolitan distribution, high diversity (~400 spp.) and holocentric chromosomes related to high karyotypic diversity and a centromere-specific satDNA Tyba. This makes the genus an interesting model to investigate the interactions between repetitive elements, phylogenetic relationships, and ecological variables.

Methods: Here, we used comparative phylogenetic methods to investigate the forces driving the evolution of the entire set of mobile elements (mobilome) in the holocentric genus Rhynchospora. We statistically tested the impact of phylogenetic relationships, abundance of holocentromeric satDNA Tyba, diversity of repeatome composition, ecological variables, and chromosome number in mobile element diversification.

Key results: Tyba abundance was found to be inversely correlated with LTR-RT content. Decrease of LTR abundance and diversity was also related to increase in chromosome number (likely due to fission events), and colonization of dry environments in the northern hemisphere. In contrast, we found constant LTR insertions throughout time in species with lower chromosome numbers in rainier environments in South America. A multivariate model showed that different traits drive LTR abundance, especially repeat diversity and Tyba abundance. Other mobile elements, such as non-LTR RTs and DNA transposons had insufficient abundance to be included in our models.

Conclusions: Our findings suggest that LTR evolution is strongly impacted by the holocentric characteristics of Rhynchospora chromosomes, correlating with species diversification and biome shifts, and supporting a holokinetic drive model of evolution and a competitive scenario with Tyba. Altogether, our results present evidence of multi-trait influence on LTR-RT dynamics and provide a broader understanding of TE evolution in a macroevolutionary context.

Background and aims: To better understand C4 evolution in monocots, we characterized C3-C4 intermediate phenotypes in the grass genus Homolepis (subtribe Arthropogoninae).

Methods: Carbon isotope ratio (δ13C), leaf gas exchange, mesophyll (M) to bundle sheath (BS) tissue characteristics, organelle size and numbers in M and BS tissue, and tissue distribution of the P-subunit of glycine decarboxylase (GLDP) were determined for five Homolepis species and the C4 grass Mesosetum loliiforme from a phylogenetic sister clade. We generated a transcriptome-based phylogeny for Homolepis and Mesosetum species to interpret physiological and anatomical patterns in an evolutionary context, and to test for hybridization.

Key results: Homolepis contains two C3 (H. glutinosa, H. villaricensis), one weaker form of C2 termed sub-C2 (H. isocalycia), and two C2 species (H. longispicula, H. aturensis). Homolepis longispicula and H. aturensis express over 85% of leaf GDC in centripetal mitochondria within the BS, and have increased fractions of leaf chloroplasts, mitochondria and peroxisomes within the BS relative to H. glutinosa. Analysis of leaf gas exchange, cell ultrastructural, and transcript expression show M. loliiforme is a C4 plant of the NADP-malic enzyme subtype. Homolepis is comprised of two sister clades, one containing H. glutinosa and H. villaricensis and the second H. longispicula and H. aturensis. Homolepis isocalycia is of hybrid origin, with parents being H. aturensis and a common ancestor of the C3  Homolepis clade and H. longispicula.

Conclusions: Photosynthetic activation of BS tissue in the sub-C2 and C2 species of Homolepis is similar to patterns observed in C3-C4 intermediate eudicots, indicating common evolutionary pathways from C3 to C4 photosynthesis in these disparate clades. Hybridization can diversify the C3-C4 intermediate character state and should be considered in reconstructing putative ancestral states using phylogenetic analyses.