Annals of botany最新文献

Background and aims: In herbaceous peony, the proliferate flower pattern exhibits a complex and two-layered floral structure with high ornamental value, offering new insights into flower development. The development of proliferate flowers is not well understood owing to their complex structure. The aim of this study was to decode the developmental pattern of proliferate flowers through continuous observations of flower bud differentiation, focusing on the morphological and anatomical characteristics of pistils and stamens in proliferate flowers.

Methods: Floral differentiation in herbaceous peonies (including single flower variety, double flower variety and four proliferate flower varieties) was observed using a stereomicroscope, paraffin sectioning and free-hand sectioning. A qRT-PCR experiment was conducted to detect the expression of genes related to floral development, revealing key genes involved in proliferate flower development.

Key results: In proliferate flowers, the development of lower and upper flowers occurs through two distinct stages. The lower flower sequentially generates bracts, sepals, petals, stamens and pistils. On the inner side of pistil primordia, a new flower primordium differentiates continuously to produce the upper flower, retaining characteristics of carpels. The expression levels of classical ABCDE model genes (PlAP1, PlPl2, PlAP3, PlSEP1 and PlSEP3) were higher in proliferate flowers. In contrast, expression of the C-class gene PlAG was reduced in double flowers and was the lowest in proliferate flowers compared with single flowers.

Conclusions: The proliferate flower, a special type of double flower pattern, can be divided into upper and lower flowers. For lower flowers, the varying degrees of petaloid stamens are attributed to the diversity of proliferate flower cultivars, while the proliferation and directional mutation of pistils lead to the origination of upper flowers. For upper flowers, differentiation of the floral apical meristem includes petals, stamens and pistils. The limited expression of PlAG suggests its involvement in the induction of proliferate flowers.

Background and aims: Phenotypic plasticity and bet hedging are mechanisms that can facilitate population persistence in variable environments. In plants, the timing of seed germination can be responsive to reliable environmental cues as well as a mechanism for spreading risk when post-germination conditions are difficult to predict. The goal of this study was to quantify and compare plasticity and potential bet hedging in the timing of seed germination in three closely related species that segregate across a fine-scale gradient in hydrological variability.

Methods: We conducted a growth chamber experiment that measured variation in seed germination within and among three species of Lasthenia (Asteraceae) that occupy different microhabitats along gradients in soil moisture variability in California vernal pool grasslands. We measured the timing of germination in sibling seed groups from each species under two different moisture regimes to characterize the mean and variability in seed germination timing in response to consistent, high moisture and low, variable moisture conditions.

Key results: Germination of viable seeds was extremely high (∼98 %) across all species and treatments. All three taxa showed strong plasticity in response to water treatment by germinating faster with higher, more consistent moisture availability. The two species from higher topographic positions in vernal pool grasslands had greater within-season variance in germination timing, consistent with increased bet hedging, than the deep pool specialist. The extent of within-season bet hedging in these two species was largest in the drier and more variable water treatment, revealing phenotypic plasticity in the extent of bet hedging expressed by these species.

Conclusions: This work supports the hypothesis that plasticity and bet hedging in seed germination timing are favoured in variable and unpredictable environments, and that these strategies can evolve rapidly in association with habitat divergence among closely related species.

Background and aims: Millet crops in the grass genus Digitaria include white and black fonio (D. exilis and D. iburua), raishan (D. compacta) and Polish millet (D. sanguinalis), cultivated across West Africa, India and Europe. Fonio and raishan crops are important in supporting food security and subsistence agricultural systems in rural communities, while D. sanguinalis is no longer cultivated. These crops are resilient to challenging climates. We aim to produce an integrated study of these crops: a phylogeny of the Digitaria genus including all four food species, to identify key crop wild relatives; time-calibrated biogeographic analysis, to investigate the history and evolution of Digitaria; and a morphological study to assess the transition between wild and domesticated species.

Methods: We use the Angiosperms353 target-enrichment sequencing approach to produce maximum likelihood and coalescent model nuclear phylogenies for 46 Digitaria species, and Bayesian methods to propose an evolutionary and biogeographic history for the genus. Morphology of wild and cultivated species is investigated for spikelets and growth habits using microscopy and SEM imaging.

Key results: Four distinct evolutionary lineages are found for the Digitaria crops, and we identify new close crop wild relatives D. fuscescens, D. atrofusca, D. setigera, D. radicosa, and D. ciliaris. South and eastern Africa is proposed as a likely origin of early Digitaria divergence, with crop lineages diverging from wild relatives around 2-6 mya. Incomplete domestication traits are observed, including the loss of trichomes, but no clear change in appearance for spikelet or abscission zone morphologies.

Conclusions: The knowledge produced in this study about Digitaria crop wild relatives will be useful in improving crop traits through targeted breeding and physiological studies, and we also highlight the need for conservation of seed material through programmes working with local partners for these important climate-tolerant indigenous cereals.

Background and aims: Cell wall invertases have multiple roles in plant growth and development, yet their biological functions in seed oil production are still not understood.

Methods: In the present study, the Oryza sativa (rice) cell wall invertase gene OsGIF1 (GRAIN INCOMPLETE FILLING 1) was ectopically expressed in Glycine max (soybean), and its functions in grain yield and seed nutrition were investigated.

Key results: We found that constitutive expression of OsGIF1 significantly improved biomass production, grain yield and seed nutrition in transgenic plants. The contents of protein and starch were significantly increased without dramatic alteration in the content of oil in the seeds of transgenic plants. In addition, the contents of histidine, tryptophan, asparagine, glutamine, palmitic acid and linoleic acid were increased, whereas the contents of oleic acid and linolenic acid were decreased. Further transcriptomic analyses in transgenic plants showed that genes associated with sugar and hormone metabolism were dramatically upregulated.

Conclusions: Our findings offer direct evidence for the potential usage of this gene in the genetic breeding of oil crops with improved grain yield and nutrition.

Background and aims: Tecticornia is the most species-rich genus within the tribe Salicornieae. These halophytes are distributed across the Australian continent along coastlines and inland salt lake shores, playing a key ecological role in these hostile habitats. However, species delimitation within the genus remains controversial and little is known about infrageneric phylogenetic relationships. Therefore, the primary aim of this study was to infer the evolutionary history of Tecticornia and to genetically assess the reliability of current species concepts.

Methods: We sampled multiple accessions per taxon from nearly all currently recognized species in Australia. We used a target enrichment approach with two bait sets: Angiosperms353 and a custom Salicornieae bait set (Salibaits). Analyses were performed using HybPiper, and we addressed paralogy using a tree-based approach. In addition, we tested the potential influence of missing data and/or missing gene trees on the topology of the final phylogenetic tree.

Key results: Despite extensive gene tree discordance and the presence of short branches, the customized Salibaits set consistently produced better-resolved trees than the Angiosperms353 bait set. Missing data were found to have a negligible effect on the final tree inference. These data highlight that there is genetic support for lineages in line with observed morphological variation, suggesting markedly more taxon diversity than is currently circumscribed. While we have shown there is genetic evidence to support the characterization of several new species awaiting formal description, it is clear that further molecular and morphological investigation is required to resolve continent-wide species aggregates, each comprising multiple novel taxa.

Conclusions: The target enrichment method effectively addressed the challenges of species delimitation in Tecticornia posed by reduced morphology and high ecological plasticity. We have shown that while there are several complexes constituting variants widely distributed across the Australian continent, some well-defined taxa have highly restricted distributions, which may represent conservation priorities.

Background and aims: The study of morphological diversity (i.e. disparity) offers unique opportunities to understand evolutionary patterns and processes. Plant disparity studies reveal that morphological disparification can be related to factors such as secondary woodiness or to pollination niche, for example. Similarly, some pollen traits are known to be shaped by environmental pressures, but this influence has only been evaluated in monads, never in multi-grained dispersal units. In this study, we investigated the disparity of aggregated dispersal units in two lineages of Neotropical mimosoid legumes. The Mimosa and Stryphnodendron clades are independent lineages that share similarities in pollen morphology and biome shifts. In this context, we asked: what are the patterns of pollen disparity in these lineages, and are these patterns similar between lineages occurring in the same biomes?

Methods: To answer these questions, we compiled data from the literature on pollen morphology and biomes of occurrence for a phylogenetically representative set of taxa in the Mimosa and Stryphnodendron clades. With these data, we calculated morphospaces and disparity metrics, and tested whether the pollen morphology of distinct lineages occurring in the same biome differs significantly.

Key results: Our results show that Mimosa and Stryphnodendron clades exhibit distinct patterns of pollen disparity, as do independent lineages occurring in the same biomes. Additionally, we observed that certain biomes support greater or lesser levels of morphological disparity.

Conclusions: We conclude that (1) the Mimosa clade has greater disparity, possibly due to evolution of novel pollen morphologies in the genus Mimosa, (2) there is a maintenance of similarities in the pollen of the Stryphnodendron clade, Adenopodia and Piptadenia, and (3) the evolution of pollen grains in these groups appears to be primarily shaped by phylogeny and developmental constraints, with environmental pressures playing a comparatively small role.

Background: Advances in DNA sequencing technology have led to a rapid increase in the number of species with organelle genomes and even complete nuclear genomes being sequenced. Thousands of plastid genomes from across all major clades of land plants are now available, and one of the surprising findings is the recurring event of complete or functional loss of genes involved in cyclic electron transport during photosynthesis, i.e. the ndh genes that encode subunits of the chloroplast NADH dehydrogenase-like (NDH) complex. Gene loss in non-photosynthetic, heterotrophic plants might be expected, but the increasing number of losses being discovered in autotrophic plants calls into question the role and potential dispensability of the ndh genes and the entire NDH complex.

Scope: With a focus on autotrophic plants, the present review compiles published evidence about the loss of both plastid and nuclear encoded NDH genes, providing an overview spanning all major clades of land plants. Current knowledge about the function of NDH and the possible reasons behind repeated loss are discussed.

Conclusions: More than 100 independent events of plastid ndh gene loss have been reported from autotrophic land plants, and strong evidence exists that these losses go hand in hand with the loss of nuclear encoded NDH genes. Although loss is almost inevitable in heterotrophic plants and common among carnivorous plants, it occurs in what appears to be a random manner among normal, autotrophic plants. No single underlying reason for the events of loss can be discerned, although a link to nutrient acquisition prevails. Even in autotrophic plants, the NDH complex might simply be dispensable owing to the existence of an alternative and major pathway of cyclic electron transport around photosystem I.

Background and aims: The moss peristome regulates spore release via the hygroscopic movements of the articulated teeth over the capsule mouth. The presence of hydrophobic material inside the teeth has been sporadically reported, with different names and compositions proposed, and it was thought to cause hygroscopic movements. Here we investigated the origin, characteristics and function of this deposition, now termed the interlamellar lipophilic layer (ILL), with the aim of understanding it and its contribution to peristome hygroscopic movements.

Methods: The ontogeny of the ILL in Dicranum scoparium was elaborated using histology and transmission electron microscopy. Histological, structural and physiological analyses of peristomes were conducted in 14 species of Bryopsida.

Key results: The ILL is formed simultaneously with the deposition of secondary thickenings in the developing peristome. In mature peristomes, the ILL resembles the cuticular layer of plant cuticles. The ILL is present in peristomes with single and double rings of teeth and its absence in three species was confirmed. The responses of the teeth under dry and humid conditions combined with the presence or absence of the ILL led us to reconsider its influence on the hygroscopic movements.

Conclusions: The presence of a polyester layer in moss peristome teeth is confirmed. We named it the interlamellar lipophilic layer (ILL). The absence of the ILL was revealed in three of the 14 species investigated. We confirm that hygroscopic movements occur when the ILL is present or absent. When the ILL is present the peristome teeth remain erect, whereas when it is absent the teeth are reflexed. These findings led us to hypothesize that the ILL influences the amplitude of movements rather than causing them, playing a regulatory role in the gradual dispersal of spores. The species that lacked the ILL were xerophytic, which may represent a novel spore dispersal strategy.

Background: Pollination syndromes are typically defined as idealized pollination modes based on a canonical set of traits. As such, they are often criticized as typological rather than empirical. These syndromes are attributed to the great Italian botanist Federico Delpino, who has borne some blame for their perceived shortcomings. Yet Delpino's original contribution, although it inspired the concept of pollination syndromes, differed significantly from it. What he proposed was, in contrast, an empirical classification of plants into floral functional types (FFTs), with pollination vector as the key trait.

Perspective: Delpino produced two functional type classifications. The first was published, approvingly, by H. Müller in 1873. This was the classification that, in the 20th century, evolved into the pollination syndrome concept. Delpino later proposed a more ambitious and innovative classification of animal pollination into 47 functional types in his monumental work, the Ulteriori Osservazioni. Müller strongly criticized this classification, but if Delpino's second scheme had been refined rather than dismissed, it might have shaped later developments in pollination biology in a highly beneficial way. As Löw wrote in 1895, it was 'one of the most ingenious and grand attempts' at a fundamentally open-ended problem. Müller proposed his own classification in 1881, but after that, interest in floral functional types in pollination ecology languished, eventually to be replaced by a different concept, that of pollination syndromes. In contrast, plant functional type (PFT) classification has become central in vegetation and global change ecology.

Conclusion: Pollination ecology could usefully reflect on the PFT approach, even revisiting Delpino's work (which has never been translated from the original Italian) for inspiration. For some studies, an FFT approach, as pioneered by Delpino, could usefully replace a pollination syndrome-based approach.