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Flowers on the tree of life
\"Genetic and molecular studies have recently come to dominate botanical research at the expense of more traditional morphological approaches. This broad introduction to modern flower systematics demonstrates the great potential that floral morphology has to complement molecular data in phylogenetic and evolutionary investigations. Contributions from experts in floral morphology and evolution take the reader through examples of how flowers have diversified in a large variety of lineages of extant and fossil flowering plants. They explore angiosperm origins and the early evolution of flowers and analyse the significance of morphological characters for phylogenetic reconstructions on the tree of life. The importance of integrating morphology into modern botanical research is highlighted through case studies exploring specific plant groups where morphological investigations are having a major impact. Examples include the clarification of phylogenetic relationships and understanding the significance and evolution of specific floral characters, such as pollination mechanisms and stamen and carpel numbers\"-- Provided by publisher.
Book
Use of microstructural characteristics of pollen and pistil to identify olive cultivars in Southern Brazil
The olive crop has a large diversity in cultivars around the world, whose identification have been based on leaf, stem or fruit traits. However, these traits may be influenced by the environment, which has led to the misidentification of cultivars. The variability of the pistil and pollen structure under electron scanning and light microscopy were studied using the cultivars 'Arbequina', 'Arbosana', 'Frantoio', 'Koroneiki', 'Manzanilla de Sevilla' and 'Picual', cultivated in Southern Brazil. The aim was to find unique patterns for their identification. This type of study has not been carried out in the conditions of Southern Brazil, where the identification of commercial cultivars sometimes is complex and confusing. There were significant differences in the variables, showing uniformity within each cultivar in different locations. The principal component analysis indicated a separation of cultivars according to similarities or micromorphological differences in the pollen wall, area of the lumen and the structural elements of the tectum. For the analysis of the pistil, the separation was even clearer, each cultivar individually forming a cluster, using as characters the length of the style in contrast to the length, width and area of the stigma. This evidenced little variation among individuals within the same cultivar. The information provided can contribute to the individual identification of very close olive tree cultivars in the conditions of Southern Brazil.
Journal Article
B- and C-class gene expression during corona development of the blue passionflower (Passiflora caerulea, Passifloraceae)
Premise of study: The origin of the passionflower corona, a complex series of structures between the petals and stamens, has intrigued botanists for centuries, but has proven intractable using traditional approaches. Supplementing developmental data with expression analyses of three floral identity genes, we test whether the corona in Passiflora caerulea (blue passionflower) is homologous to petals or stamens or whether an alternative hypothesis of the corona as a novel structure is supported. Methods: Corona development was investigated using scanning electron microscopy. Expression of the P. caerulea B-class genes PISTILLATA (PcPI) and TOMATO MADS6 (PcTM6), and C-class gene AGAMOUS (PcAG) was investigated using a combination of RT-PCR and mRNA in situ hybridization analyses. Key results: Corona development starts as a ring of tissue at the base of petals. The outer radii and operculum initiate first at the periphery, followed by the inner radii and pali toward the center, and finally an annulus beneath the operculum. Late in development, a limen, the innermost component of the corona, develops from the side of the androgynophore. RT-PCR analyses indicate that the B-class genes PcPI and PcTM6 and C-class gene PcAG were all expressed in mature coronas. However, mRNA in situ hybridization analyses revealed complex temporal patterns of gene expression in the different corona elements. Conclusions: Our data support the hypothesis that the corona is a composite structure, with the radii, pali, and operculum homologous to stamens, and the limen, which only expresses PcTM6, considered to be a novel structure distinct from the androgynophore.
Journal Article
Flowers on the Tree of Life
Genetic and molecular studies have recently come to dominate botanical research at the expense of more traditional morphological approaches. This broad introduction to modern flower systematics demonstrates the great potential that floral morphology has to complement molecular data in phylogenetic and evolutionary investigations. Contributions from experts in floral morphology and evolution take the reader through examples of how flowers have diversified in a large variety of lineages of extant and fossil flowering plants. They explore angiosperm origins and the early evolution of flowers and analyse the significance of morphological characters for phylogenetic reconstructions on the tree of life. The importance of integrating morphology into modern botanical research is highlighted through case studies exploring specific plant groups where morphological investigations are having a major impact. Examples include the clarification of phylogenetic relationships and understanding the significance and evolution of specific floral characters, such as pollination mechanisms and stamen and carpel numbers.
eBook
Variations in the morphology of Hibiscus rosa-sinensis crested peach flowers in nature
Hibiscus rosa-sinensis has a wide variety of flowers. The variations even can be observed in one hybrid only. The hybrid is known as crested flower (double type I), one of four categories of H. rosa-sinensis flower shapes in nature. This study purpose was to categorize the variation in crested flowers based on morphological observation using 200 samples. The observations showed the form of crested peach could be divided into three groups: crested peach that resembles a single flower (crested single-like), which resembles a double flower (crested double-like), and a transitional between single-like and double-like flower (crested intermediate-like). Groupings are based on the length of the staminal column which measured at the closest distance between the corolla position and the additional stamen or petal. The length of the staminal column on a crested single-like is more than 4 cm (a > 4 cm), whereas the crested double-like is less than 1 cm (a < 1 cm), and the crested intermediate-like is 1-4 cm (1 ≤ a ≤ 4). Groupings are also reinforced by comparing the average number of staminodium petaloid, stamen-petal intermediate, and stamen. The crested single-like has a 1:2:2 ratio, the crested intermediate-like has a 2:1:1 ratio, while the crested double-liked has a 5:1:1 ratio. Of the total 200 crested samples used in the study, 89.5 % of them had intermediate-like forms, while 6.5 % were double-like, and 4 % single-like. It can be concluded that the real crested of H. rosa-sinensis is an intermediate-like form.
Journal Article
Genetic architecture of floral traits in bee- and hummingbird-pollinated sister species of Aquilegia (columbine)
Interactions with animal pollinators have helped shape the stunning diversity of flower morphologies across the angiosperms. A common evolutionary consequence of these interactions is that some flowers have converged on suites of traits, or pollination syndromes, that attract and reward specific pollinator groups. Determining the genetic basis of these floral pollination syndromes can help us understand the processes that contributed to the diversification of the angiosperms. Here, we characterize the genetic architecture of a bee-to-hummingbird pollination shift in Aquilegia (columbine) using QTL mapping of 17 floral traits encompassing color, nectar composition, and organ morphology. In this system, we find that the genetic architectures underlying differences in floral color are quite complex, and we identify several likely candidate genes involved in anthocyanin and carotenoid floral pigmentation. Most morphological and nectar traits also have complex genetic underpinnings; however, one of the key floral morphological phenotypes, nectar spur curvature, is shaped by a single locus of large effect.
Journal Article
Long-term morphological stasis maintained by a plant–pollinator mutualism
Many major branches in the Tree of Life are marked by stereotyped body plans that have been maintained over long periods of time. One possible explanation for this stasis is that there are genetic or developmental constraints that restrict the origin of novel body plans. An alternative is that basic body plans are potentially quite labile, but are actively maintained by natural selection. We present evidence that the conserved floral morphology of a species-rich flowering plant clade, Malpighiaceae, has been actively maintained for tens of millions of years via stabilizing selection imposed by their specialist New World oil-bee pollinators. Nine clades that have lost their primary oil-bee pollinators show major evolutionary shifts in specific floral traits associated with oil-bee pollination, demonstrating that developmental constraint is not the primary cause of morphological stasis in Malpighiaceae. Interestingly, Malpighiaceae show a burst in species diversification coinciding with the origin of this plant–pollinator mutualism. One hypothesis to account for radiation despite morphological stasis is that although selection on pollinator efficiency explains the origin of this unique and conserved floral morphology, tight pollinator specificity subsequently permitted greatly enhanced diversification in this system.
Journal Article
Nectar accessibility determines fitness, flower choice and abundance of hoverflies that provide natural pest control
In modern agricultural landscapes, many organisms providing ecosystem services such as pollination and natural pest control are likely constrained by shortage of nectar and/or pollen required for adult nutrition. More and more flower‐rich field margin strips and other habitats are created to eliminate these constraints. For most target organisms, however, it is not well known which (types of) flowers are effective in providing suitable pollen and nectar. We studied the suitability of a wide range of flowers as a food source for zoophagous hoverflies (hoverflies with predatory larvae) at five different levels: nectar accessibility (based on flower morphology), realized adult fitness, flower choice (both based on cage experiments), flower visitation and hoverfly abundance in mixed vegetation (both based on field observations). Realized survival of Episyrphus balteatus is related to effective flower depth by a sigmoid function. The critical flower depth is 1·6 mm, which is less than the proboscis size of the hoverfly. For Asteraceae, the critical floret depth is even less than 1·0 mm, which – in contrast to common knowledge – rules out most species within this family. Both flower choice in the laboratory and flower visitation rates in the field are well correlated with nectar accessibility and realized adult survival. In mixed floral vegetation, the number of zoophagous hoverflies is highly correlated with the abundance of only those flowers that have accessible nectar for these hoverflies. Synthesis and applications. This comparative study demonstrates that nectar (and not pollen) accessibility is the main driver determining flower resource suitability, flower choice and abundance of zoophagous hoverflies in arable field margins. The study identifies the limited range of plant species that can effectively support these beneficial insects. Preserving the right flowers in and around agricultural fields could enhance local populations and the pest control and pollination services they provide.
Journal Article
Global patterns and a latitudinal gradient of flower disparity
• Morphological diversity (disparity) is an essential but often neglected aspect of biodiversity. Hence, it seems timely and promising to re-emphasize morphology in modern evolutionary studies. Disparity is a good proxy for the diversity of functions and interactions with the environment of a group of taxa. In addition, geographical and ecological patterns of disparity are crucial to understand organismal evolution and to guide biodiversity conservation efforts.
• Here,we analyse floral disparity across latitudinal intervals, growth forms, climate types, types of habitats, and regions for a large and representative sample of the angiosperm order Ericales.
• We find a latitudinal gradient of floral disparity and a decoupling of disparity from species richness. Other factors investigated are intercorrelated, and we find the highest disparity for tropical trees growing in African and South American forests.
• Explanations for the latitudinal gradient of floral disparity may involve the release of abiotic constraints and the increase of biotic interactions towards tropical latitudes, allowing tropical lineages to explore a broader area of the floral morphospace. Our study confirms the relevance of biodiversity parameters other than species richness and is consistent with the importance of species interactions in the tropics, in particular with respect to angiosperm flowers and their pollinators.
Journal Article
Genome-wide identification and expression pattern analysis of auxin response factor (ARF) genes in Chionanthus retusus and functional characterization of CrARF37 in terms of its effect on flower shape
Background
The Auxin Response Factor (
ARF
) gene family is ubiquitous in the plant kingdom, serving as a pivotal gene in the auxin signaling pathway. Members of this gene family encode transcription factors that regulate diverse aspects of plant growth and development. Notably, the Class IIa and Class IIb subfamilies within the ARF gene family play a vital role in plant flower development and morphogenesis.
Chionanthus retusus
, as significant ornamental plants in gardens, exhibit multiple flower forms, and changes in these forms have garnered substantial attention in the selection and cultivation of new varieties.
Result
In this study, we utilized the latest reference genome to conduct a comprehensive identification and analysis of the
ARF
gene in
C. retusus
(2n = 2x = 46), and examined its expression patterns in individuals with varying flower morphologies and generated transgenic
Arabidopsis
overexpressing
CrARF37
and analyzed its function in flower morphogenesis. We identified 49
ARF
genes in
C. retusus
, which can be categorized into four subfamilies and are distributed across 18 chromosomes. Genomic collinearity analysis demonstrated their conservation across evolution, and gene structure, domain, and motif analyses further confirmed their structural conservation. Ultimately, based on expression patterns in individuals exhibiting various flower morphologies, we identified
CrARF32
,
CrARF37
, and
CrARF39
as potential contributors to the formation of
C. retusus
flower morphology. Subsequently, we generated
CrARF37
-overexpressing transgenic
Arabidopsis
, and phenotypic analysis revealed significantly increased length and number of flower veins compared to controls.
Conclusion
Based on gene family analysis, transcriptome gene co-expression network, and transgenic functional validation, we identified three ARF genes that may be associated with differences in
C. retutus
flower morphology. In addition, we validated the transgenic function to elucidate how
CrARF37
affects the development of floral vascular tissue.Our findings will enhance our understanding of flower morphological development and provide valuable theoretical insights for Osmanthus cultivation.
Journal Article