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Baczyński J, Claßen-Bockhoff R. Pseudanthia in angiosperms: a review. ANNALS OF BOTANY 2023; 132:179-202. [PMID: 37478306 PMCID: PMC10583202 DOI: 10.1093/aob/mcad103] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 07/19/2023] [Indexed: 07/23/2023]
Abstract
BACKGROUND Pseudanthia or 'false flowers' are multiflowered units that resemble solitary flowers in form and function. Over the last century the term 'pseudanthium' has been applied to a wide array of morphologically divergent blossoms, ranging from those with easily noticeable florets to derived, reduced units in which individual flowers become almost indistinguishable. Although initially admired mostly by botanists, the diversity and widespread distribution of pseudanthia across angiosperms has already made them a fascinating topic for evolutionary and developmental comparative studies. SCOPE This review synthesizes historical and current concepts on the biology of pseudanthia. Our first aim is to establish a clear, operational definition of pseudanthium and disentangle common terminological misconceptions surrounding that term. Our second aim is to summarize knowledge of the morphological and developmental diversity of pseudanthia and embed it within a modern phylogenetic framework. Lastly, we want to provide a comprehensive overview on the evolution and ecological importance of pseudanthia and outline perspectives for future studies. CONCLUSIONS The understanding of pseudanthia has changed multiple times and reflects three different interpretations of their 'flower-like' qualities: developmental (similarity in structure), figural (similarity in form and function) and phylogenetic (homology between angiosperm flowers and monoecious reproductive shoots in gymnosperms). Here, we propose to narrow the term pseudanthium to multiflowered blossoms resembling zoophilous flowers in form, i.e. in being structurally subdivided in a showy periphery and a reproductive centre. According to this definition, pseudanthia sensu stricto evolved independently in at least 41 angiosperm families. The recurrent acquisition of pseudanthia sensu stricto in all major lineages of flowering plants indicates repeated interactions between developmental constraints (smallness of flowers, meristematic conditions) and selective pressures, such as demands of pollinators and/or environmental conditions.
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Affiliation(s)
- Jakub Baczyński
- Institute of Evolutionary Biology, Faculty of Biology, Biological and Chemical Research Centre, University of Warsaw, Warsaw, Poland
- Department of Plant Biology, Miller Plant Sciences, University of Georgia, Athens, Georgia, USA
| | - Regine Claßen-Bockhoff
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg-University, Mainz, Germany
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Stephens RE, Gallagher RV, Dun L, Cornwell W, Sauquet H. Insect pollination for most of angiosperm evolutionary history. THE NEW PHYTOLOGIST 2023; 240:880-891. [PMID: 37276503 DOI: 10.1111/nph.18993] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 04/30/2023] [Indexed: 06/07/2023]
Abstract
Most contemporary angiosperms (flowering plants) are insect pollinated, but pollination by wind, water or vertebrates occurs in many lineages. Though evidence suggests insect pollination may be ancestral in angiosperms, this is yet to be assessed across the full phylogeny. Here, we reconstruct the ancestral pollination mode of angiosperms and quantify the timing and environmental associations of pollination shifts. We use a robust, dated phylogeny and species-level sampling across all angiosperm families to model the evolution of pollination modes. Data on the pollination system or syndrome of 1160 species were collated from the primary literature. Angiosperms were ancestrally insect pollinated, and insects have pollinated angiosperms for c. 86% of angiosperm evolutionary history. Wind pollination evolved at least 42 times, with few reversals to animal pollination. Transitions between insect and vertebrate pollination were more frequent: vertebrate pollination evolved at least 39 times from an insect-pollinated ancestor with at least 26 reversals. The probability of wind pollination increases with habitat openness (measured by Leaf Area Index) and distance from the equator. Our reconstruction gives a clear overview of pollination macroevolution across angiosperms, highlighting the long history of interactions between insect pollinators and angiosperms still vital to biodiversity today.
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Affiliation(s)
- Ruby E Stephens
- School of Natural Sciences, Macquarie University, Sydney, NSW, 2109, Australia
- National Herbarium of New South Wales (NSW), Royal Botanic Gardens and Domain Trust, Sydney, NSW, 2000, Australia
| | - Rachael V Gallagher
- School of Natural Sciences, Macquarie University, Sydney, NSW, 2109, Australia
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, 2753, Australia
| | - Lily Dun
- National Herbarium of New South Wales (NSW), Royal Botanic Gardens and Domain Trust, Sydney, NSW, 2000, Australia
- Evolution and Ecology Research Centre, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Will Cornwell
- Evolution and Ecology Research Centre, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Hervé Sauquet
- National Herbarium of New South Wales (NSW), Royal Botanic Gardens and Domain Trust, Sydney, NSW, 2000, Australia
- Evolution and Ecology Research Centre, University of New South Wales, Sydney, NSW, 2052, Australia
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Taylor ML, Giffei BL, Dang CL, Wilden AE, Altrichter KM, Baker EC, Nguyen R, Oki DS. Reproductive ecology and postpollination development in the hydrophilous monocot Ruppia maritima. AMERICAN JOURNAL OF BOTANY 2020; 107:689-699. [PMID: 32170723 DOI: 10.1002/ajb2.1447] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 01/21/2020] [Indexed: 06/10/2023]
Abstract
PREMISE Water-pollination (hydrophily) is a rare but important pollination mechanism that has allowed angiosperms to colonize marine and aquatic habitats. Hydrophilous plants face unique reproductive challenges, and many have evolved characteristic pollen traits and pollination strategies that may have downstream consequences for pollen performance. However, little is known about reproductive development in the life history stage between pollination and fertilization (the progamic phase) in hydrophilous plants. The purpose of this study was to characterize reproductive ecology and postpollination development in water-pollinated Ruppia maritima L. METHODS Naturally pollinated inflorescences of R. maritima were collected from the field. Experimental pollinations using both putatively outcross and self pollen were conducted in the greenhouse and inflorescences were collected at appropriate intervals after pollination. Pollen reception, pollen germination, pollen tube growth, and carpel morphology were characterized. RESULTS Ruppia maritima exhibits incomplete protogyny, allowing for delayed selfing. Pollen germinated within 15 min after pollination. The average shortest possible pollen tube pathway was 425 μm and pollen tubes first reached the ovule at 45 min after pollination. The mean adjusted pollen tube growth rate was 551 μm/h. CONCLUSIONS Ruppia pollen is adapted for rapid pollen germination, which is likely advantageous in an aquatic habitat. Small effective pollen loads suggest that pollen competition intensity is low. Selection for traits such as a long period of stigma receptivity, fast pollen germination, and carpel morphology likely played a larger role in shaping postpollination reproductive development in Ruppia than evolution in pollen tube growth rates.
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Affiliation(s)
- Mackenzie L Taylor
- Department of Biology, Creighton University, Omaha, Nebraska, 68178, USA
| | - Bridget L Giffei
- Department of Biology, Creighton University, Omaha, Nebraska, 68178, USA
| | - Christie L Dang
- Department of Biology, Creighton University, Omaha, Nebraska, 68178, USA
| | - Ana E Wilden
- Department of Biology, Creighton University, Omaha, Nebraska, 68178, USA
| | | | - Emma C Baker
- Department of Biology, Creighton University, Omaha, Nebraska, 68178, USA
| | - Richard Nguyen
- Department of Biology, Creighton University, Omaha, Nebraska, 68178, USA
| | - Dayton S Oki
- Department of Biology, Creighton University, Omaha, Nebraska, 68178, USA
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Abstract
With the origin of pollination in ancient seed plants, the male gametophyte ("pollen") began to evolve a new and unique life history stage, the progamic phase, a post-pollination period in which pollen sexual maturation occurs in interaction with sporophyte-derived tissues. Pollen performance traits mediate the timing of the fertilization process, often in competition with other pollen, via the speed of pollen germination, sperm development, and pollen tube growth. Studies of pollen development rarely address the issue of performance or its evolution, which involves linking variation in developmental rates to relative fitness within populations or to adaptations on a macroevolutionary scale. Modifications to the pollen tube pathway and changes in the intensity of pollen competition affect the direction and strength of selection on pollen performance. Hence, pollen developmental evolution is always contextual-it involves both the population biology of pollen reaching stigmas and the co-evolution of sporophytic traits, such as the pollen tube pathway and mating system. For most species, performance evolution generally reflects a wandering history of periods of directional selection and relaxed selection, channeled by developmental limitations, a pattern that favors the accumulation of diversity and redundancy in developmental mechanisms and the genetic machinery. Developmental biologists are focused on finding universal mechanisms that underlie pollen function, and these are largely mechanisms that have evolved through their effects on performance. Here, we suggest ways in which studies of pollen performance or function could progress by cross-fertilization between the "evo" and "devo" fields.
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Affiliation(s)
- Joseph H Williams
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, United States.
| | - John B Reese
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, United States
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Goodwillie C, Weber JJ. The best of both worlds? A review of delayed selfing in flowering plants. AMERICAN JOURNAL OF BOTANY 2018; 105:641-655. [PMID: 29630718 DOI: 10.1002/ajb2.1045] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2017] [Accepted: 01/17/2018] [Indexed: 05/27/2023]
Abstract
PREMISE OF STUDY In a seminal body of theory, Lloyd showed that the fitness consequences of selfing will depend on its timing in anthesis. Selfing that occurs after opportunities for outcrossing or pollen dispersal can provide reproductive assurance when pollinators are limited and is expected to incur little cost, even when inbreeding depression is high. As a result, delayed selfing is often interpreted as a "best-of-both-worlds" mating system that combines the advantages of selfing and outcrossing. METHODS We surveyed 65 empirical studies of delayed selfing, recording floral mechanisms and examining information on inbreeding depression, autofertility, and other parameters to test the support for delayed selfing as a best-of-both-worlds strategy. KEY RESULTS Phylogenetic distribution of the diverse floral mechanisms suggests that some basic floral structures may predispose plant taxa to evolve delayed selfing. Delayed selfing appears to serve as a best-of-both-worlds strategy in some but not all species. While the capacity for autonomous selfing is often high, it is lower, in some cases, than in related species with earlier modes of selfing. In other delayed-selfers, low inbreeding depression and reduced investment in corollas and pollen suggest limited benefits from outcrossing. CONCLUSIONS Despite a growing literature on the subject, experimental evidence for delayed selfing is limited and major gaps in knowledge remain, particularly with respect to the stability of delayed selfing and the conditions that may favor transitions between delayed and earlier selfing. Finally, we suggest a potential role of delayed selfing in facilitating transitions from self-incompatibility to selfing.
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Affiliation(s)
- Carol Goodwillie
- East Carolina University, Department of Biology, Howell Science Building, Greenville, NC, 27858
| | - Jennifer J Weber
- Southeast Missouri State University, Department of Biology, One University Plaza, MS 6200, Cape Girardeau, MO, 63701
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Marques I, Montgomery SA, Barker MS, Macfarlane TD, Conran JG, Catalán P, Rieseberg LH, Rudall PJ, Graham SW. Transcriptome-derived evidence supports recent polyploidization and a major phylogeographic division in Trithuria submersa (Hydatellaceae, Nymphaeales). THE NEW PHYTOLOGIST 2016; 210:310-323. [PMID: 26612464 DOI: 10.1111/nph.13755] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2015] [Accepted: 10/12/2015] [Indexed: 06/05/2023]
Abstract
Relatively little is known about species-level genetic diversity in flowering plants outside the eudicots and monocots, and it is often unclear how to interpret genetic patterns in lineages with whole-genome duplications. We addressed these issues in a polyploid representative of Hydatellaceae, part of the water-lily order Nymphaeales. We examined a transcriptome of Trithuria submersa for evidence of recent whole-genome duplication, and applied transcriptome-derived microsatellite (expressed-sequence tag simple-sequence repeat (EST-SSR)) primers to survey genetic variation in populations across its range in mainland Australia. A transcriptome-based Ks plot revealed at least one recent polyploidization event, consistent with fixed heterozygous genotypes representing underlying sets of homeologous loci. A strong genetic division coincides with a trans-Nullarbor biogeographic boundary. Patterns of 'allelic' variation (no more than two variants per EST-SSR genotype) and recently published chromosomal evidence are consistent with the predicted polyploidization event and substantial homozygosity underlying fixed heterozygote SSR genotypes, which in turn reflect a selfing mating system. The Nullarbor Plain is a barrier to gene flow between two deep lineages of T. submersa that may represent cryptic species. The markers developed here should also be useful for further disentangling species relationships, and provide a first step towards future genomic studies in Trithuria.
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Affiliation(s)
- Isabel Marques
- Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada
- UBC Botanical Garden & Centre for Plant Research, University of British Columbia, 6804 Marine Drive SW, Vancouver, BC, V6T 1Z4, Canada
- Department of Agricultural and Environmental Sciences, High Polytechnic School of Huesca, University of Zaragoza, C/Carretera de Cuarte Km 1, Huesca, E22071, Spain
| | - Sean A Montgomery
- Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada
- UBC Botanical Garden & Centre for Plant Research, University of British Columbia, 6804 Marine Drive SW, Vancouver, BC, V6T 1Z4, Canada
| | - Michael S Barker
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA
| | - Terry D Macfarlane
- Western Australian Herbarium, Science and Conservation Division, Department of Parks and Wildlife, Locked Bag 104, Bentley Delivery Centre, Bentley, WA, 6983, Australia
| | - John G Conran
- School of Biological Sciences, Australian Centre for Evolutionary Biology and Biodiversity & Sprigg Geobiology Centre, The University of Adelaide, Benham Bldg DX 650 312, Adelaide, SA, 5005, Australia
| | - Pilar Catalán
- Department of Agricultural and Environmental Sciences, High Polytechnic School of Huesca, University of Zaragoza, C/Carretera de Cuarte Km 1, Huesca, E22071, Spain
- Department of Botany, Institute of Biology, Tomsk State University, Lenin Av. 36, Tomsk, 634050, Russia
| | - Loren H Rieseberg
- Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada
| | - Paula J Rudall
- Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK
| | - Sean W Graham
- Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada
- UBC Botanical Garden & Centre for Plant Research, University of British Columbia, 6804 Marine Drive SW, Vancouver, BC, V6T 1Z4, Canada
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Taylor ML, Cooper RL, Schneider EL, Osborn JM. Pollen structure and development in Nymphaeales: insights into character evolution in an ancient angiosperm lineage. AMERICAN JOURNAL OF BOTANY 2015; 102:1685-1702. [PMID: 26419810 DOI: 10.3732/ajb.1500249] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Accepted: 08/25/2015] [Indexed: 06/05/2023]
Abstract
PREMISE OF THE STUDY A knowledge of pollen characters in early-diverging angiosperm lineages is essential for understanding pollen evolution and the role of pollen in angiosperm diversification. In this paper, we report and synthesize data on mature pollen and pollen ontogeny from all genera of Nymphaeales within a comparative, phylogenetic context and consider pollen evolution in this early-diverging angiosperm lineage. We describe mature pollen characters for Euryale, Barclaya, and Nymphaea ondinea, taxa for which little to no structural data exist. METHODS We studied mature pollen for all nymphaealean genera using light, scanning electron, and transmission electron microscopy. We reviewed published reports of nymphaealean pollen to provide a comprehensive discussion of pollen characters in water lilies. KEY RESULTS Nymphaeales exhibit diversity in key pollen characters, including dispersal unit size, ornamentation, aperture morphology, and tapetum type. All Nymphaeales pollen are tectate-columellate, exhibiting one of two distinct patterns of infratectal ultrastructure-a thick infratectal space with robust columellae or a thin infratectal space with thin columellae. All genera have pollen with a lamellate endexine that becomes compressed in the proximal, but not distal wall. This endexine ultrastructure supports the operculate hypothesis for aperture origin. Nymphaeaceae pollen exhibit a membranous granular layer, which is a synapomorphy of the family. CONCLUSIONS Variation in pollen characters indicates that significant potential for lability in pollen development was present in Nymphaeales at the time of its divergence from the rest of angiosperms. Structural and ontogenetic data are essential for interpreting pollen characters, such as infratectum and endexine ultrastructure in Nymphaeales.
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Affiliation(s)
- Mackenzie L Taylor
- Department of Biology, Creighton University, 2500 California Plaza, Omaha, Nebraska 68178-0324 USA
| | - Ranessa L Cooper
- Biology Department, Hillsdale College, 33 East College Street, Hillsdale, Michigan 49242 USA
| | - Edward L Schneider
- The University of Minnesota Landscape Arboretum, 3675 Arboretum Drive, Chaska, Minnesota 55318 USA
| | - Jeffrey M Osborn
- School of Science, The College of New Jersey, P.O. Box 7718, 2000 Pennington Road, Ewing, New Jersey 08628-0718 USA
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Costa M, Pereira AM, Rudall PJ, Coimbra S. Immunolocalization of arabinogalactan proteins (AGPs) in reproductive structures of an early-divergent angiosperm, Trithuria (Hydatellaceae). ANNALS OF BOTANY 2013; 111. [PMID: 23186834 PMCID: PMC3555524 DOI: 10.1093/aob/mcs256] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
BACKGROUND AND AIMS Trithuria is the sole genus of Hydatellaceae, a family of the early-divergent angiosperm lineage Nymphaeales (water-lilies). In this study different arabinogalactan protein (AGP) epitopes in T. submersa were evaluated in order to understand the diversity of these proteins and their functions in flowering plants. METHODS Immunolabelling of different AGPs and pectin epitopes in reproductive structures of T. submersa at the stage of early seed development was achieved by immunofluorescence of specific antibodies. KEY RESULTS AGPs in Trithuria pistil tissues could be important as structural proteins and also as possible signalling molecules. Intense labelling was obtained with anti-AGP antibodies both in the anthers and in the intine wall, the latter associated with pollen tube emergence. CONCLUSIONS AGPs could play a significant role in Trithuria reproduction, due to their specific presence in the pollen tube pathway. The results agree with labellings obtained for Arabidopsis and confirms the importance of AGPs in angiosperm reproductive structures as essential structural components and probably important signalling molecules.
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Affiliation(s)
- Mário Costa
- Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Edifício FC4 Rua do Campo Alegre 4169-007 Porto, Portugal
- BioFIG, Center for Biodiversity, Functional and Integrative Genomics, Portugal
| | - Ana Marta Pereira
- Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Edifício FC4 Rua do Campo Alegre 4169-007 Porto, Portugal
- BioFIG, Center for Biodiversity, Functional and Integrative Genomics, Portugal
| | - Paula J. Rudall
- Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AAB, UK
| | - Sílvia Coimbra
- Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Edifício FC4 Rua do Campo Alegre 4169-007 Porto, Portugal
- BioFIG, Center for Biodiversity, Functional and Integrative Genomics, Portugal
- For correspondence. E-mail
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Williams JH. Pollen Tube Growth Rates and the Diversification of Flowering Plant Reproductive Cycles. INTERNATIONAL JOURNAL OF PLANT SCIENCES 2012. [PMID: 0 DOI: 10.1086/665822] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
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Friedman WE, Bachelier JB, Hormaza JI. Embryology in Trithuria submersa (Hydatellaceae) and relationships between embryo, endosperm, and perisperm in early-diverging flowering plants. AMERICAN JOURNAL OF BOTANY 2012; 99:1083-95. [PMID: 22688427 DOI: 10.3732/ajb.1200066] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
PREMISE OF THE STUDY Despite their highly reduced morphology, Hydatellaceae bear the unmistakable embryological signature of Nymphaeales, including a starch-rich maternal perisperm and a minute biparental endosperm and embryo. The co-occurrence of perisperm and endosperm in Nymphaeales and other lineages of flowering plants, and their respective functions during the course of seed development and embryo germination, remain enigmatic. METHODS Development of the embryo, endosperm, and perisperm was examined histologically from fertilization through germination in flowers and fruits of Trithuria submersa. KEY RESULTS The embryo of T. submersa initiates two cotyledons prior to seed maturity/dormancy, and their tips remain in contact with the endosperm throughout germination. The endosperm persists as a single layer of cells and serves as the interface between the embryo and the perisperm. The perisperm contains carbohydrates and proteins, and functions as the main storage tissue. The endosperm accumulates proteins and aleurone grains and functions as a transfer cell layer. CONCLUSIONS In Nymphaeales, the multiple roles of a more typical endosperm have been separated into two different tissues and genetic entities: a maternal perisperm (nutrient acquisition, storage, mobilization) and a minute biparental endosperm (nutrient transfer to the embryo). The presence of perisperms among several other ancient lineages of angiosperms suggests a modest degree of developmental and functional lability for the nutrient storage tissue (perisperm or endosperm) within seeds during the early evolution of flowering plants. Finally, we examine the evolutionary developmental hypothesis that, contrary to longstanding assumptions, an embryo-nourishing perisperm along with a minute endosperm may represent the plesiomorphic condition for flowering plants.
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Affiliation(s)
- William E Friedman
- Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, Massachusetts 02138 USA.
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Iles WJD, Rudall PJ, Sokoloff DD, Remizowa MV, Macfarlane TD, Logacheva MD, Graham SW. Molecular phylogenetics of Hydatellaceae (Nymphaeales): sexual-system homoplasy and a new sectional classification. AMERICAN JOURNAL OF BOTANY 2012; 99:663-676. [PMID: 22473977 DOI: 10.3732/ajb.1100524] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
PREMISE OF THE STUDY Species relationships are unknown in Hydatellaceae, a small family of dwarf aquatics related to water lilies that arose near the base of angiosperm phylogeny. Here we use molecular evidence to infer a species tree for the family and apply this to reconstructing major transitions in morphology and sexual system in this early branch of angiosperms. METHODS We assembled plastid (atpB, matK, ndhF, rbcL) and nuclear (ribosomal ITS) data for 50 samples (including outgroups) and estimated a species tree for Hydatellaceae using a Bayesian multispecies coalescent approach. We reconstructed the evolution of several morphological characters, then tested for associations between sexual system and reproductive morphology using phylogenetic ANOVA. KEY RESULTS Dioecious species of Hydatellaceae have significantly greater stamen number and anther length than do cosexual species, suggesting changes in male function. The perennial habit that defines one subclade likely represents a reversion from annuality. Species relationships do not fall along traditional morphological divisions, but new sections proposed here are supported by fruit and seed synapomorphies. The earliest split in the family is reflected in geography and climate (i.e., tropical vs. subtropical/temperate clades). We found limited evidence of incongruence between plastid and nuclear trees, with one exception involving gene-tree nonmonophyly for two close relatives (Trithuria submersa, T. bibracteata). CONCLUSIONS While the direction of sexual-system evolution is ambiguous, transitions are significantly associated with changes in involucral phyllome length and proxies of pollen production. We propose a new sectional circumscription based on fruit, seed, and DNA evidence.
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Affiliation(s)
- William J D Iles
- UBC Botanical Garden & Centre for Plant Research, and Department of Botany, 6270 University Boulevard, University of British Columbia, Vancouver, BC, Canada.
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Taylor ML, Williams JH. Pollen tube development in two species of Trithuria (Hydatellaceae) with contrasting breeding systems. ACTA ACUST UNITED AC 2012; 25:83-96. [DOI: 10.1007/s00497-012-0183-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Accepted: 02/08/2012] [Indexed: 11/30/2022]
Affiliation(s)
- Mackenzie L Taylor
- Department of Biology, Creighton University, 2500 California Plaza, Omaha, NE 68178, USA.
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13
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Prychid CJ, Sokoloff DD, Remizowa MV, Tuckett RE, Yadav SR, Rudall PJ. Unique stigmatic hairs and pollen-tube growth within the stigmatic cell wall in the early-divergent angiosperm family Hydatellaceae. ANNALS OF BOTANY 2011; 108:599-608. [PMID: 21320877 PMCID: PMC3170147 DOI: 10.1093/aob/mcr021] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Accepted: 01/05/2011] [Indexed: 05/07/2023]
Abstract
BACKGROUND AND AIMS The ultrastructure of the pollen tubes and the unusual multicellular stigmatic hairs of Trithuria, the sole genus of Hydatellaceae, are described in the context of comparative studies of stigmatic and transmitting tissue in other early-divergent angiosperms. METHODS Scanning and transmission electron microscopy and immunocytochemistry are used to study the structure and composition of both mature and immature stigmatic hair cells and pollen-tube growth in Trithuria. KEY RESULTS Trithuria possesses a dry-type stigma. Pollen tubes grow within the cell walls of the long multicellular stigmatic hairs. Immunocytochemistry results suggest that arabinogalactan proteins are involved in attracting the pollen tubes through the stigmatic cuticle. Most tubes grow along the hair axis towards its base, but some grow towards the hair apex, suggesting that pollen tubes are guided by both physical constraints such as microfibril orientation and the presence of binding factors such as unesterified pectins and adhesive proteins. CONCLUSIONS The presence of a dry-type stigma in Trithuria supports the hypothesis that this condition is ancestral in angiosperms. Each multicellular stigmatic hair of Hydatellaceae is morphologically homologous with a stigmatic papilla of other angiosperms, but functions as an independent stigma and style. This unusual combination of factors makes Hydatellaceae a useful model for comparative studies of pollen-tube growth in early angiosperms.
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Affiliation(s)
| | - Dmitry D. Sokoloff
- Department of Higher Plants, Biological Faculty, Moscow State University, 119991 Moscow, Russia
| | - Margarita V. Remizowa
- Department of Higher Plants, Biological Faculty, Moscow State University, 119991 Moscow, Russia
| | - Renee E. Tuckett
- University of Western Australia, Crawley, WA 6009 and Botanic Gardens and Parks Authority, Fraser Avenue, West Perth, WA 6005, Australia
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