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Fortin JP, Friedman WE. A stomate by any other name? The open question of hornwort gametophytic pores, their homology, and implications for the evolution of stomates. THE NEW PHYTOLOGIST 2024. [PMID: 39256934 DOI: 10.1111/nph.20094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2024] [Accepted: 08/14/2024] [Indexed: 09/12/2024]
Abstract
Advances in bryophyte genomics and the phylogenetic recovery of hornworts, mosses, and liverworts as a clade have spurred considerable recent interest in character evolution among early embryophytes. Discussion of stomatal evolution, however, has been incomplete; the result of the neglect of certain potential stomate homologues, namely the two-celled epidermal gametophytic pores of hornworts (typically referred to as 'mucilage clefts'). Confusion over the potential homology of these structures is the consequence of a relatively recent consensus that hornwort gametophytic pores ('HGPs' - our term) are not homologous to stomates. We explore the occurrence and diverse functions of stomates throughout the evolutionary history and diversity of extinct and extant embryophytes. We then address arguments for and against homology between known sporophyte- and gametophyte-borne stomates and HGPs and conclude that there is little to no evidence that contradicts the hypothesis of homology. We propose that 'intergenerational heterotopy' might well account for the novel expression of stomates in gametophytes of hornworts, if stomates first evolved in the sporophyte generation of embryophytes. We then explore phylogenetically based hypotheses for the evolution of stomates in both the gametophyte and sporophyte generations of early lineages of embryophytes.
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Affiliation(s)
- James Paul Fortin
- The Arnold Arboretum of Harvard University, 1300 Centre Street, Boston, MA, 02131, USA
| | - William E Friedman
- The Arnold Arboretum of Harvard University, 1300 Centre Street, Boston, MA, 02131, USA
- Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
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Kubásek J, Hájek T, Duckett J, Pressel S, Šantrůček J. Moss stomata do not respond to light and CO 2 concentration but facilitate carbon uptake by sporophytes: a gas exchange, stomatal aperture, and 13 C-labelling study. THE NEW PHYTOLOGIST 2021; 230:1815-1828. [PMID: 33458818 DOI: 10.1111/nph.17208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 01/07/2021] [Indexed: 05/06/2023]
Abstract
Stomata exert control on fluxes of CO2 and water (H2 O) in the majority of vascular plants and thus are pivotal for planetary fluxes of carbon and H2 O. However, in mosses, the significance and possible function of the sporophytic stomata are not well understood, hindering understanding of the ancestral function and evolution of these key structures of land plants. Infrared gas analysis and 13 CO2 labelling, with supporting data from gravimetry and optical and scanning electron microscopy, were used to measure CO2 assimilation and water exchange on young, green, ± fully expanded capsules of 11 moss species with a range of stomatal numbers, distributions, and aperture sizes. Moss sporophytes are effectively homoiohydric. In line with their open fixed apertures, moss stomata, contrary to those in tracheophytes, do not respond to light and CO2 concentration. Whereas the sporophyte cuticle is highly impermeable to gases, stomata are the predominant sites of 13 CO2 entry and H2 O loss in moss sporophytes, and CO2 assimilation is closely linked to total stomatal surface areas. Higher photosynthetic autonomy of moss sporophytes, consequent on the presence of numerous stomata, may have been the key to our understanding of evolution of large, gametophyte-independent sporophytes at the onset of plant terrestrialization.
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Affiliation(s)
- Jiří Kubásek
- Department of Experimental Plant Biology, Faculty of Science, University of South Bohemia, Branišovská, České Budějovice, 1760/31, Czech Republic
| | - Tomáš Hájek
- Department of Experimental Plant Biology, Faculty of Science, University of South Bohemia, Branišovská, České Budějovice, 1760/31, Czech Republic
| | - Jeffrey Duckett
- Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
| | - Silvia Pressel
- Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
| | - Jiří Šantrůček
- Department of Experimental Plant Biology, Faculty of Science, University of South Bohemia, Branišovská, České Budějovice, 1760/31, Czech Republic
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McAdam SAM, Duckett JG, Sussmilch FC, Pressel S, Renzaglia KS, Hedrich R, Brodribb TJ, Merced A. Stomata: the holey grail of plant evolution. AMERICAN JOURNAL OF BOTANY 2021; 108:366-371. [PMID: 33687736 PMCID: PMC8175006 DOI: 10.1002/ajb2.1619] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 09/10/2020] [Indexed: 05/11/2023]
Affiliation(s)
- Scott A M McAdam
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, 47907, USA
| | - Jeffrey G Duckett
- Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
| | - Frances C Sussmilch
- School of Natural Sciences, University of Tasmania, Hobart, TAS, 7001, Australia
| | - Silvia Pressel
- Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
| | - Karen S Renzaglia
- Department of Plant Biology, Southern Illinois University, Carbondale, IL, 62901, USA
| | - Rainer Hedrich
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Würzburg, D-97082, Germany
| | - Timothy J Brodribb
- School of Natural Sciences, University of Tasmania, Hobart, TAS, 7001, Australia
| | - Amelia Merced
- USDA Forest Service, International Institute of Tropical Forestry, San Juan, PR, 00926, USA
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McAdam SAM, Sussmilch FC. The evolving role of abscisic acid in cell function and plant development over geological time. Semin Cell Dev Biol 2020; 109:39-45. [PMID: 32571626 DOI: 10.1016/j.semcdb.2020.06.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 06/10/2020] [Accepted: 06/11/2020] [Indexed: 01/03/2023]
Abstract
Abscisic acid (ABA) is found in a wide diversity of organisms, yet we know most about the hormonal action of this compound in the ecologically dominant and economically important angiosperms. In angiosperms, ABA regulates a suite of critical responses from desiccation tolerance through to seed dormancy and stomatal closure. Work exploring the function of key genes in the ABA signalling pathway of angiosperms has revealed that this signal transduction pathway is ancient, yet considerable change in the physiological roles of this hormone have occurred over geological time. With recent advances in our capacity to characterise gene function in non-angiosperms we are on the cusp of revealing the origins of this critical hormonal signalling pathway in plants, and understanding how a simple hormone may have shaped land plant diversity, ecology and adaptation over the past 500 million years.
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Affiliation(s)
- Scott A M McAdam
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, 47907, USA.
| | - Frances C Sussmilch
- School of Natural Sciences, University of Tasmania, Sandy Bay, TAS, 7005, Australia
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Brodribb TJ, Sussmilch F, McAdam SAM. From reproduction to production, stomata are the master regulators. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 101:756-767. [PMID: 31596990 DOI: 10.1111/tpj.14561] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 09/14/2019] [Accepted: 10/03/2019] [Indexed: 05/22/2023]
Abstract
The best predictor of leaf level photosynthetic rate is the porosity of the leaf surface, as determined by the number and aperture of stomata on the leaf. This remarkable correlation between stomatal porosity (or diffusive conductance to water vapour gs ) and CO2 assimilation rate (A) applies to all major lineages of vascular plants (Figure 1) and is sufficiently predictable that it provides the basis for the model most widely used to predict water and CO2 fluxes from leaves and canopies. Yet the Ball-Berry formulation is only a phenomenological approximation that captures the emergent character of stomatal behaviour. Progressing to a more mechanistic prediction of plant gas exchange is challenging because of the diversity of biological components regulating stomatal action. These processes are the product of more than 400 million years of co-evolution between stomatal, vascular and photosynthetic tissues. Both molecular and structural components link the abiotic world of the whole plant with the turgor pressure of the epidermis and guard cells, which ultimately determine stomatal pore size and porosity to water and CO2 exchange (New Phytol., 168, 2005, 275). In this review we seek to simplify stomatal behaviour by using an evolutionary perspective to understand the principal selective pressures involved in stomatal evolution, thus identifying the primary regulators of stomatal aperture. We start by considering the adaptive process that has locked together the regulation of water and carbon fluxes in vascular plants, finally examining specific evidence for evolution in the proteins responsible for regulating guard cell turgor.
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Affiliation(s)
- Timothy J Brodribb
- School of Natural Sciences, University of Tasmania, Hobart, Tasmania, 7001, Australia
| | - Frances Sussmilch
- Institute for Molecular Plant Physiology and Biophysics, University of Wurzburg, Wuerzburg, Bavaria, Germany
| | - Scott A M McAdam
- Purdue Center for Plant Biology, Purdue University, West Lafayette, IN, USA
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Renzaglia KS, Browning WB, Merced A. With Over 60 Independent Losses, Stomata Are Expendable in Mosses. FRONTIERS IN PLANT SCIENCE 2020; 11:567. [PMID: 32547571 PMCID: PMC7270291 DOI: 10.3389/fpls.2020.00567] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 04/16/2020] [Indexed: 05/22/2023]
Abstract
Because stomata in bryophytes are uniquely located on sporangia, the physiological and evolutionary constraints placed on bryophyte stomata are fundamentally different from those on leaves of tracheophytes. Although losses of stomata have been documented in mosses, the extent to which this evolutionary process occurred remains relatively unexplored. We initiated this study by plotting the known occurrences of stomata loss and numbers per capsule on the most recent moss phylogeny. From this, we identified 40 families and 74 genera that lack stomata, of which at least 63 are independent losses. No trends in stomata losses or numbers are evident in any direction across moss diversity. Extant taxa in early divergent moss lineages either lack stomata or produce pseudostomata that do not form pores. The earliest land plant macrofossils from 400 ma exhibit similar sporangial morphologies and stomatal distribution to extant mosses, suggesting that the earliest mosses may have possessed and lost stomata as is common in the group. To understand why stomata are expendable in mosses, we conducted comparative anatomical studies on a range of mosses with and without stomata. We compared the anatomy of stomate and astomate taxa and the development of intercellular spaces, including substomatal cavities, across mosses. Two types of intercellular spaces that develop differently are seen in peristomate mosses, those associated with stomata and those that surround the spore sac. Capsule architecture in astomate mosses ranges from solid in the taxa in early divergent lineages to containing an internal space that is directly connected to the conducing tissue and is involved in capsule expansion and the nourishment, hydration and development of spores. This anatomy reveals there are different architectural arrangements of tissues within moss capsules that are equally effective in accomplishing the essential processes of sporogenesis and spore dispersal. Stomata are not foundational to these processes.
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Affiliation(s)
- Karen S. Renzaglia
- Plant Biology Department, Southern Illinois University, Carbondale, IL, United States
- *Correspondence: Karen S. Renzaglia,
| | - William B. Browning
- Plant Biology Department, Southern Illinois University, Carbondale, IL, United States
| | - Amelia Merced
- International Institute of Tropical Forestry, USDA Forest Service, San Juan, PR, United States
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Sussmilch FC, Roelfsema MRG, Hedrich R. On the origins of osmotically driven stomatal movements. THE NEW PHYTOLOGIST 2019; 222:84-90. [PMID: 30444541 DOI: 10.1111/nph.15593] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 10/26/2018] [Indexed: 06/09/2023]
Abstract
Contents Summary 84 I. Introduction 84 II. Stomatal form and biomechanics 85 III. Stomatal function 86 IV. Evolution of guard cell ion channels 87 V. Conclusions 88 Acknowledgements 88 Author contributions 88 References 88 SUMMARY: Stomatal pores with apertures that can be adjusted by changes in guard cell turgor have facilitated plant success in dry environments. We explore their evolutionary origins, considering recent findings from bryophytes. Unlike vascular plant stomata, which close to prevent water loss, bryophyte stomata become locked open to promote spore desiccation. We find that the families of ion channels, known to control stomatal movements in angiosperms, are ancient and represented across extant land plants. However, although angiosperm guard cells express specific ion channel genes, none appear specifically expressed in stomata-bearing moss tissues. Given the evolutionary shift in stomatal function from promotion to prevention of water loss, we postulate that ion channels adopted guard cell-specific functions after the divergence of bryophytes.
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Affiliation(s)
- Frances C Sussmilch
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, D-97082, Würzburg, Germany
| | - M Rob G Roelfsema
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, D-97082, Würzburg, Germany
| | - Rainer Hedrich
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, D-97082, Würzburg, Germany
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Merced A, Renzaglia KS. Contrasting pectin polymers in guard cell walls of Arabidopsis and the hornwort Phaeoceros reflect physiological differences. ANNALS OF BOTANY 2019; 123:579-585. [PMID: 30202908 PMCID: PMC6417473 DOI: 10.1093/aob/mcy168] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Revised: 07/17/2018] [Accepted: 08/27/2018] [Indexed: 05/25/2023]
Abstract
BACKGROUND AND AIMS In seed plants, stomata regulate CO2 acquisition and water relations via transpiration, while minimizing water loss. Walls of guard cells are strong yet flexible because they open and close the pore by changing shape over the substomatal cavity. Pectins are necessary for wall flexibility and proper stomata functioning. This study investigates the differences in pectin composition in guard cells of two taxa that represent key lineages of plants with stomata: Arabidopsis, an angiosperm with diurnal stomatal activity, and Phaeoceros, a bryophyte that lacks active stomatal movement. METHODS Using immunolocalization techniques in transmission electron microscopy, this study describes and compares the localization of pectin molecule epitopes essential to stomata function in guard cell walls of Arabidopsis and Phaeoceros. KEY RESULTS In Arabidopsis, unesterified homogalacturonans very strongly localize throughout guard cell walls and are interspersed with arabinan pectins, while methyl-esterified homogalacturonans are restricted to the exterior of the wall, the ledges and the junction with adjacent epidermal cells. In contrast, arabinans are absent in Phaeoceros, and both unesterified and methyl-esterified homogalacturonans localize throughout guard cell walls. CONCLUSIONS Arabinans and unesterified homogalacturonans are required for wall flexibility, which is consistent with active regulation of pore opening in Arabidopsis stomata. In contrast, the lack of arabinans and high levels of methyl-esterified homogalacturonans in guard cell walls of Phaeoceros are congruent with the inability of hornwort stomata to open and close with environmental change. Comparisons across groups demonstrate that variations in guard cell wall composition reflect different physiological activity of stomata in land plants.
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Affiliation(s)
- Amelia Merced
- Institute of Neurobiology, University of Puerto Rico, San Juan, PR, Puerto Rico
| | - Karen S Renzaglia
- Department of Plant Biology, Southern Illinois University, Carbondale, IL, USA
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9
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Rui Y, Chen Y, Kandemir B, Yi H, Wang JZ, Puri VM, Anderson CT. Balancing Strength and Flexibility: How the Synthesis, Organization, and Modification of Guard Cell Walls Govern Stomatal Development and Dynamics. FRONTIERS IN PLANT SCIENCE 2018; 9:1202. [PMID: 30177940 PMCID: PMC6110162 DOI: 10.3389/fpls.2018.01202] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 07/26/2018] [Indexed: 05/02/2023]
Abstract
Guard cells are pairs of epidermal cells that control gas diffusion by regulating the opening and closure of stomatal pores. Guard cells, like other types of plant cells, are surrounded by a three-dimensional, extracellular network of polysaccharide-based wall polymers. In contrast to the walls of diffusely growing cells, guard cell walls have been hypothesized to be uniquely strong and elastic to meet the functional requirements of withstanding high turgor and allowing for reversible stomatal movements. Although the walls of guard cells were long underexplored as compared to extensive studies of stomatal development and guard cell signaling, recent research has provided new genetic, cytological, and physiological data demonstrating that guard cell walls function centrally in stomatal development and dynamics. In this review, we highlight and discuss the latest evidence for how wall polysaccharides are synthesized, deposited, reorganized, modified, and degraded in guard cells, and how these processes influence stomatal form and function. We also raise open questions and provide a perspective on experimental approaches that could be used in the future to shed light on the composition and architecture of guard cell walls.
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Affiliation(s)
- Yue Rui
- Department of Biology, The Pennsylvania State University, University Park, PA, United States
- Intercollege Graduate Degree Program in Plant Biology, The Pennsylvania State University, University Park, PA, United States
| | - Yintong Chen
- Department of Biology, The Pennsylvania State University, University Park, PA, United States
- Intercollege Graduate Degree Program in Molecular Cellular and Integrative Biosciences, The Pennsylvania State University, University Park, PA, United States
| | - Baris Kandemir
- College of Information Sciences and Technology, The Pennsylvania State University, University Park, PA, United States
| | - Hojae Yi
- Department of Agricultural and Biological Engineering, The Pennsylvania State University, University Park, PA, United States
| | - James Z. Wang
- College of Information Sciences and Technology, The Pennsylvania State University, University Park, PA, United States
| | - Virendra M. Puri
- Department of Agricultural and Biological Engineering, The Pennsylvania State University, University Park, PA, United States
| | - Charles T. Anderson
- Department of Biology, The Pennsylvania State University, University Park, PA, United States
- Intercollege Graduate Degree Program in Plant Biology, The Pennsylvania State University, University Park, PA, United States
- Intercollege Graduate Degree Program in Molecular Cellular and Integrative Biosciences, The Pennsylvania State University, University Park, PA, United States
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10
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Pressel S, Renzaglia KS, Dicky Clymo RS, Duckett JG. Hornwort stomata do not respond actively to exogenous and environmental cues. ANNALS OF BOTANY 2018; 122:45-57. [PMID: 29897395 PMCID: PMC6025193 DOI: 10.1093/aob/mcy045] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 03/14/2018] [Indexed: 05/22/2023]
Abstract
Backgrounds and Aims Because stomata in bryophytes occur on sporangia, they are subject to different developmental and evolutionary constraints from those on leaves of tracheophytes. No conclusive experimental evidence exists on the responses of hornwort stomata to exogenous stimulation. Methods Responses of hornwort stomata to abscisic acid (ABA), desiccation, darkness and plasmolysis were compared with those in tracheophyte leaves. Potassium ion concentrations in the guard cells and adjacent cells were analysed by X-ray microanalysis, and the ontogeny of the sporophytic intercellular spaces was compared with those of tracheophytes by cryo-scanning electron microscopy. Key Results The apertures in hornwort stomata open early in development and thereafter remain open. In hornworts, the experimental treatments, based on measurements of >9000 stomata, produced only a slight reduction in aperture dimensions after desiccation and plasmolysis, and no changes following ABA treatments and darkness. In tracheophytes, all these treatments resulted in complete stomatal closure. Potassium concentrations are similar in hornwort guard cells and epidermal cells under all treatments at all times. The small changes in hornwort stomatal dimensions in response to desiccation and plasmolysis are probably mechanical and/or stress responses of all the epidermal and spongy chlorophyllose cells, affecting the guard cells. In contrast to their nascent gas-filled counterparts across tracheophytes, sporophytic intercellular spaces in hornworts are initially liquid filled. Conclusions Our experiments demonstrate a lack of physiological regulation of opening and closing of stomata in hornworts compared with tracheophytes, and support accumulating developmental and structural evidence that stomata in hornworts are primarily involved in sporophyte desiccation and spore discharge rather than the regulation of photosynthesis-related gaseous exchange. Our results run counter to the notion of the early acquisition of active control of stomatal movements in bryophytes as proposed from previous experiments on mosses.
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Affiliation(s)
- Silvia Pressel
- Life Sciences Department, Natural History Museum, London, UK
| | - Karen S Renzaglia
- Plant Biology Department, Southern Illinois University, Carbondale, USA
| | - Richard S Dicky Clymo
- School of Biological and Chemical Sciences, Queen Mary University of London, London, UK
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Duckett JG, Pressel S. The evolution of the stomatal apparatus: intercellular spaces and sporophyte water relations in bryophytes-two ignored dimensions. Philos Trans R Soc Lond B Biol Sci 2018; 373:20160498. [PMID: 29254963 PMCID: PMC5745334 DOI: 10.1098/rstb.2016.0498] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/26/2017] [Indexed: 11/12/2022] Open
Abstract
Cryo-scanning electron microscopy shows that nascent intercellular spaces (ICSs) in bryophytes are liquid-filled, whereas these are gas-filled from the outset in tracheophytes except in the gametophytes of Lycopodiales. ICSs are absent in moss gametophytes and remain liquid-filled in hornwort gametophytes and in both generations in liverworts. Liquid is replaced by gas following stomatal opening in hornworts and is ubiquitous in moss sporophytes even in astomate taxa. New data on moss water relations and sporophyte weights indicate that the latter are homiohydric while X-ray microanalysis reveals an absence of potassium pumps in the stomatal apparatus. The distribution of ICSs in bryophytes is strongly indicative of very ancient multiple origins. Inherent in this scenario is either the dual or triple evolution of stomata. The absence, in mosses, of any relationship between increases in sporophyte biomass and stomata numbers and absences, suggests that CO2 entry through the stomata, possible only after fluid replacement by gas in the ICSs, makes but a minor contribution to sporophyte nutrition. Save for a single claim of active regulation of aperture dimensions in mosses, all other functional and structural data point to the sporophyte desiccation, leading to spore discharge, as the primeval role of the stomatal apparatus.This article is part of a discussion meeting issue 'The Rhynie cherts: our earliest terrestrial ecosystem revisited'.
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Affiliation(s)
- Jeffrey G Duckett
- Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
| | - Silvia Pressel
- Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
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12
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Sussmilch FC, Brodribb TJ, McAdam SAM. What are the evolutionary origins of stomatal responses to abscisic acid in land plants? JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2017; 59:240-260. [PMID: 28093875 DOI: 10.1111/jipb.12523] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Accepted: 01/15/2017] [Indexed: 05/20/2023]
Abstract
The evolution of active stomatal closure in response to leaf water deficit, mediated by the hormone abscisic acid (ABA), has been the subject of recent debate. Two different models for the timing of the evolution of this response recur in the literature. A single-step model for stomatal control suggests that stomata evolved active, ABA-mediated control of stomatal aperture, when these structures first appeared, prior to the divergence of bryophyte and vascular plant lineages. In contrast, a gradualistic model for stomatal control proposes that the most basal vascular plant stomata responded passively to changes in leaf water status. This model suggests that active ABA-driven mechanisms for stomatal responses to water status instead evolved after the divergence of seed plants, culminating in the complex, ABA-mediated responses observed in modern angiosperms. Here we review the findings that form the basis for these two models, including recent work that provides critical molecular insights into resolving this intriguing debate, and find strong evidence to support a gradualistic model for stomatal evolution.
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Affiliation(s)
- Frances C Sussmilch
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
| | - Timothy J Brodribb
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
| | - Scott A M McAdam
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
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Shtein I, Shelef Y, Marom Z, Zelinger E, Schwartz A, Popper ZA, Bar-On B, Harpaz-Saad S. Stomatal cell wall composition: distinctive structural patterns associated with different phylogenetic groups. ANNALS OF BOTANY 2017; 119:1021-1033. [PMID: 28158449 PMCID: PMC5604698 DOI: 10.1093/aob/mcw275] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 12/05/2016] [Indexed: 05/18/2023]
Abstract
Background and Aims Stomatal morphology and function have remained largely conserved throughout ∼400 million years of plant evolution. However, plant cell wall composition has evolved and changed. Here stomatal cell wall composition was investigated in different vascular plant groups in attempt to understand their possible effect on stomatal function. Methods A renewed look at stomatal cell walls was attempted utilizing digitalized polar microscopy, confocal microscopy, histology and a numerical finite-elements simulation. The six species of vascular plants chosen for this study cover a broad structural, ecophysiological and evolutionary spectrum: ferns ( Asplenium nidus and Platycerium bifurcatum ) and angiosperms ( Arabidopsis thaliana and Commelina erecta ) with kidney-shaped stomata, and grasses (angiosperms, family Poaceae) with dumbbell-shaped stomata ( Sorghum bicolor and Triticum aestivum ). Key Results Three distinct patterns of cellulose crystallinity in stomatal cell walls were observed: Type I (kidney-shaped stomata, ferns), Type II (kidney-shaped stomata, angiosperms) and Type III (dumbbell-shaped stomata, grasses). The different stomatal cell wall attributes investigated (cellulose crystallinity, pectins, lignin, phenolics) exhibited taxon-specific patterns, with reciprocal substitution of structural elements in the end-walls of kidney-shaped stomata. According to a numerical bio-mechanical model, the end walls of kidney-shaped stomata develop the highest stresses during opening. Conclusions The data presented demonstrate for the first time the existence of distinct spatial patterns of varying cellulose crystallinity in guard cell walls. It is also highly intriguing that in angiosperms crystalline cellulose appears to have replaced lignin that occurs in the stomatal end-walls of ferns serving a similar wall strengthening function. Such taxon-specific spatial patterns of cell wall components could imply different biomechanical functions, which in turn could be a consequence of differences in environmental selection along the course of plant evolution.
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Affiliation(s)
- Ilana Shtein
- The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot 7610001, Israel
| | - Yaniv Shelef
- Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Ziv Marom
- Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Einat Zelinger
- The Interdepartmental Equipment Unit, The Robert H. Smith Faculty of Agriculture, Food & Environment, The Hebrew University of Jerusalem, Rehovot 7610001, Israel
| | - Amnon Schwartz
- The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot 7610001, Israel
| | - Zoë A. Popper
- Botany and Plant Science, Ryan Institute for Environmental, Marine and Energy Research, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Benny Bar-On
- Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Smadar Harpaz-Saad
- The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot 7610001, Israel
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