Ancient reticulation, incomplete lineage sorting and the evolution of the pyrenoid at the dawn of hornwort diversification.

Background And Aims: Resolving the phylogeny of hornworts is critical in understanding the evolution of key morphological characters that are unique to the group, including the pyrenoid. Extensive phylogenomic analyses have revealed unexpected complexities in the placement of Leiosporoceros, the previously identified sister taxon to other hornworts. We explore the role of incomplete lineage sorting (ILS) and ancient reticulation in resolving interrelationships and comprehending the diversification and evolutionary processes within hornworts.

Plant biology: Mapping meristem morphogenesis in Marchantia.

The use of state-of-the-art imaging, underpinned by molecular data, for the first time provides a clear understanding of two fundamental processes in liverworts - the establishment of dorsoventrality and origin of apical meristems. This work opens the door to exploring many new facets of plant morphogenesis.

The biology of subsp Bischl. & Boissel. Dub in nature.

Introduction: Though used as the model liverwort in culture for several decades, the biology of Marchantia polymorpha subsp. ruderalis in nature has never been documented in detail in a single account.

Methods: Here we synthesize routine field observations documented with hundreds of images of M.

Evolution of phenotypic disparity in the plant kingdom.

The plant kingdom exhibits diverse bodyplans, from single-celled algae to complex multicellular land plants, but it is unclear how this phenotypic disparity was achieved. Here we show that the living divisions comprise discrete clusters within morphospace, separated largely by reproductive innovations, the extinction of evolutionary intermediates and lineage-specific evolution. Phenotypic complexity correlates not with disparity but with ploidy history, reflecting the role of genome duplication in plant macroevolution.

Carbon for nutrient exchange between Lycopodiella inundata and Mucoromycotina fine root endophytes is unresponsive to high atmospheric CO.

Non-vascular plants associating with arbuscular mycorrhizal (AMF) and Mucoromycotina 'fine root endophyte' (MFRE) fungi derive greater benefits from their fungal associates under higher atmospheric [CO] (a[CO]) than ambient; however, nothing is known about how changes in a[CO] affect MFRE function in vascular plants. We measured movement of phosphorus (P), nitrogen (N) and carbon (C) between the lycophyte Lycopodiella inundata and Mucoromycotina fine root endophyte fungi using P-orthophosphate,  N-ammonium chloride and CO isotope tracers under ambient and elevated a[CO] concentrations of 440 and 800 ppm, respectively. Transfers of P and  N from MFRE to plants were unaffected by changes in a[CO].

Moss stomata do not respond to light and CO concentration but facilitate carbon uptake by sporophytes: a gas exchange, stomatal aperture, and C-labelling study.

Stomata exert control on fluxes of CO and water (H O) in the majority of vascular plants and thus are pivotal for planetary fluxes of carbon and H 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 CO labelling, with supporting data from gravimetry and optical and scanning electron microscopy, were used to measure CO assimilation and water exchange on young, green, ± fully expanded capsules of 11 moss species with a range of stomatal numbers, distributions, and aperture sizes.

The distribution and evolution of fungal symbioses in ancient lineages of land plants.

An accurate understanding of the diversity and distribution of fungal symbioses in land plants is essential for mycorrhizal research. Here we update the seminal work of Wang and Qiu (Mycorrhiza 16:299-363, 2006) with a long-overdue focus on early-diverging land plant lineages, which were considerably under-represented in their survey, by examining the published literature to compile data on the status of fungal symbioses in liverworts, hornworts and lycophytes. Our survey combines data from 84 publications, including recent, post-2006, reports of Mucoromycotina associations in these lineages, to produce a list of at least 591 species with known fungal symbiosis status, 180 of which were included in Wang and Qiu (Mycorrhiza 16:299-363, 2006).

Evolution and networks in ancient and widespread symbioses between Mucoromycotina and liverworts.

Like the majority of land plants, liverworts regularly form intimate symbioses with arbuscular mycorrhizal fungi (Glomeromycotina). Recent phylogenetic and physiological studies report that they also form intimate symbioses with Mucoromycotina fungi and that some of these, like those involving Glomeromycotina, represent nutritional mutualisms. To compare these symbioses, we carried out a global analysis of Mucoromycotina fungi in liverworts and other plants using species delimitation, ancestral reconstruction, and network analyses.

Mucoromycotina Fine Root Endophyte Fungi Form Nutritional Mutualisms with Vascular Plants.

Fungi and plants have engaged in intimate symbioses that are globally widespread and have driven terrestrial biogeochemical processes since plant terrestrialization >500 million years ago. Recently, hitherto unknown nutritional mutualisms involving ancient lineages of fungi and nonvascular plants have been discovered, although their extent and functional significance in vascular plants remain uncertain. Here, we provide evidence of carbon-for-nitrogen exchange between an early-diverging vascular plant () and Mucoromycotina (Endogonales) fine root endophyte fungi.

Functional complementarity of ancient plant-fungal mutualisms: contrasting nitrogen, phosphorus and carbon exchanges between Mucoromycotina and Glomeromycotina fungal symbionts of liverworts.

Liverworts, which are amongst the earliest divergent plant lineages and important ecosystem pioneers, often form nutritional mutualisms with arbuscular mycorrhiza-forming Glomeromycotina and fine-root endophytic Mucoromycotina fungi, both of which coevolved with early land plants. Some liverworts, in common with many later divergent plants, harbour both fungal groups, suggesting these fungi may complementarily improve plant access to different soil nutrients. We tested this hypothesis by growing liverworts in single and dual fungal partnerships under a modern atmosphere and under 1500 ppm [CO ], as experienced by early land plants.

Ancient plants with ancient fungi: liverworts associate with early-diverging arbuscular mycorrhizal fungi.

Arbuscular mycorrhizas are widespread in land plants including liverworts, some of the closest living relatives of the first plants to colonize land 500 million years ago (MYA). Previous investigations reported near-exclusive colonization of liverworts by the most recently evolved arbuscular mycorrhizal fungi, the Glomeraceae, indicating a recent acquisition from flowering plants at odds with the widely held notion that arbuscular mycorrhizal-like associations in liverworts represent the ancestral symbiotic condition in land plants. We performed an analysis of symbiotic fungi in 674 globally collected liverworts using molecular phylogenetics and electron microscopy.

Hornwort stomata do not respond actively to exogenous and environmental cues.

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.

From rhizoids to roots? Experimental evidence of mutualism between liverworts and ascomycete fungi.

Background And Aims: The rhizoids of leafy liverworts (Jungermanniales, Marchantiophyta) are commonly colonized by the ascomycete fungus Pezoloma ericae. These associations are hypothesized to be functionally analogous to the ericoid mycorrhizas (ErMs) formed by P. ericae with the roots of Ericaceae plants in terms of bi-directional phosphorus for carbon exchange; however, this remains unproven.

A mycorrhizal revolution.

It has long been postulated that symbiotic fungi facilitated plant migrations onto land through enhancing the scavenging of mineral nutrients and exchanging these for photosynthetically fixed organic carbon. Today, land plant-fungal symbioses are both widespread and diverse. Recent discoveries show that a variety of potential fungal associates were likely available to the earliest land plants, and that these early partnerships were probably affected by changing atmospheric CO concentrations.

The evolution of the stomatal apparatus: intercellular spaces and sporophyte water relations in bryophytes-two ignored dimensions.

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.

Functional analysis of liverworts in dual symbiosis with Glomeromycota and Mucoromycotina fungi under a simulated Palaeozoic CO2 decline.

Most land plants form mutualistic associations with arbuscular mycorrhizal fungi of the Glomeromycota, but recent studies have found that ancient plant lineages form mutualisms with Mucoromycotina fungi. Simultaneous associations with both fungal lineages have now been found in some plants, necessitating studies to understand the functional and evolutionary significance of these tripartite associations for the first time. We investigate the physiology and cytology of dual fungal symbioses in the early-diverging liverworts Allisonia and Neohodgsonia at modern and Palaeozoic-like elevated atmospheric CO2 concentrations under which they are thought to have evolved.

Symbiotic options for the conquest of land.

The domination of the landmasses of Earth by plants starting during the Ordovician Period drastically altered the development of the biosphere and the composition of the atmosphere, with far-reaching consequences for all life ever since. It is widely thought that symbiotic soil fungi facilitated the colonization of the terrestrial environment by plants. However, recent discoveries in molecular ecology, physiology, cytology, and paleontology have brought into question the hitherto-assumed identity and biology of the fungi engaged in symbiosis with the earliest-diverging lineages of extant land plants.