Complex wound response mechanisms and phellogen evolution - insights from Early Devonian euphyllophytes.

We analyze the oldest fossil occurrences of wound-response periderm to characterize the development of wound responses in early tracheophytes. The origin of periderm production by a cambium (phellogen), an innovation with key roles in protection of inner plant tissues, is poorly explored; understanding periderm development in early tracheophytes can illuminate key aspects of this process. Anatomy of wound-response tissues is characterized in serial sections in a new Early Devonian (Emsian; c. 400 Ma) euphyllophyte from Quebec (Canada) - Nebuloxyla mikmaqiana sp. nov. - and compared to previously described euphyllophyte periderm from the same fossil locality to reconstruct periderm development. Characterizing development in these oldest periderm occurrences allows us to propose a model for the development of wound-response periderm in early tracheophytes: by phellogen activity that is poorly coordinated laterally but bifacial, producing secondary tissues initially outwardly and subsequently inwardly. The earliest occurrences of wound periderm pre-date the oldest known periderm produced systemically as a regular ontogenetic stage (canonical periderm), suggesting that periderm evolved initially as a wound-response mechanism. We hypothesize that canonical periderm evolved by exaptation of this wound sealing mechanism, whose deployment was triggered by tangential tensional stresses induced in the superficial tissues by vascular cambial growth from within.

Did trees grow up to the light, up to the wind, or down to the water? How modern high productivity colors perception of early plant evolution.

Contents I. II. III. IV. V. Acknowledgements References SUMMARY: Flowering plants can be far more productive than other living land plants. Evidence is reviewed that productivity would have been uniformly lower and less CO2 -responsive before angiosperm evolution, particularly during the early evolution of vascular plants and forests in the Devonian and Carboniferous. This introduces important challenges because paleoecological interpretations have been rooted in understanding of modern angiosperm-dominated ecosystems. One key example is tree evolution: although often thought to reflect competition for light, light limitation is unlikely for plants with such low photosynthetic potential. Instead, during this early evolution, the capacities of trees for enhanced propagule dispersal, greater leaf area, and deep-rooting access to nutrients and the water table are all deemed more fundamental potential drivers than light.

Tracheophyte of Xiao Hinggan Ling in China: an updated checklist.

BACKGROUND: This paper presents an updated list of tracheophytes of Xiao Hinggan Ling. The list includes 124 families, 503 genera and 1640 species (Containing subspecific units), of which 569 species (Containing subspecific units), 56 genera and 6 families represent first published records for Xiao Hinggan Ling. The aim of the present study is to document an updated checklist by reviewing the existing literature, browsing the website of National Specimen Information Infrastructure and additional data obtained in our research over the past ten years.This paper presents an updated list of tracheophytes of Xiao Hinggan Ling. The list includes 124 families, 503 genera and 1640 species (Containing subspecific units), of which 569 species (Containing subspecific units), 56 genera and 6 families represent first published records for Xiao Hinggan Ling. The aim of the present study is to document an updated checklist by reviewing the existing literature, browsing the website of National Specimen Information Infrastructure and additional data obtained in our research over the past ten years. NEW INFORMATION: This is the first complete checklist of tracheophytes of Xiao Hinggan Ling. A total of 1640 species and subspecies are listed, of which 569 species (ontaining subspecific units) represent first published records.

Photosynthesis Optimized across Land Plant Phylogeny.

Until recently, few data were available on photosynthesis and its underlying mechanistically limiting factors in plants, other than crops and model species. Currently, a new large pool of data from extant representatives of basal terrestrial plant groups is emerging, allowing exploration of how photosynthetic capacity (Amax) increases from minimum values in bryophytes to maximum in tracheophytes, which is associated to an optimization of the balance between its limiting factors. From predominant mesophyll conductance limitation (lm) in bryophytes and lycophytes (fern allies) to stomatal conductance (ls) and lm colimitation in pteridophytes (ferns) and gymnosperms, a balanced colimitation by the three limitations is finally reached in angiosperms. We discuss the implications of this new knowledge for future biotechnological attempts to improve crop photosynthesis.

The early evolution of land plants, from fossils to genomics: a commentary on Lang (1937) 'On the plant-remains from the Downtonian of England and Wales'.

During the 1920s, the botanist W. H. Lang set out to collect and investigate some very unpromising fossils of uncertain affinity, which predated the known geological record of life on land. His discoveries led to a landmark publication in 1937, 'On the plant-remains from the Downtonian of England and Wales', in which he revealed a diversity of small fossil organisms of great simplicity that shed light on the nature of the earliest known land plants. These and subsequent discoveries have taken on new relevance as botanists seek to understand the plant genome and the early evolution of fundamental organ systems. Also, our developing knowledge of the composition of early land-based ecosystems and the interactions among their various components is contributing to our understanding of how life on land affects key Earth Systems (e.g. carbon cycle). The emerging paradigm is one of early life on land dominated by microbes, small bryophyte-like organisms and lichens. Collectively called cryptogamic covers, these are comparable with those that dominate certain ecosystems today. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.