Early flowering plants are thought to have been woody species restricted to warm habitats 1–3 . This lineage has since radiated into almost every climate, with manifold growth forms 4 . As angiosperms spread and climate changed, they evolved mechanisms to cope with episodic freezing. To explore the evolution of traits underpinning the ability to persist in freezing conditions, we assembled a large species-level database of growth habit (woody or herbaceous; 49,064 species), as well as leaf phenology (evergreen or deciduous), diameter of hydraulic conduits (that is, xylem vessels and tracheids) and climate occupancies (exposure to freezing). To model the evolution of species’ traits and climate occupancies, we combined these data with an unparalleled dated molecular phylogeny (32,223 species) for land plants. Here we show that woody clades successfully move di nto freezingprone environments by either possessing transport networks of small

/pdf/three-keys-to-the-radiation-of-angiosperms-into-freezing-19a7okg0a6.pdf

Three keys to the radiation of angiosperms into freezing environments

Stomatal pores are microscopic structures on the epidermis of leaves formed by 2 specialized guard cells that control the exchange of water vapor and CO2 between plants and the atmosphere. Stomatal size (S) and density (D) determine maximum leaf diffusive (stomatal) conductance of CO2 (gcmax) to sites of assimilation. Although large variations in D observed in the fossil record have been correlated with atmospheric CO2, the crucial significance of similarly large variations in S has been overlooked. Here, we use physical diffusion theory to explain why large changes in S necessarily accompanied the changes in D and atmospheric CO2 over the last 400 million years. In particular, we show that high densities of small stomata are the only way to attain the highest gcmax values required to counter CO2“starvation” at low atmospheric CO2 concentrations. This explains cycles of increasing D and decreasing S evident in the fossil history of stomata under the CO2 impoverished atmospheres of the Permo-Carboniferous and Cenozoic glaciations. The pattern was reversed under rising atmospheric CO2 regimes. Selection for small S was crucial for attaining high gcmax under falling atmospheric CO2 and, therefore, may represent a mechanism linking CO2 and the increasing gas-exchange capacity of land plants over geologic time.

https://www.pnas.org/content/pnas/106/25/10343.full.pdf

Maximum leaf conductance driven by CO2 effects on stomatal size and density over geologic time

Fossil in situ spores and pollen grains: an annotated catalogue

The Scientific Committee on Antarctic Research (SCAR) supports discipline- and issue-based meetings in Antarctic research, and these are forums for announcing developments in Antarctic science. Refereed symposia proceedings normally follow and generate a number of volumes that almost constitute serial publication. Meetings in the Earth sciences occur at roughly 4-year intervals. The resulting volumes cover Antarctic Earth science generally and provide convenient access to periodic bibliographic updates.

The Antarctic Region: Geological Evolution and Processes is a collection of the Proceedings of the VII International Symposium on Antarctic Earth Sciences, held in Siena, Italy, in 1995 and sponsored by SCAR. It was by far the largest such meeting held to date—the next will be in New Zealand in 1999—but the book, even as large as it is, contains only a portion of the papers presented.

The Antarctic Region: Geological Evolution and Processes

https://estudogeral.sib.uc.pt/bitstream/10316/3934/4/Hesselbo%20et%20al2007.pdf

Carbon-isotope record of the Early Jurassic (Toarcian) Oceanic Anoxic Event from fossil wood and marine carbonate (Lusitanian Basin, Portugal)

Vegetative plant remains and microsporangiate cones, related to the fossil genera Frenelopsis and Classostrobus respectively, were studied in three localities from the Lower Cretaceous of the Pyrenees and Iberian Ranges (Spain). Sterile remains belong to three different species: F. Rubiesensis Barale, F. Ugnaensis sp. nov. and F. Turolensis sp. nov. The male cones Classostrobus ugnaensis sp. nov. and C. Turolensis sp. nov. are associated with the two latter species respectively, and C. Turolensis is found in connection with F. Turolensis. Internodes of F. Ugnaensis display small hemispherical papillae and long conical hairs covering the entire cuticle surface, while F. Turolensis has a strip of hairs near the leaf margin, in addition to more massive outer stomatal papillae and higher stomatal density. The tiny cones of C. Ugnaensis bear microsporophyll cuticles capped with vermiculate flattened papillae and a fringe of marginal hairs, while C. Turolensis has a central area of microsporophylls covered by long conical hairs. Sedimentological and taphonomic analyses show that the assemblages studied belong to a wide spectrum of habitats. These indicate that Spanish Lower Cretaceous frenelopsids were xeromorphic plants, able to adapt to helophytic and riparian habitats, and grew in brackish coastal marshes and fluvio–lacustrine freshwater environments.

Frédéric Thévenard

Papers

Frenelopsis (Coniferales: Cheirolepidiaceae) And Related Male Organ Genera From The Lower Cretaceous Of Spain

Early Cretaceous angiosperm invasion of Western Europe and major environmental changes.

Distribution and palaeoecology of the Mesozoic wood genus Xenoxylon: palaeoclimatological implications for the Jurassic of Western Europe

Plant taphonomy and palaeoecology in the lacustrine Uña delta (Late Barremian, Iberian Ranges, Spain)

Early Angiosperm Ecology: Evidence from the Albian-Cenomanian of Europe