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Mesozoic “The Age of Cycads” The “age of conifers”? Many groups rapidly evolving during this time. Coniferales Conifers– conebearing plants Araucaria araucana – monkey puzzle tree Tsuga canadensis Conifers among seed plants Seed Plants Angiosperms 1. Seed Ferns 2. Cycads 3. Ginkgo 4. Conifers 5. Gnetophytes 6. Flowering Plants Ginkgo Cycads Gnetales Conifers • Order: Coniferales – Family: Araucariaceae – Family: Podocarpaceae (incl. Phyllocladaceae) Southern Hemisphere – Family: Cupressaceae (incl. Taxodiaceae) – Family: Taxaceae/Cephalotaxaceae – Family: Sciadopityaceae – Family: Pinaceae Northern Hemisphere Growth habits of conifers Cupressaceae Sequoiadendron –big tree Podocarpaceae Dacrydium guillaminii – endangered shrub Araucarian conifers on Les ÎIes des Pins, New Caledonia Agathis lanceolata Agathis ovata Araucariaceae New Caledonian endemics Podocarpaceae Parasitaxus ustus – the only known parasitic conifer Leaf variability in conifers Agathis Araucaria Araucaria Araucariaceae Sequoia taxodiaceous Cupressaceae Picea (spruce) Pinaceae Tsuga canadensis leaves Pinaceae needle-like C U P R E S S A C E A E Taxodium Larix (larch) short shoots with large number of leaves/fascicle – Pinaceae Leaves abscise in the winter Pinus strobus showing short shoots (=dwarf shoots) with fascicles of needles Pinus sylvestris Long shoot bearing short shoots in the axils of scale leaves Pinus leaves in fascicles 2 5 needles/fascicle 5 3 Pinus leaves Hypostomatic= stomata on the abaxial surface only Amphistomatic= stomata on both leaf surfaces Adaxial surface Abaxial surface Two-needle pine leaf x.s. hypodermis r r transfusion tissue x ph plicate mesophyll r endodermis stoma resin canal (r) epidermis Two-needle pine leaf x.s. – amphistomatic Pinus leaf x.s. Pinus leaf ph vascular bundle Abaxial epidermis - sunken stoma R g.c. x Resin canal with thinwalled epithelial cells Plicate mesophyll Hypodermis Guard cell Subsidiary cell Epidermis Cuticle Transfusion tissue outside the vascular bundles Pine needle x.s. in area of the vascular bundle and endodermis Transfusion tissue inside endodermis mesophyll p. endodermis t.t. parenchyma transfusion tracheid t.t. t.t. transfusion tissue v.b. Pinus monophylla Five-needle pine External resin canals i.e., touching the epidermis Scanning electron microscopy of cuticles of Pinus leaves Pinus resinosa Pinus contorta gc gc Pinus virginiana Pinus elliottii Whang et al. 2004 Young Pinus stem x.s. Primary xylem is endarch Pine twig – very young stage – first year Cortex Pinus stem x.s. Pinus wood sections Pinus wood block showing sections and appearance of cells Transverse section = (cross section) Epithelial lining shows the tracheids in x.s. long section of rays Pinus wood Transverse (cross) section of pine wood Circular bordered pits are on the radial walls of tracheids Radial longitudinal section r.l.s. showing the height of rays and the circular bordered pits on the radial walls Rays look like a brick wall Circular bordered pits on radial walls of tracheids Tangential longitudinal section of wood showing height and width of rays Uniseriate rays = rays that are one cell wide Biseriate rays = rays that are two cells wide Multiseriate rays = rays that are a number of cells wide (multiseriate) (uniseriate) Tangential longitudinal section t.l.s. t. l. s. side view of circular bordered pits What wood section is this? What wood section is this? Radial longitudinal section Pine wood radial longitudinal section (r.l.s.) Pine wood has ray tracheids in addition to the parenchyma in the rays Circular bordered pits Differences in pitting between tracheid to tracheid pitting and ray to tracheid pitting Secondary phloem Not all conifers have leaves like this – in fact, most do not Podocarpus leaf x.s. Araucaria heterophylla – Norfolk Island Pine Araucariaceae Agathis Araucaria
