Nonflowering Seed Plants Chapters 21 & 22 Seedless Vascular and Nonflowering Seed Plants

Topics Rhyniophytes Evolution of stele – protostele and syphonostele Vascular plant cladogram Phylum – Lycophyta Phylum – Pteridophyta – life cycles Adaptive superiority of the seed Gymnosperm phyla

Early Vascular Plants: Extinct Rhyniophytes Cooksonia spp. - branching sporophyte – homosporous Rhynia and Aglaophyton were other Rhyniophytes, early vascular plants similar to Cooksonia Today sporangia on vascular plants are lateral – not terminal

Early Vascular Plants Similarities between the hornworts and vascular plants make Anthoceros the possible ancestors of vascular plants – inner vascular cylinder = stele Protostele (solid – no pith) evolved first – two types Endarch – central protoxylem Exarch – central metaxylem Lycophyte roots Lycophyte stems, seed plant roots epidermis epidermis cortex cortex stele

Later another type of stele, siphonostele – central pith - stems of ferns and seed plants - will discuss in plant tissues later Microphylls from enations/scales Megaphylls from branch systems

(ground pine, club moss) Phylum - Lycophyta Lycopodium sp. (ground pine, club moss) Selaginella sp. Label – Strobilus axis, microsporangium, megasporangium, seta, microsporophyll, megasporophyll, microspores, megaspores HETEROSPORY Label – Strobilus axis, sporangium, seta, sporophyll, spores HOMOSPORY

Phylum - Pteridophyta – Ferns and allies Psilotum spp. Whisk ferns

Equisetum spp. Horsetails Strobilus

Ferns - >12,000 spp. Fern stem Fern root

Ferns: Life Cycle

Seed – superior propagation Gymnosperms Seed – superior propagation Heterospory - Megasporangium to megaspore to megametophyte to archigonium – all in ovule = egg and other cells = megagametophyle - retained inside the maternal sporophyte Fertilized ovule = sporophytic embryo - could use the photosynthetic and absorptive capacity of leaves and roots of mother sporophyte – rather than depending on a tiny haploid gametophyte Seed ferns are all extinct

Seed Fertilized ovule covered by its integument - seed coat Embryonic sporophyte Nutritive tissue to nourish sporophyte Dormant period Not covered by an ovary = Gymnosperms Gymnosperms <1000 spp. Four phyla

Phylum - Cycadophyta: Cycads Only ~100 species today Almost all tropical Dioecious – seed cones and pollen cones on separate plants

Phylum Coniferophyta = Pinophyta Most diverse Gymnosperms - >550 spp. All moderate to extremely large trees (Sequoia spp. - largest organisms on planet) Mainly monoecious

Phylum - Ginkgophyta: Maidenhair Tree single living species, Ginkgo biloba Broad leaves – veins dichotomously branched – not reticulate Dioecious – seeds not on cones – emits butric acid – foul odor Native to China – medicinal uses

Phylum - Gnetophyta ~ 70 spp. Gnetum spp. Ephedra spp. Vessels and sieve tubes Similarity to Anthophytes Many – dioecious some - monoecious Welwitschia mirabilis Only sp. in genus