Transcript Gymnosperms
Gymnosperms Key Characteristics Vascular, seed bearing plants that lack flowers “gymno” = naked, “sperm” = seed Most features based on reproduction Seeds and microsporangia on strobili Pollen transferred from microsporangia to ovules Ovules exposed (naked) Ovules and seeds covered by sporophylls Colder more temperate climates Physiology similar to angiosperms Typically evergreen, some deciduous species Ecology of Gymnosperms Like those of flowering plants, but narrower set of features and habitats Pinophyta well adapted to colder climates: – Northern forests mostly pine and relatives – Southern forests mostly araucaria and relatives Some gymnosperms lives in deserts; such as Ephedra, Welwitschia, and pinons A few a tropical; ex. The cycads and Gnetum Typically adapted to where free water is scarce Sunken stomata, thick cuticle and tough hypodermis Four Major Divisions of Gymnosperms Ginkophyta (maidenhair tree) Cycadophyta (cycads) Pinophyta (conifers) Gnetophyta (gnetophytes) 65 genera includes 720 species Division Ginkophyta Only one living species, Ginkgo biloba Exclusively dioecious (separate sexes) Flagellated sperm Haustorial pollen tubes (do not convey sperm) Fleshy integuments around seeds Deciduous simple leaves Seeds on simple seed stalks Two types of leaves Nearly extinct Division Cycadophyta ~10 genera and 100 species Tropical and subtropical Exclusively dioecious Most species threatened Flagellated sperm Large strobili, fleshy integument Palm-like leaves dissimilar to any other gymnosperm, persistent Haustorial pollen tubes and flagellated sperm Division Pinophyta Generally called conifers or cone bearing Largest division with greatest number of species Most abundant trees in northern hemisphere Oldest living plants Have short shoots, long shoots and two types of leaves Pine needle, occurs in clusters called fascicles Tree completely replaces needles ~ 5 years Evergreens Life cycle is extended, may last up to 20 months Division Gnetophyta Very distinctive (bizarre) seed plants 3 genera and 71 species Genera include – Ephedra (40 species) – Gnetum (30 species) – Welwitschia (1 species) Leaves small and generally non-photosynthetic Dioecious Tropical only Use pollen tube for transport of sperm Double fertilization (only ones among gymnosperms) Economic Importance In northern hemisphere = use of wood for making paper and lumber Resins, rosins, turpentine and amber