Download 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