Botany LS1203 - Plant Biology

Vascular Plants

Features of Vascular Plants:
1)  chl a, chl b, carotenoids, starch, cellulose walls
2)  well developed cuticle; functional stomata
3)  lignin:  xylem, fibers, sclereids 
        supported stems allow upright growth on land
        large leaves
        roots for anchorage and absorption
        vascular tissue for conduction of soil minerals and water, sugar
4)  seedless vascular plants require free water in order for sperms to swim to egg
5)  seed plants use pollen grains to transport sperm to female structures housing the eggs – no need for free water for fertilization

Extant Seedless Vascular Plants    
    Ferns (Pterophyta or Polypodiophyta)
    Horsetails (Sphenophyta or Equisetophyta)
    Whisk Ferns (Psilotophyta)
    Club Mosses, Quillwort (Lycophyta)
Note:  These are the phyla used in your textbook. Another classification puts the extant seedless vascular plants in two phyla:  Lycopodiophyta (club mosses, quillwort) and Pteridophyta (ferns, whisk ferns, horsetails)

Reproduce asexually by growing new leaves out of the rhizome each year

Club mosses and horsetails produce a strobilus = a step tip with several closely spaced leaves with sporangia.  Forerunner of the cones of conifers and the flower.

Whisk Fern (Psilotum)
no roots; have rhizomes with absorptive rhizoids; mycorrhizae
no obvious leaves; sporangia are little balls near stubs where you would expect leaves
photosynthetic stems, dichotomous branching

Club Mosses/Ground Pines (Selaginella,  Lycopodium [resurrection fern])
have strobili (the “club” part)
this group also includes the quillworts (Isotes); some species of quillworts have CAM photosynthesis

Horsetails (Equisetum)
Equisetum is the only living genus; 15 known species.
Silica in the cell walls  ==>  scouring rush
found worldwide in moist habitats, including the damp areas on lower campus near the Social Sciences building

Has true stems, roots, and leaves, but the leaves are very reduced.  The stem is the primary photosynthetic organ

The spores have attached elaters.  Sporangia in a terminal strobilus.

Ferns
the largest group of seedless vascular plants
circinate vernation = the curling of young fern leaves (fronds), i.e. “fiddleheads”

no strobilus.  Spores form on leaves in structures called sori.  Some sori are covered by an indusium.  The leaves with sori are often called sporophylls.

Tree ferns grow in a tree-like habit; some can grow over 30 feet tall.


Economic Botany of the Seedless Vascular Plants
Azolla (water fern) + Anabaena (a cyanobacterium) - nitrogen fixation in rice paddies 
Ferns used as ornamentals - indoors and out. 
        As house plants, ferns are less prone to pests than flowering plants.  Also, ferns make good filters for indoor air pollutants. 
edible ferns:  fiddleheads, starchy rhizomes, the starchy core of tree ferns
Tree Ferns - the "bark" is used as a growth medium for epiphytes (orchids, bromeliads, staghorn ferns)
Lycopodium, other club mosses:  
        spores - flash powder for photography and theatrical effects; to coat capsules and tablets to prevent sticking 
        landscaping, interior decor 
        resurrection fern - shows poikilohydry
Equisetum - scouring rush
fossil fuel deposits (from tree-like seedless vascular plants of the Carboniferous period, roughly 290-360 million years ago)

Extant Seed Plants
    Gymnosperms and Angiosperms

   Conifers (Pinophyta) = the cone bearers:  pine, spruce, fir, redwood, cedar, juniper
    Cycads (Cycadophyta) = cycads, sago palm (not true palms, which are angiosperms)
    Ginkgo (Ginkgophyta) = Ginkgo biloba  is only extant species
    Gnetophytes (Gnetophyta) =  includes Ephedra (Mormon tea), Welwitschia, and Gnetum 
    Flowering plants (Magnoliophyta)

The importance of a seed:
    embryo = multicelled miniature plant
    food supply = either endosperm or fleshy cotyledons
    dormancy = certain maturation or environmental conditions must be met before seed can germinate. 
    dispersal = generally via fruit in the angiosperms

With the seed plants, plants lose dependence on free water for fertilization.  The pollen grain carries the sperm to the ovules, where the eggs are located.  Pollen is carried by a variety of pollination vectors, including wind, insects, mammals, and birds.

Two opportunities for genetics material to travel long distances:  pollen grains, seeds

Distinctive Conifers 
tallest plant:  California or coastal redwood,  Sequoia sempervirens
largest volume plant:  giant sequoia, Sequoiadendron giganteum 
oldest plant:  bristlecone pine,  Pinus longaeva 
all are native to California

Economic Botany of the Seed Plants
secondary growth of conifers
    pulp for paper manufacturing 
    lumber
        Douglas fir because of the low incidence of knots
        redwood,  cedar, and bald cypress because of natural resistance to fungi, bacteria, and insects
        spruce for stringed instruments
pines:  resin:  turpentine, rosin (naval stores) 
edible pines:  inner bark, pine "nuts" 
yews:  English yew - the long bow; Pacific yew - Taxol  
Ginkgo:  seeds are edible; extracts are popular supplements 
Cycads:  landscaping, Botanic Gardens; "living fossils" 
Flowering Plants:  hardwoods, fruits, grains, legumes, floral industry, herbs and spices, beverages, vegetables, textiles, dyes, medicines, etc.

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27 November 2006