Transcript Plants 3 - codyzesiger

Plants 3
Modified from Dr. Sue Hartley’s BTNY1203
Divisions of plants
Non vascular
• Mosses
• Liverworts
• Hornworts
• algae
Vascular
• Nonseeded e.g. ferns
• Seeded i.e. angiosperms and
gymnosperms.
Gymnosperms
Conifers (Pinophyta or Coniferophyta): the cone bearers;
include pine, spruce, fir, redwood, cedar, juniper, yew
Cycads (Cycadophyta): cycads, sago palms (not true palms,
which are angiosperms)
Ginkgo (Ginkgophyta): Ginkgo biloba is only extant species
Gnetophytes (Gnetophyta) = only gymnosperms with
vessels in the xylem: Ephedra (Mormon tea), Welwitschia
mirabilis (only species), and Gnetum
What is a gymnosperm?
Gymnosperm: the naked seed.
plants that do not
enclose their seeds in an ovary.
Do gymnosperms produce fruit?
Conifers
Conifers are native to places with harsh winters: high elevations
and northern latitudes. During the winter, the humidity is very low,
and liquid water is scarce. Many conifers are evergreen, so keeping
their leaves through winter poses a threat of serious water loss by
transpiration. Needle-like and scale-like leaves have a low surface
area relative to leaf volume. This decreases transpiration. Various
other structure features of the conifer leaves decrease transpiration,
including sunken stomata, a thick cuticle layer, a hypodermis, and an
endodermis (Figure 7.12).
By having xeric-adapted leaves, conifers can enjoy the benefits of
being evergreen while minimizing water loss. With a short growing
season, evergreens can use any chance to do photosynthesis and
other aspects of metabolism. For northern and high latitude conifers,
photosynthesis does not stop until air temperatures drop below about
20oF (-6oC), the temperature at which they no longer have liquid
cellular water.
Cycads
Cycads are dioecious, with male strobili on
one plant and
female strobili on another.
Ginko
Ginkgo biloba is dioecious, with male
structures produced on one tree and
female on another. Usually when the
tree is planted as an ornamental, males are
used because the females produce a seed
with a fleshy seed coat that has an odor that
most people find offensive.
The fan-shaped leaves are deciduous.
Gnetophytes
Ephedra grows in the southwest deserts of
North America. It is dioecious. The upper
photo shows a pollen-producing male
structure. The two lower photos show
female
Plant
Welwitschia
Angiosperms
•reproductive structures in a flower
• seed is covered by a fruit formed from
the ovary and accessory floral parts
• the fruit protects the seed during
development and provides a means to
disperse the mature seed
– monocots
– eudicots
Dicots
Petals and sepals in sets of four or five
Leaf veins not parallel