3. Gymnosperms
Most gymnosperms have
– literally: "naked seeds"
• (no protective fruit/nut)
– needles or scales rather than leaves
– deep-growing root systems
• Cycads (Cycadophyta)
– palm-like trees of tropics/subtropics
• Ginkoes (Ginkgophyta)
– only one species: Ginkgo biloba
• Gnetophytes (Gnetophyta)
– Over 70 species in 3 genera
– trees, shrubs & vines
– found in arid deserts or rain forest
• Conifers (Coniferophyta)
– cone bearing trees, evergreens
– pine, fir, spruce, cedar, juniper, etc.
4.
5. Gymnosperms - Conifers
• Vascular
– deep roots
– woody stems (can be tall)
– waxy scales or needleshaped leaves
• Evergreen (usually)
• Grow in dry, cool climates
• Produce seeds in cones
– male cones produce pollen
– pollen transported by wind
– female cones, once fertilized,
produce seeds
6.
7. Angiosperms - Flowering Plants
• Literaly "seed in a vessel"
– Produce seeds in "fruits"
– fruit, nut, veggie, etc.
– flowers containing ovaries
produce seeds
• Vascular
– roots, stems & leaves
– amazing variety
8. Flower Anatomy
• Flowers are the
reproductive organs
(gametophyte stage) of
angiosperms
– Stamen
• holds pollen (male sex
cells)
– Carpel
• holds ovule (female
sex cell)
– Petals
• attract insects for
pollination
• Pollination occurs when
pollen is transferred to
stigma
– 1st step to fertilization
9. Methods of Pollination
• Bees, flies, butterflies,
hummingbirds
– Feed on nectar & pollen
– Attracted by color & smell
• Wind
– Huge amounts of
pollen form clouds
10. Form & Function of Pollen
• The shape and form of pollen is related to its
method of pollination…
• Insect-pollinated species
have sticky or barbed
pollen grains
• Wind-pollinated species
is lightweight, small and
smooth (corn pollen)
11. Fertilization
• Pollen sends “tubes” down style
to join with ovule(s)
• Fertilized ovule(s) becomes seed
(embryo)
• Ovary becomes fruit
– food source for embryo
• Seeds remain dormant until
germination (when seeds sprout)
– sprout is sporophyte stage of plant
16. Dicots
• Two seed-leaves
• Branching veins
• Woody or herbaceous
stems
• Petals in 4’s or 5’s
• i.e. trees, roses
17. Germination
• Environmental conditions required before a seed
will sprout:
– Temperature
• for adequate
metabolism & growth
– Moisture
• seed will swell & soften
when water is present
– Oxygen
• required for cellular
respiration
– Other factors:
• passage of time,
chilling, light exposure
18. Tropisms
• Tropisms describe any plant growth toward or away from
an external stimulus
– phototropism
• toward light
• into soil (away from light)
– gravitropism
• downward (roots)
• upward - stems
– negative, against gravity
– thigmotropism
• response to touch
– hydrotropism
• movement in response to a concentration gradient
• Plant movement & growth is controlled by hormones
Tropisms Video
19. Plant Hormones
• Hormones are chemicals in plants that affect:
–
–
–
–
–
growth of roots, stems, leaves
seed germination
ripening of fruit
formation of flowers
shedding of leaves
• The hormone auxin
influences the rate
division
meiosis)
of cell
(mitosis &
Hormone Video
"naked" seeds because they are not enclosed in a protective covering (such as a nut or fruit).
Cycad - sago palm, found when dinosaurs lived
Gnetophyta (nee-tuh-fyts): Welwitschia (top), Ephedra (bottom right),
Top right is dandelion pollen
Germination is the start of growth in the seed. Three factors are required for successful germination:
Water - allows the seed to swell up and the embryo to start growing
Oxygen - so that energy can be released for germination
Warmth - germination improves as temperature rises (up to a maximum)
About less than 105 are woody and the rest of the 30,000 species are herbaceous.
Stems have vascular bundles scattered throughout.
Roots are adventitious (branching)
About half of the 200,000 species are woody and the other half herbaceous.
Stems have vascular bundles in a ring around outer edge.
Roots are primary (taproot) and adventitious (branching)
Why would a seed NOT germinate if lacking these conditions?
3 groups of seeds are grown in a cardboard box.
A - when the tips are removed, no auxin is made so the stems do not grow
B – when the tips are covered, auxin moves to all parts of the stem causing all parts to grow
C - when the tips are lit from one side only auxin accumulates on the shaded side causing it to grow more than the illuminated side