Plantae
Seed Plants
Vascular Plants
Formation of vascular tissue
– Xylem (water)
– Phloem (food)
– True leaves, roots, and stems
 Lignin
 Sporophyte generation dominate

Alternation of Generation
Alternation of Generation
Sporophyte dependent on gametophyte
– mosses
 Large sporophyte and small
independent gametophyte
– ferns
 Gametophyte dependent on sporophyte
– seed plants

Why be Sporophyte
Dominant?

Reduced mutations
– UV light harmful to DNA
– Diploid (2n) form copes better with
mutations
two alleles
Why Retain Gametophyte
Generation?
Ability to screen alleles
– doesn’t require a large amount of
energy
 Sporophyte embryos rely on some
gametophyte tissue

Seeds


A seed is a sporophyte in a
package
– spores are only single
cells
– packaged with food
All seed plants are
heterosporous
– megasporangia
– microsporangia
From Ovule to Seed
Overview of Seed Plants
Produce Seeds
– Can remain dormant for years
– Pollination replaces swimming sperm
 Gametophyte generation reduced
– Gymnosperms lack antheridium
– Angiosperms lack both archegonium
and antheridium

Phylogeny
Gymnosperms
(Naked Seed)
Division:
 Division:
 Division:
 Division:

Cycadophyta
Ginkgophyta
Gnetophyta
Coniferophyta
Ginkgophyta




Ginkgo or Maidenhair
Tree
Characteristic leaves
Only one species
Only males are planted
Cycadophyta




Cycads
Palm-like plants
– Sago Palms
Leaves in cluster at
top of trunks
True Secondary
growth
Gnetophyta



3 Genera
Ephedra
Mormon Tea
– Ephedrine
raises heart
rate
raises blood
pressure
Coniferophyta
Coniferophyta


Pine tree is the
sporophyte generation
Contains both male and
female cones
– Pollen (staminate)
cones (low in tree)
 produces pollen
– Ovulate cones (high
in tree) with scales
 produces seeds
Pine Life Cycle

No Antheridium (microsporangia)
produce pollen grain (4 cells)
–2 prothallial cells
–1 generative cell
• become a sterile cell and a
spermatogenous cell
• produces 2 sperm
–1 tube cell
–wings for dispersal
Pine Life Cycle

Ovule in a ovulate cone
– integument (seed coat) (2n)
– megasporangia (meiosis) or nucellus
(nutrition) (2n)
– produces 4 megaspores (3 die)
develops into female gametophyte
–archegonium with eggs (n)
Angiosperms
Angiosperm
Flower



Sepals
Petals
Receptacle


Stamen
– Anther
– Filament
Carpel
– Stigma
– Style
– Ovary with ovule
Angiosperm Life Cycle
Angiosperm Life Cycle

No Antheridium (microsporangia)
produce pollen grain
–1 generative cell
• produces 2 sperm
–1 tube cell
Angiosperm Life Cycle

Ovule in Ovary
– megasporangia
– produces 4 megaspores (3 die)
develops into female gametophyte
called the embryo sac
Angiosperm Life Cycle

Inside embryo sac
– 7 cells (eight nuclei) due to 3 mitotic
divisions
3 antipodals
2 polar nuclei (one cell)
2 synergids
1 egg
Angiosperm Life Cycle
Double fertilization
– one sperm unites with egg
– one sperm unites with polar nuclei
develops into endosperm (3n)
 Fruit and Seed development
– ovule = seed
– ovary = fruit

Cross Pollination

Most flowers do not self-pollinate
– stamen and carpal may develop at
different times
– stamen and carpal may be arranged
in flower to avoid contact
Angiosperm Radiation
Begins the Cenozoic era (65 mya)
 Most closely related to the Gnetophyta
 Coevolution
– the mutual influence of two species
on each other
– plants and animals (insects, birds,
bats)

Pollination
Dispersal
The Global Impact
Transformed atmosphere
– reduced carbon dioxide
– cooled the earth
 Nonrenewable resource
