Transcript Unit XI: Plant Structure and Function

Plant biology, perhaps the oldest branch of science, is
driven by a combination of curiosity and need
curiosity about how plants work
need to apply this knowledge judiciously to feed, clothe,
and house a burgeoning human population.
Plant Reproduction
Alternation of Generations

Sporophyte
(diploid)
• produces haploid
spores via meiosis

Gametophyte
(haploid)
• produce haploid
gametes via
mitosis

Fertilization
• joins two gametes
to form a zygote
 Monocots
and Dicots
• named for the number of
cotyledons present on the
embryo of the plant
• Monocots




Orchids
Palms
Lilies
Grasses
• Dicots
 Roses
 Beans
 Sunflowers
 Oaks



Sporophyte (diploid)
• actual plant with
flowers
Gametophyte
(haploid)
• male: germinated
pollen grain
• female: embryo
sac
Fertilization
• joins two gametes
to form a zygote



Gametophyte
• dominant generation
• has both sexes and produces
gametes
 archegonia (eggs)
 antheridia (sperm)
Fertilization
• sperm move along moss to
find archegonia
Sporophyte
• grows on top of gametophyte
• sporangia is where spores
are produced by meiosis



Sporophyte
• produce spores via
meiosis
• spores develop into
young gametophyte
Gametophyte
• has both sexes and
produces gametes
 archegonia (eggs)
 antheridia (sperm)
Fertilization
• similar to mosses


Sporophyte
• produce gametophytes
inside of cones
• Pollen cone (male)
 produces microspore via
meiosis
• Ovulate cone (female)
 produces megaspores via
meiosis
Fertilization
• pollen grains discharge
sperm into egg


Male Gametophyte
• pollen grain
 microspores
produced within the
anther
 divide once to
produce two sperm
cells
FemaleGametophye
• embryo sac
 megaspore produced
within the ovule
 divide to produce
three egg cells and 2
polar nuclei

Pollen grain lands on stigma

Pollen tube toward ovule

Both sperm discharged down the
tube

Egg and one of the sperm
produce zygote

2 polar nuclei and sperm cell
produce endosperm

Ovule becomes the seed coat

Ovary becomes the fruit
The most common anti-selfing mechanism in flowering plant is
known as self-incompatibility, the ability of a plant to reject its own
pollen
Stigma
Stigma
Pin flower
Thrum flower
Anther
with
pollen
 The
radicle is the
first organ to
emerge from the
germinating seed
Foliage leaves
Cotyledon
Epicotyl
Hypocotyl
Cotyledon
Cotyledon
Hypocotyl
many eudicots a
hook forms in the
hypocotyl, and
growth pushes the
hook above ground
Hypocotyl
 In
Radicle
Seed coat
 Monocots
use a
different method
for breaking
ground when
they germinate
coleoptile
Pushes upward
through the soil
and into the air
Foliage leaves
Coleoptile
Coleoptile
 The
Radicle