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Plants Day 3
PLANT REPRODUCTION
• Plants complete their life cycle by
alternating between two phases.
• Diploid Phase: plant produces
spores.
• Haploid Phase: plant produces
gametes.
PLANT REPRODUCTION
• Life cycle phases look different among various plant groups.
• Life Cycle of Nonvascular Plants: Moss
• Nonvascular plants have a dominant gametophyte (haploid) phase is dominant and
require water to reproduce.
PLANT
REPRODUCTION
PLANT REPRODUCTION
• Life Cycle of Seedless Vascular Plants: Ferns
• The sporophyte (diploid) phase is dominant phase.
• Sori are clusters of sporangia (spore-producing sacs) that are found on
the underside of the fern leaf.
• A mature sporophyte is called a fiddle head.
PLANT
REPRODUCTION
PLANT REPRODUCTION
• Life Cycle of Seed Plants: Conifers
• The sporophyte (diploid phase) is the dominant phase.
• Produce two types of spores that develop into male and female gametophytes (pollen is
produced in male cones, while eggs are produced in female cones).
• Pollination occurs in a cone-bearing plant when a pollen grain reaches the small opening
of an ovule in the female cone. After pollination, eggs are produced inside the ovule and
a pollen tube begins
PLANT REPRODUCTION
PLANT REPRODUCTION
• Life Cycle of Seed Plants:
Flowering Plants
• Flowers contain reproductive
organs protected by specialized
leaves.
• The outermost layer of a flower is
made up of sepals. Sepals are
modified leaves that protect the
developing flower, collectively
called the calyx.
PLANT REPRODUCTION
• Petals are the modified leaves inside of sepals. Their bright colors
often help to attract animal pollinators. (Petals collectively are also
called the corolla.)
PLANT REPRODUCTION
• Flowers can be a single sex or contain both.
• A stamen is the male structure of a flower.
• The stamen includes:
• filament (holds up anther)
• anther (produce pollen)
anther
filament
stamen
PLANT REPRODUCTION
• The female structure is called a carpel.
• Flowers can have several carpels fused together called a
pistil.
• Structure of pistil:
• stigma (sticky; where pollen lands)
• style (tube that leads to ovary)
• ovary (female reproductive structure)
stigma
style
pistil
ovary
Fruits:
• Can be derived from an ovary and sometimes other flower parts
• As a fruit develops, the ovary wall thickens to form the pericarp
(divided into up to 3 layers: exocarp, mesocarp, endocarp)
• Simple fruits: derived from a single ovary or compound ovary of
several fused carpels. ex. Legumes: peas, beans
• Fleshy fruits: thick fleshly mesocarp. ex. peaches, cherries,
tomatoes
• Accessory fruits: bulk of fruit is from receptacle instead of ovary. ex.
Apples
• Compound fruits: develop from several ovaries. ex. Blackberries,
raspberries
• Aggregate fruit: many separate carpels. Ex. Strawberries
• Multiple fruit: different carpels that belong to several flowers that
as the ovaries mature, they fuse together. ex. pineapples
PLANT REPRODUCTION
• Flowers allow for more efficient pollination than
occurs in most gymnosperms, which rely on wind
for pollination.
• Insects and other animals feed on pollen or nectar and
transfer pollen when feeding.
PLANT REPRODUCTION
• Fertilization takes place within the flower.
• Pollination
• One cell in the pollen grain grows into a pollen tube that extends toward the
ovule.
• The other cell in the pollen grain divides by mitosis, producing two sperm that
travel down the pollen tube. One fertilizes the egg.
• The other sperm combines with the polar nuclei to become a cell with a
triploid (3n) nucleus that will become the endosperm, a food supply for the
developing plant embryo.
• The process is called double fertilization which only happens in flowering plants.
PLANT REPRODUCTION
• Fruits and Seed Dispersal
• The function of fruit in flowering plants is to help disperse
seeds to eliminate competition with parents.
• Animals, wind, and water can spread seeds.
• Examples:
• Bird eats a blackberry and defecates out the seed away
from the bush.
• Dog gets burr in fur and scratches it off in a new
location.
• Dandelion fluff is actually a fruit with a seed attached
and is spread by the wind.
• Coconuts float thousands of miles across oceans and
arrive on different islands.
PLANT REPRODUCTION
• Seeds will not grow until conditions are favorable. This period before growth is
called dormancy.
• Examples: Strawberry seeds remain dormant until their seed coats are weakened in
the digestive tract of an animal. Other seeds have waterproof seed coats that can
only be cracked by winter ice.
PLANT REPRODUCTION
• When a seed begins to grow it
is called germination.
• Embryo takes up water and
breaks out of seed coat.
• Seedling growth begins.
• Enzymes are activated inside
the seed to help digest the
endosperm.
PLANT REPRODUCTION
• Plants can reproduce
asexually with from a
fragment of a stem, leaf,
or root.
• Example: prickly pear
cactus
PLANT REPRODUCTION
• Vegetative reproduction is a
type of asexual reproduction in
which stems, leaves, or roots
attached to the parent plant
produce new individuals.
• Example: aspen trees