Download Plant Reproduction - Doral Academy Preparatory

Plant Life Cycles
CHAPTER 30
Animals vs. Plants
Plant Reproduction
Animal
Reproduction
Life cycle
Alternation of
generations
No alternation of
generations
Gametes
Haploid gametes
Haploid gametes
Spores
Haploid spores
No spores
Gametes made Haploid gametophyte, Diploid organism, by
by
by mitosis
meiosis
Spores made
by
Diploid sporophyte, by
meiosis
No spores
Alternation of Generations
• Plants have a double life cycle with two
distinct forms:
– Sporophyte: diploid, produce haploid spores
by meiosis.
– Gametophyte: haploid, produce gametes by
mitosis.
Non-flowering plants
• Mosses, ferns, and related plants have
motile, swimming sperm.
• What kind of environmental conditions
would be required for reproduction in
these plants?
• What kinds of limits does external
reproduction impose on these plants?
Life cycle of mosses
• Follow the link and write down in your
notes 1 page on the life cycle of mosses
http://www.microview.org.uk/millennium/pag
es/moss_lifecycle.htm
http://www.sumanasinc.com/webco
ntent/animations/content/moss.html
Moss Life Cycle
Life cycle of ferns
•
•
•
Ferns, unlike some other plants, do not flower in order to propagate. Instead, they reproduce sexually
from spores.
The life cycle of a fern is very different from the life cycle of many other plants.
While many plants grow a mature adult form straight out of the seed, ferns have an intermediate
stage, called a gametophyte, which then grows into a mature fern.
•
•
There are two distinct stages in the life cycle of ferns. The first stage is that of the gametophyte.
•
Spores are produced on the underside of mature plants. These will germinate and grow into small,
heart-shaped plants called gametophytes.
•
The gametophytes produce both sperm and egg cells, and will fertilize itself, or others. Once the
fertilization occurs, the adult fern will begin growing.
•
The second stage in the life cycle of a fern is the adult stage. The fertilized gametophytes begin to
look like a mossy growth.
Conifers
• Conifers (also non-flowering plants) have
reduced gametophytes.
– Male gametophyte is contained in a dry pollen
grain.
– Female gametophyte is a few cells inside of
the structures that become the seed.
Conifer life cycle
Conifer pollination
• Conifers are wind-pollinated plants.
• Chance allows some pollen to land on the
scales of female cones.
• Pollen germinates, grows a pollen tube
into the egg to allow sperm to fertilize the
egg.
• What are some advantages and
disadvantages to wind pollination?
Flowering Plant Reproduction
Angiosperms (flowering plants)
• Plants that protect their seeds within the body
of a fruit.
• Make up ¾’s of all plants, including:
– Trees, shrubs, herbs,
grasses, water plants…
Structure of a Flower
1. Pistil
2. Stigma
3. Style
4. Ovary
5. Stamen
6. Filament
7. Anther
8. Petal
9. Sepal
10. Receptacle
11. Stem
Male Reproductive Structure
The stamen consists of
two parts: Anther and
Filament
The anther is where
meiosis occurs to
produce haploid pollen
The filament is a stalk
that supports the
anther
Female Reproductive Structure
The pistil consists of
the stigma, style and
ovary
The sticky stigma
receives the pollen
from the anther
The pollen grows a
tube down through the
style
Meiosis occurs in the
ovary to produce
haploid ovules
Reproductive Structures
• Petals: colourful
structures that attract
pollinators.
• Sepals: surround and
protect the flower bud.
Pollination
Wind, insects or other
animals transfer pollen
from the anther of one
flower to the stigma of
another
Flowers vary
depending on
pollination mechanism
Pollination Animation
Pollination Vectors
Wind Pollination: Dull, scentless
flowers with reduced petals
Bees/Butterfly Pollination: Bright
color, nectaries, scent.
They sip nectar, get pollen on coats,
transfer pollen from flower to flower
Bird Pollination: Nectaries, bright
colors, tube-like flowers
Moth Pollination: White petals,
open at night
Fly Pollination:Rank odor, flesh
colored petals
• Pollen Grain
• Anther Sac
Pollen grains contain two haploid cells produced through meiosis.
1- The Tube cell – will grow the pollen tube.
2- The Generative cell – will go through mitosis to create
two sperm cells.
Ovary
Each ovule within an ovary has a micropyle (an opening for the
pollen tube).
The ovules’ megasporangium undergo meiosis to produce four
haploid cells (3 die leaving 1 megaspore)
The megaspore undergoes mitosis 3 times to produce 8 haploid
cells within the embryo sac.
Fertilization
{ After pollen lands on the stigma, a pollen
tube grows down through the style to ovary
{ Generative cell creates the two sperm nuclei
{ Double fertilization occurs:
{ one sperm fertilizes the egg
{ one sperm the two polar nuclei together
Result of Double Fertilization
{ The sperm nucleus and egg nucleus join to
form a 2n (diploid) embryo
{ The other sperm nucleus and the two polar
nuclei join to form a 3n (triploid)
endosperm. The endosperm is the food
supply for the embryo.
{ First link
Seed and Fruit Development
{ After fertilization,
the petals and
sepals fall off
flower
{ Ovary “ripens”
into a fruit
{ The ovule
develops into a
seed
Seed Dispersal MechanismsAllow plants to colonize new areas and avoid
shade of parent plant
Wind Dispersal - Flight mechanisms,
like parachutes, wings, etc.
Ex. Dandelion, maples, birch
Animal Dispersal - Fleshy fruits which
animals eat, drop undigested seeds in
feces or burrs which stick to
animals’ coats
Gravity Dispersal Heavy nuts fall to
ground and roll
ex. acorns
Water Dispersal - Plants
near water create floating
fruits
ex. coconuts
Plant Responses
CHAPTER 31
• How plants move and communicate
Plant Hormones
Plant Hormones
• Plant hormones can be divided into two
classes:
– Growth promoters: Auxins, Gibberellins,
Cytokinins
– Growth inhibitors: Ethylene gas, Abscisic acid
Growth promoters
• Hormones can promote plant growth in
two ways:
– Stimulating cell division in meristems to
produce new cells.
– Stimulating elongation in cells.
Auxins
Auxin activity
Auxins stimulate genes in cells associated with plant growth.
Auxin roles
• Auxins carry out multiple roles having to
do with plant growth including:
–
–
–
–
Tropisms
Apical dominance
Growth of adventitious roots
Fruit growth
Tropisms
• Tropisms are the growth of a plant toward
or away from a stimulus, including:
– Phototropism: in response to light
– Gravitropism: in response to gravity
– Thigmotropism: in response to touch
Nastic Movements
Nastic
movement in
the sensitive
plant (Mimosa
pudica)
Hinge control in Venus Fly Trap - Nastic movement
How it works
• Nastic movements are rapid, reversible
movements in a plant.
• Electrical potentials across cell
membranes, similar to those in our nerve
cells, signal plant cells at the base of the
Mimosa leaf to rapidly lose water. This
causes the leaf to droop.
Movies
• Sensitive Plant:
http://www.youtube.com/watch?v=BVU1
YuDjwd8
• Venus Fly Trap:
http://www.youtube.com/watch?v=ktIGV
tKdgwo&feature=related
Other examples
• Sunflowers follow the sun during the day.
• Leaves of many plants turn to follow the
sun.
Day/Night length
• Some plants flower in response to the
length of periods of darkness.
• Spring-blooming flowers are long night
(short day) plants, while summerblooming flowers are short night (long
day) plants.
• Some plants are day-neutral.
Plant Communication
• Plants communicate chemically.
• Injured plants send out chemical signals
that may
– signal other plants to prepare for an attack.
– attract other insects that eat the insects that are
attacking the plant.