Transcript Plant Reproduction

Plant
Reproduction
Biotechnology II
Essential Questions
 How
do angiosperms reproduce?
 What defines a model organism?
Angiosperms
 Plants
that produce flowers
 Angiosperms – most diverse group in plant
kingdom. Why?

Evolved flowers and fruits. This allowed
 Increased
successful mating of stationary
organisms
 Flowers protect the egg and improved odds
of fertilization
 Allowed plants that were considerable
distance to mate through pollinators
 Fruit that surrounds the seeds –aided in
dispersal with the help of animals
Development of flower-Why?
 Being
terrestrial and lack locomotion –
poses several problems:

Gametes delicate cells.
 To
achieve cross-fertilization, two gametes
must reach each other safely.

Must have a mechanism for dispersal
 Must
be far enough away from parent so not
to compete for light, water, and soil minerals.
Types of flowers
 Perfect
flower – have both
microsporangia (male) and
megasporangia (female)
 Imperfect flower – have either
microsporangia (male) or megasporangia
(female)
Development of the flower

Develop from flower
buds- each bud has 4
concentric whorl of
tissues
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Whorl of sepals – calyx
Whorl of petals - corolla
Stamens – where
microsporangia(sperm)
form
Carpels – where
megasporangia (egg)
form
Anatomy of the Flower
Sexual Reproduction

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Pollen (contains
sperm)is released
from the anther
Carried to the
carpel, female
reproductive organ
Attaches to stigma
Pollen germinates –
forms pollen tube
Pollen tube carries
sperm to the egg in
the ovule
Sexual Reproduction
 Animation
of pollen germination and
pollen tube growth
Pollination

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Pollen tube when it
reaches ovule –
releases the sperm
Sperm nucleus and
Egg nucleus
combine to become
the zygote
Zygote divides and
forms the embryo
Self-incompatibility
 Many
angiosperms have mechanisms
that prevent self-fertilization by rejecting
its own pollen

Prevent the pollen from germinating
 Promote
genetic variation
Seed

Once fertilized, each
ovule develops into the
seed

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A plumule – made up
of two embryonic
leaves, which
become the first true
leaves of the
seedlings.
Cotyledons
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Dicot – two
cotyledons – ex. bean
seed
Monocot-one
cotyledon- ex. corn
seed
Seed
 Radicle
– primary
root
 Hypocotyl- part of
the stem below
the first node
where the plumule
is attached
Fruits
 Develop
from the
ovary wall
 Seeds
mature
release hormone
auxin –stimulates
the ovary wall to
develop into fruit
Plant Breeding
 Also
known as artificial selection
 Takes advantage of sexual reproduction
in plants
 Collect pollen with desired phenotypic
traits
 Pollinate flowers on neighboring plants
 Majority of Agriculture crops grown today
were developed using artificial selection
Brassica rapa
 Belong
to the mustard family
 Same family as cabbage, cauliflower,
broccoli, and arabidopsis
Economic Importance
 Important
economically as oilseed crop
and animal fodder

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Crucifer oil, known as rapeseed oil, is the
third most commonly traded vegetable oil
in the world
Rapeseed contains 40% oil-released when
the seed is pressed
Remaining seed meal is high in protein and
used in animal feed and nitrogen fertilizer
Development of Rapid
Cycling Brassica
 Wanted
to incorporate efficiently traits of
economic important, such as disease and
pest resistance
 Needed an ideal plant type to speed
research in genetics and plant breeding
 Began to breed Brassica rapa
Breed plants for Selective Traits
 Traits
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included
Minimum time from planting to flowering
Rapid seed germination
Absence of seed dormancy
Small plant size
High female fertility – ovules once fertilized
would develop into seeds rather than abort
Final Product
 Through
this plant breeding created a
plant with a rapid life cycle
 Plant has an average life cycle of 35 days
compared to a normal 6 to 12 month life
cycle
Life Cycle of Brassica
Other traits that make it ideal
as a model organism
 Small
in size; grow many in a small space
 Developed mutants for studying the
growth and development of the plant
Lab Activity
 Use
the model plant, Brassica Rapa, to
monitor seed germination
Answer the following questions
1.
2.
3.
4.
5.
6.
7.
What was the evolutionary significance of flowers?
What organs in the flower are the male (sperm)
gamete and female (egg) gamete found,
respectively
Explain the process by which the pollen fertilizes the
egg.
What does it mean to be self-incompatible?
What is the economic importance of Brassica
rapa?
What is Brassica rapa considered a model organism
for studying plants?
Read pp. 286-292; answer questions on p. 289 and
292.