Transcript Photosynthesis

Chapter 28
Reproduction in
Plants
Outline
Reproductive Strategies
Alternation of generations
Adaptation to a land environment
Flowers
- Pollination
- Fertilization
Seed Development
Fruit
Seed Germination
Asexual Reproduction
Tissue Culture
Reproduction in
Plants
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Reproductive Strategies
Reproduction in
Plants
All plants have a two-stage, alternating life cycle
Sporophyte produces haploid spores by meiosis
Spores divide mitotically to become haploid
gametophytes
Gametophytes produce gametes
Gametes fuse to produce zygote
Zygote divides mitotically to become diploid
sporophyte
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Alternation of Generations
in Flowering Plants
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Reproductive Strategies
Reproduction in
Plants
Flower produces two types of spores
Microspore - Male gametophyte
- Undergoes mitosis
- Becomes pollen grain
Megaspore - Female gametophyte
- Undergoes mitosis
- Becomes embryo sac within an ovary, within an
ovule
- Ovule becomes seed
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Flowers
Reproduction in
Plants
Flower develops in response to environmental
signals such as day length
In monocots, flower parts occur in threes and
multiples of three
In eudicots, flower parts occur in fours or fives
and multiples of four or five
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Anatomy of a Flower
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Monocot vs. Eudicot Flowers
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Flowers
Reproduction in
Plants
Leaf-like sepals protect the bud
Open flower has whorl of petals
Four whorls of modified leaves attached to a
receptacle at the end of a flower stalk
- Receptacle with a single flower is a peduncle
- Receptacle with several flowers is a pedicle
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Flowers
Reproduction in
Plants
Leaf-like sepals protect the bud
Open flower has whorl of petals
Four whorls of modified leaves attached to a
receptacle at the end of a flower stalk
- Receptacle with a single flower is a peduncle
- Receptacle with several flowers is a pedicle
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Flowers
Reproduction in
Plants
Stamens are male portion of flower
Anther - Saclike container
Filament - Slender stalk
Carpel is female portion of flower
Stigma - Enlarged sticky knob
Style - Slender stalk
Ovary - Enlarged base enclosing ovules
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Flowers
Reproduction in
Plants
Complete vs. incomplete flowers:
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Complete flowers have sepals, petals, stamens,
and a carpel
Incomplete flowers missing one or more of above
Bisexual vs. unisexual flowers:
Bisexual flowers have both stamens and carpel
Unisexual flowers have one but not the other
Monoecious vs. dioecious plants
Monoecious plants have staminate flowers and
carpellate flowers on the same plant
Dioecious plants have all staminate or all
carpellate flowers
Corn Plants are Monoecious
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Life Cycle of Flowering Plants
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From Spores to Fertilization
Reproduction in
Plants
Male Gametophytes
 Microspores are produced in anthers
 Each anther has four pollen sacs, each with
many microsporocytes
- Undergoes meiosis to produce microspores
- Mitosis produces pollen grains
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Pollination
Reproduction in
Plants
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Pollination is the transfer of pollen from an anther
to the stigma of a carpel
Self-pollination occurs if the pollen is from the
same plant
Cross-pollination occurs if the pollen is from a
different plant
Pollination
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Reproduction in
Plants
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Production of Female Gametophyte
Ovary contains one or more ovules
Ovule has mass of parenchyma cells
One cell enlarges to become megasporocyte
- Undergoes meiois and becomes four haploid
megaspores
- Functional megaspore divides mitotically until there
are eight nuclei of a female gametophyte
Fertilization
Reproduction in
Plants
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When pollen grain lands on stigma, it germinates
forming a pollen tube
Passes between the stigma and style to reach
the micropyle of the ovule
Double fertilization occurs
One sperm nucleus unites with the egg nucleus,
producing a zygote
Other sperm nucleus unites with the polar nuclei,
forming a 3n endosperm cell
Seed Development
Reproduction in
Plants
Development of eudicot embryo
After double fertilization, endosperm nucleus
begins to divide asymmetrically
Small cell is destined to become the embryo
Larger cell divides repeatedly to become a
suspensor
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Development of a Eudicot Embryo
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Monocot vs. Eudicot
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Reproduction in
Plants
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Development of Eudicot Embryo
During globular stage, prembryo is ball of cells
Outermost cells will become dermal tissue
Embryo is heart shaped when cotyledons appear
Epicotyl is portion between cotyledons
contributing to shoot development
Hypocotyl is portion below that contributes to
stem development
Radicle contributes to root development
Reproduction in
Plants
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Fruit Types and Seed Dispersal
Simple Fruits
Simple fruits are derived from single or several
united carpels
- Legumes are fruits that split along two sides when
mature
 Dehiscent
- Split open
 Indehiscent
- Fail to split open
Pea Flower and Pea Pod
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Reproduction in
Plants
Simple Fruits
Dry
Fleshy
Follicle
Drupe
Legume
Berry
Capsule
Pome
Achene
Nut
Grain
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Simple Fruits
Reproduction in
Plants
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Dispersal
- Many seeds are dispersed by wind
 Woolly
hairs, plumes, wings
Fleshy fruits - Attract animals and provide them
with food
- Peaches, cherries, tomatoes
Accessory fruit - Bulk of fruit is not from ovary, but
from receptacle
- Apples
Structure and Function of Fruits
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Compound Fruits
Reproduction in
Plants
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Compound fruits develop from several individual
ovaries
Aggregate Fruits
- Ovaries are from a single flower
- Blackberry
Multiple Fruits
- Ovaries are from separate flowers clustered
together
Seed Germination
Reproduction in
Plants
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When seed germination occurs, the embryo
resumes growth and metabolic activity
Length of time seeds retain their viability is quite
variable
Some seeds do not germinate until they have
been through a dormant period
- Temperate zones - Cold Weather
- Deserts - Rain
Seed Germination
Reproduction in
Plants
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Environmental requirements for seed germination
Availability of oxygen for metabolic needs
Adequate temperature for enzyme activity
Adequate moisture for hydration of cells
Light (in some cases)
Respiration and metabolism continue throughout
dormancy, but at a reduced level
Seed Structure and Germination
in the Common Garden Bean
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Corn Kernel Structure and Germination
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Reproduction in
Plants
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Asexual Reproduction in Plants
Plants contain nondifferentiated meristem tissue
Allows them to reproduce asexually by vegetative
propagation
Plant hormone auxin:
Can be used to cause roots to develop
Expands the list of plants that can be propagated
from cuttings
Asexual Reproduction in Plants
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Tissue Culture of Plants
Reproduction in
Plants
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Tissue culture is the growth of a tissue in an
artificial liquid or solid culture medium
Plant cells are totipotent
Meristem culture
Auxins and cytokinins allow many new shoots to
develop from a single shoot tip
- Virus-free clonal plants
Suspension Culture
Rapidly growing calluses are cut into small pieces
and shaken into a liquid nutrient medium
- Single cells or small clumps break off and form a
suspension
Tissue Culture in Plants
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Genetic Engineering
Reproduction in
Plants
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Traditionally, hybridization was used to produce
plants with desirable traits
 Crossing different varieties of plants
Transgenic plants can now be produced by
placing foreign genes into a plant
 Agricultural plants with improved traits
- Pest or insecticide resistant
 Commercial Products
- Human hormones, antibodies
Maize
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Genetically Engineered Plants
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Review
Reproductive Strategies
Alternation of generations
Adaptation to a land environment
Flowers
- Pollination
- Fertilization
Seed Development
Fruit
Seed Germination
Asexual Reproduction
Tissue Culture
Reproduction in
Plants
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Ending Slide Chapter 28
Reproduction in
Plants