Transcript Warm-Up - sandsbiochem

Chapter 38
Angiosperm Reproduction
What you need to know:
The relationship between seed and fruit.
 How temperature and moisture
determine seed germination.
 How different modes of plant
reproduction affect their genetic diversity.
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Angiosperms have 3 unique Features:
1.
2.
3.
Flowers
Fruits
Double Fertilization
SYMMETRY
OVARY LOCATION
FLORAL DISTRIBUTION
Bilateral symmetry
(orchid)
Lupine inflorescence
Superior
ovary
Radial symmetry
(daffodil)
Sepal
Fused petals
Semi-inferior
ovary
Inferior
ovary
Sunflower
inflorescence
REPRODUCTIVE VARIATIONS
Maize, a monoecious species
Dioecious Sagittaria latifolia (common
arrowhead)
Pollination: transfer pollen from anther to stigma
 Pollen tube grows down into ovary for 2 sperm to
travel to egg

Some plants are self-pollinated
 Cross-pollinated plants:
◦ Self-incompatibility: plant rejects own pollen or
closely related plant
◦ Maximize genetic variation

Stigma
Stigma
Anther
with
pollen
Pin flower
Thrum flower
“Pin” and “thrum” flower types reduce self-fertilization
The development of a plant embryo
Fruit
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Egg cell  plant embryo
Ovules inside ovary  seeds
Ripe ovary  fruit
Fruit protects enclosed seed(s)
Aids in dispersal by water, wind, or animals
Types of Fruit
Seeds
Mature seed  dormancy (resting)
 Low metabolic rate
 Growth & development suspended
 Resumes growth when environmental
conditions suitable for germination
Seed
Structure
Germination

Seed take up water (imbibition)  trigger
metabolic changes to begin growth
1. Root develops
2. Shoot tip emerges above ground
 Stimulated by light
3. Foliage leaves expand & turn green 
photosynthesis

Very hazardous for plants due to vulnerability
 Predators, parasites, wind
Seed
Germination
Plant Reproduction
Sexual
Asexual
(Vegetative Reproduction)
Flower  Seeds
Runners, bulbs, grafts, cuttings
vegetative (grass), fragmentation,
test-tube cloning
Genetic diversity
Clones
More complex & hazardous for
seedlings
Simpler (no pollinator needed)
Advantage in unstable
environments
Suited for stable environments
Asexual reproduction in aspen trees
Test-tube cloning of carrots
Just a few parenchyma
cells from a carrot gave
rise to this callus, a mass
of undifferentiated cells.
The callus differentiates
into an entire plant, with
leaves, stems, and roots.
Humans Modify Crops
Artificial selection of plants for breeding
 Plant Biotechnology:
◦ Genetically modified organisms
 “Golden Rice”: engineered to produce betacarotene (Vit. A)
 Bt corn: transgenic – expresses Bt (bacteria)
gene  produces protein toxic to insects
◦ Biofuels – reduce CO2 emissions
 Biodiesel: vegetable oils
 Bioethanol: convert cellulose into ethanol
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