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Angiosperm Reproduction
What you need to know:
The process of double fertilization, a
unique feature of angiosperms.
 The relationship between seed and fruit.
 The structure and function of all parts of
the flower.

Angiosperms have 3 unique Features:
1.
2.
3.
Flowers
Fruits
double Fertilization
Alternation of Generations
1.
2.
Sporophyte (mature plant) produces
spores
Spores develop into male (♂)
gametophyte (pollen) and female (♀)
gametophyte (embryo sac)
Flower Structure
Reproductive shoots of angiosperm sporophyte
 Flower organs:
1. Sepal – leaflike, protect flower bud
2. Petal – modified leaves, attract pollinators
3. Stamen – ♂ reproductive organ


anther + filament
4. Carpel – ♀ reproductive organ

stigma + style + ovary
Flower attached to stem at receptacle
 Pollination by wind, insects, birds

Floral Variations






Complete: has petals, sepals, stamen, carpels
Incomplete: lacks 1+ of the above
Perfect: has both stamen + carpel
Imperfect: has stamen or carpel, not both (grass no petals)
Monoecious: plant species w/ both staminate and
carpellate flowers on the same individual (corn)
Dioecious: plant species w/ staminate flowers and
carpellate flowers on different individual plants
(date palm, arrowhead)
Male Gametophyte
Female Gametophyte
= Pollen Sac
= Embryo Sac
Produced in anther
Produced in ovule (in ovary)
Has 2 haploid nuclei:
1. Tube nucleus (forms pollen
tube)
2. Generative nucleus (divides to
form 2 sperm cells)
Has 3 important haploid nuclei:
1. Egg (fuses with sperm)
2. 2 polar nuclei (fuses with 2nd
sperm to make 3n endosperm)
Pollination: transfer pollen from anther to
stigma
 Pollen tube grows down into ovary

Double Fertilization
Union of 2 sperm cells with different cells of
embryo sac
1. One sperm + egg  zygote (2n)
2. One sperm + 2 polar bodies  endosperm
(triploid 3n)

◦
Endosperm = nutrition for embryo plant
3. Ovule
develops into seed; ovary develops
into fruit
◦
Seed = embryo + endosperm
The development of a plant embryo
Fruit
Protects enclosed seed(s)
 Aids in dispersal by water, wind, or
animals

Simple
Aggregate
Multiple
Many ovaries
Single ovary Many ovaries
of many
of one flower of one flower
flowers
Cherry
Raspberry
Pineapple
Developmental origins of fruit
Seeds
Adaptations:
1. Dormancy = “resting”


Low metabolic rate, not growing or developing
Increases chances of germination in most
advantageous time & place
2. Dispersal: variety
of methods
3. Protection: well protected by fruit
Seed
Structure
Germination

Imbibition: uptake of H2O
◦ Seed expands and seed coat ruptures
◦ Trigger metabolic changes to begin growth
◦ Enzymes digest storage materials of
endosperm (cotyledons)
◦ Nutrients transferred to growth regions of
embryo
Germination
Radicle  Root
Shoot tip emerges above ground
1.
2.

Stimulated by light
3.
Foliage leaves expand & turn green 
photosynthesis

Very hazardous for plants due to
vulnerability
◦
Predators, parasites, wind
Dicot and
Monocot
Seed
Germination
Plant Reproduction
Sexual
Asexual
Both ways to reproduce
Flower  seeds
Runners, bulb, root, graft,
vegetative (grass), fragmentation
Genetic diversity
Clone
More complex & hazardous for
plant
Simpler & safer for plant
• Monoculture - cultivate w/ 1
plant
• Reduces competition
• Benefits farmers