Angiosperm Reproduction

What you need to know: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 Angiosperms have 3 unique Features:eatures:

1.1. FFlowers2.2. FFruits3. double FFertilization

Alternation of GenerationsAlternation of Generations

1. Sporophyte (mature plant) produces spores

2. Spores develop into male (♂) gametophyte (pollen) and female (♀) gametophyte (embryo sac)

Flower StructureFlower StructureReproductive shoots of angiosperm

sporophyteFlower organs:

1. Sepal – leaflike, protect flower bud2. Petal – modified leaves, attract pollinators3. Stamen – ♂ reproductive organ

anther + filament

4. Carpel – ♀ reproductive organ stigma + style + ovary

Flower attached to stem at receptaclePollination by wind, insects, birds

Floral VariationsFloral VariationsComplete: has petals, sepals, stamen, carpelsIncomplete: lacks 1+ of the abovePerfect: has both stamen + carpelImperfect: 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 GametophyteFemale

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 FertilizationDouble 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 embryoThe development of a plant embryo

FruitFruitProtects enclosed seed(s)Aids in dispersal by water, wind,

or animals

Simple Aggregate Multiple

Single ovary of one flower

Many ovaries of one flower

Many ovaries of

many flowers

Cherry Raspberry Pineapple

SeedsSeeds

Adaptations:1.Dormancy = “resting”

Low metabolic rate, not growing or developing

Increases chances of germination in most advantageous time & place

2.Dispersal: variety of methods3.Protection: well protected by fruit

GerminationGerminationImbibition: 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

GerminationGermination

1. Radicle Root2. 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

Sexual AsexualBoth ways to reproduce

Flower seedsRunners, 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

Plant ReproductionPlant Reproduction