Introduction to Plant Reproduction

23.1

Reproduction

Sexual reproduction

–Joining of an egg and sperm

Asexual reproduction

–A single organism replicating its genetic material to split into two identical organisms.

Vegitative Reproduction A form of asexual reproduction where

a new plant grows from parts of an existing plant.

Fast reproduction Examples:

– Strawberry runners– Moss fragmentation– Potato eyes and buds

Alteration of Generations

Alteration of GenerationsOf Nonseed Nonvascular Plants

Alteration of GenerationsOf Nonseed Vascular Plants

Alteration of GenerationsOf Naked Seed Vascular Plants

Alteration of GenerationsOf Flowering Seed Vascular Plants

Alteration of Generations

Fertilization: Nonvascular plants- Need a film of

water for the sperm to reach the egg.

Vascular plants- Do not need water for the sperm to reach the egg.

Alteration of Generations

As plants evolved, the sporophyte generation became larger:

Nonvascular plants- Sporophyte depends on the gametophyte for support and nutrition.

Vascular plants- Sporophyte lives independent of the gametophyte.

Moss reproductive cycle Gametophyte dominant

– Male= Antheridium

– Female= Archegonium

ArchegoniumAntheridium

Moss reproductive cycle Antheridium- Male produces

flagellated sperm that need water to get to the archegonium.

Chemotaxis- Female archegonium produces chemicals that attract/direct the sperm.

Moss reproductive cycle

Moss reproductive cycle Sporophyte- Depends on the

gametophyte for support and

nutrition. Protonema- Spores that land in a

favorable spot develop into a protonema (gametophyte

generation).

Fern reproductive cycle Sporophyte dominant Frond- feathery stems of a fern Sorus- underneath the frond

–Produces spores

Fern reproductive cycle Prothallus

– The fern spore grows into a prothallus when it lands on damp, rich soil.

– Heart shaped

– Contains Antheridia

& Archegonium

Conifer reproductive cycle

Sporophyte dominant Heterosporous- Produces two kinds

of spores that develop into male and female cones.

– Female cones

–Made of many scales

–2 ovules at the base of each scale

–Each ovule produces a Megaspore which develops into the female archegonia.

Conifer reproductive cycle

– Male cones

–Made of small scales that form microspores

–4 microspores develop into a single pollen grain

–Pollen grains are the

male gametophyte that

are transported on air

currents

Chapter 23.2

Flowers

The Parts of a Flower

• Most flowers have four parts:

• sepals,• petals,• stamens,• Carpels (pistils)

The parts of a flower• Sepals protect the

bud until it opens.• Petals attract

insects.• Stamens make

pollen.• Pistils (carpel)

grow into fruits which contain the seeds.

Stamen (male)

• Anther: pollen grains grow in the anther.

• When the grains are fully grown, the anther splits open.

• Filament: holds the anther

Pistil (female)

• Stigma• Style• Ovary

Stigma – sticky place for pollen to attachStyle – where pollen nuclei travels to reach the eggOvary – where egg is located

Modifications in Flowers Complete flowers – have all four

organs (sepals, petals, stamens, and pistils)– M orning glory and tiger lily

Incomplete flowers – lacks one or more of the four organs– Squash and corn

Tiger Lily – a complete flower

Female Squash Flower Male Squash Flower

Incomplete Flowers

Modifications in Flowers P erfect flowers- Have both stamens

and pistils (E x: Lily) Imperfect flowers- E ither have a

functioning stamen or pistil, but not bothE x : Cucumber, Squash

Pollination Mechanisms Animal pollination

– hummingbirds & bees transfer pollen from plant to plant

– Flowers are brightly colored or highly scented

Wind pollination– lightweight and are carried by wind– Small flowers with little color or scent

Self pollination– Able to pollinate flowers on same plant– Have both pistel and stamen

Pollinators

PHOTOPERIODICITY Plants flower based

on the number of hours of darkness they are exposed to

Short-day plants -

flower when days are short (fall, winter, spring)

Ex: Pansy,

Poinsettias

PHOTOPERIODICITY Long-day plants -

flower when days are long (summer)

Examples:

– Potatoes

– Clover

– Spinach

PHOTOPERIODICITY Intermediate-day

plants- Grow when darkness is about equal to daylight.E x : Sugar Cane

PHOTOPERIODICITY Day-neutral plants-

Hours of darkness does not effect flowering, as long as there is enough daylight to perform photosynthesis.

E x: Corn, tomatoes, cotton, roses

Chapter 23.3

Flowering P lants

Flowering Plant reproductive cycle

Sporophyte dominant Ovary- produces 4 megaspores, but 3

disintegrate and only one remains. Double fertilization – requires 2 sperm

to fertilize the egg and make a seed. Seed – embryo (cotyledons),

endosperm (food for embryo), seed coat (protect seed)

Flowering Plant Reproduction

4 kinds of fruit

1. Simple Fleshy fruits- contain one or more seeds.

Ex: Apples, Peach, grape, tomato, pumpkin

4 Kinds of fruit

2. Aggregate fruit- Most berries. Many female parts fuse to form one fruit.

Ex: Blackberries, strawberries, raspberries

4 Kinds of fruit

3. Multiple fruit- Flowers fuse to form one fruit.

Ex: Pineapples, figs

4 Kinds of fruit

4.. Dry fruit- Fruits that are dry.

Ex: Nuts, grains, seed pods

Seed Dispersal Water

– Coconuts Wind

– Dandelions Animals

– Fruits attract animals that will eat the seeds so that the seeds can be carried far away where it won’t have to compete with its parent.

Seed Germination Requires:

– Water (swells and breaks seed coat)– Oxygen (cell respiration as seed grows)– Optimal Temperature (each plant requires

a certain temperature to begin growth)

Seeds will lie dormant in their hard seed coats waiting for optimal conditions.