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Plant Reproduction

BI 103 Plant-Animal A&P

Turn in Homework #1

Bryophytes

Lycophytes

Green algae:

Chlorophytes

Gymnosperms Angiosperms

Pterophytes

Land plants

Vascular tissue

Seeds

Angiosperm specific adaptations

• Unlike other plants they have:

– Flowers

– Double fertilization

– Fruit

Why do plants have flowers? In other words, what are the advantages of flowering?

Discuss this question in groups

Angiosperms: the Flowering plants

Why do plants have flowers?

Enlists partnerships with insects and other animals

Less inbreeding

Higher probability the pollen will reach the right plant

They don’t have to produce as much pollen

Alternating Generations In more advanced plants, the sporophyte generation is

dominant.

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Alternation of generations modified

• Pollen= Male gametophyte

Contains sperm

• Ovule= Female gametophyte

Contains egg

How is pollen an adaptation to land?

Allows fertilization to occur even in the absence of available water.

Moss fertilization

Pollen grains

water

Anthers with microspores Microspore to pollen

1. The microspores divides by mitosis to produce two cells Generative cell (1n)

Tube cell== vegetative nucleus (1n)

2. A two layered wall develops around the microspore to become the pollen

3. The generative cell undergoes division once more 3n total (3 nuclei) in pollen

Double fertilization 1. Two pollen nuclei enter ovule

2. One fuses with the egg to form the zygote

3. The other fuses with 2 central cell nuclei to become the endosperm (3n), food for the zygote

Fruit development

Becomes the fruit! Becomes the seed!

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Why do we see such diversity in the flowers we see?

Theory: Coevolution of plants and pollinators Different flowers have evolved to attract different pollinators- plants have specialized to a specific group of pollinators

Pollination syndrome

Floral characteristics which attract a specific group of pollinator Bees, hummingbirds, moths etc

Allows flowers to specialize

May include mechanisms to exclude other pollinators

Pollination syndrome

What are the advantages to specializing to one species or one group of pollinator?

What are the disadvantage or risks?

Most flowers are ‘generalists’ and do not specialize.

Bees

Blue

Symmetrical

Smells sweet

Pollen

rewards

Nectar

rewards

Pheromone

rewards

Bees UV Markings

Bees can see in UV!

Pollinators: Bees Blue

UV marking

Symmetrical

Smells sweet

Nectar guides ---Example: Catalpa speciaosa

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Pedicularis attollens, common name:“Baby Elephant’s head”

Bumble bee pollinated

Specialized

Bee specialization

Pedicularis attollens

Buzz pollination

Technique only used by bees to release pollen from anthers– they must hit the right musical note!

Example: Tomatoes, blueberries, manzanita (Arctrostaphylos)

https://www.youtube.com/watch?v=Nv_xncrZfCg&feature=related

Birds: hummingbirds Red

Long and tubular

No odor

nectar

Moths

White flowers

Sweet smell

Open at night

Long nectar spur with nectar

Hawkmoth on Columbine (Aquileia)

Moths Darwin’s Orchid, Angraecum sesquipedale

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Why are those spurs so long?

Combination of:

Moths don’t want to get too close….

Predators lurk!

Plant needs moth to get close enough to reach pollen and stigma

Predator: Crab spider

Bats Strong pedicle and petals

Musky odor

White

Open at night & lots of pollen

Ex: Sargo cactus

Butterflies

Sweet smell

Vibrant colors

Larger flowers

Nectar rewards

Flies: rancid smell, tiny, green or reddish

Announcements

• Homework #2 Design a flower --Due next Monday 4/22

• Lab report– due Wed in lab

• Outdoor lab section?