Plantreproduction

Plant Reproduction

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Asexual Reproduction

• Asexual reproduction is natural “cloning.” Parts of the plant, such as leaves or stems, produce roots and become an independent plant.

• Talk about some benefits and some drawbacks to asexual reproduction.

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Sexual Reproduction

• Sexual reproduction requires fusion of male cells in the pollen grain with female cells in the ovule.

• Talk about some advantages and drawbacks to sexual reproduction.

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Terms to know:• Haploid: having a single set of

chromosomes in each cell.

• Diploid: having two sets of chromosomes in each cell.

• Mitosis: cell division, which produces two genetically identical cells.

• Meiosis: reduction division, which produces four haploid reproductive cells.

Angiosperms (flowering plants)• Plants that protect their seeds within the body

of a fruit.• Make up ¾’s of all plants, including:

– Trees, shrubs, herbs, grasses, water plants…

Structure of a Flower

Male Reproductive Structure

The stamen consists of two parts: Anther and Filament

The anther is where meiosis occurs to produce haploid pollen

The filament is a stalk that supports the anther

Female Reproductive StructureThe pistil consists of

the stigma, style and ovary

The sticky stigma receives the pollen from the anther

The pollen grows a tube down through the style

Meiosis occurs in the ovary to produce haploid ovules

Reproductive Structures

• Petals: colorful

structures that attract pollinators.

• Sepals: surround and protect the flower bud.

Pollination

Wind, insects or other animals transfer pollen from the anther of one flower to the stigma of another

Flowers vary depending on pollination mechanism

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Pollination is the transfer of pollen from the anther to the stigma

• This is an example of cross-pollination as the pollen travels from one flower to a different flower. This is desirable in plants as it promotes variation.

Flower Structure Pollination Fertilisation Seed Dispersal Germination Test

Click to view the animation

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Self-pollination occurs when pollen falls from the anther onto the stigma of the same flower

• Self-pollination is not desirable as it reduces variation

• Click to show animation of self-pollination

Flower Structure Pollination Fertilisation Seed Dispersal Germination Test

Pollination

Pollination VectorsWind Pollination: Dull, scentless flowers with reduced petalsBees/Butterfly Pollination: Bright

color, nectaries, scent. They sip nectar, get pollen on coats, transfer pollen from flower to flower

Bird Pollination: Nectaries, brightcolors, tube-like flowers

Moth Pollination: White petals, open at night

Fly Pollination:Rank odor, fleshcolored petals

• Pollen Grain • Anther Sac

Pollen grains contain two haploid cells produced through meiosis.1- The Tube cell – will grow the pollen tube. 2- The Generative cell – will go through mitosis to create two sperm cells.

OvaryEach ovule within an ovary has a micropyle (an opening for the pollen tube). The ovules’ megasporangium undergo meiosis to produce four haploid cells (3 die leaving 1 megaspore)The megaspore undergoes mitosis 3 times to produce 8 haploid cells within the embryo sac.

Fertilization

{ After pollen lands on the stigma, a pollen tube grows down through the style to ovary

{ Generative cell creates the two sperm nuclei

{ Double fertilization occurs: { one sperm fertilizes the egg{ one sperm the two polar nuclei together

Result of Double Fertilization

{ The sperm nucleus and egg nucleus join to form a 2n (diploid) embryo

{ The other sperm nucleus and the two polar nuclei join to form a 3n (triploid) endosperm. The endosperm is the food supply for the embryo.

{ First link

Seed and Fruit Development

{ After fertilization, the petals and sepals fall off flower

{ Ovary “ripens” into a fruit

{ The ovule develops into a seed

Seed Dispersal Mechanisms-Allow plants to colonize new areas and avoid

shade of parent plant

Wind Dispersal - Flight mechanisms, like parachutes, wings, etc. Ex. Dandelion, maples, birch

Animal Dispersal - Fleshy fruits which animals eat, drop undigested seeds in feces or burrs which stick to animals’ coats

Gravity Dispersal - Heavy nuts fall to ground and rollex. acorns

Water Dispersal - Plantsnear water create floating fruitsex. coconuts