Sexual Reproduction In Plants Meeting the Challenge.

Sexual Reproduction In Sexual Reproduction In PlantsPlants

Meeting the ChallengeMeeting the Challenge

Making New PlantsMaking New Plants

Many plants reproduce successfully through Many plants reproduce successfully through assexual reproduction.assexual reproduction.

Others use sexual reproduction to pass on their Others use sexual reproduction to pass on their genetic material.genetic material.

This is challenging because most plants do not This is challenging because most plants do not move.move.

Meeting the ChallengeMeeting the Challenge

In animals the product of sexual reproduction is the In animals the product of sexual reproduction is the zygote.zygote.

In plants the product of sexual reproduction is the In plants the product of sexual reproduction is the seed.seed.

The seed contains an embryo, a food supply and a The seed contains an embryo, a food supply and a seed coat (protects seed from dehydration).seed coat (protects seed from dehydration).

Plants can be classified into two groups based on Plants can be classified into two groups based on their seed type.their seed type.

AngiospermsAngiosperms

Flowering plantsFlowering plants The seeds form inside the flowers.The seeds form inside the flowers. When mature the seeds are enclosed in a case, When mature the seeds are enclosed in a case,

such as a pod or a shell.such as a pod or a shell. Look at page 60 - which are angiosperms?Look at page 60 - which are angiosperms? Can you name other angiospermsCan you name other angiosperms

GymnospermsGymnosperms

Gymnosperms do not produce flowers.Gymnosperms do not produce flowers. Seeds are produced inside Seeds are produced inside conescones.. Their seeds have a coat but they are not Their seeds have a coat but they are not

enclosed in a case.enclosed in a case. Look at page 60 - which are gymnosperms?Look at page 60 - which are gymnosperms? Can you name other gymnosperms?Can you name other gymnosperms?

Others ??Others ??

Not all plants fall into these two categories.Not all plants fall into these two categories. Ferns and mosses are neither angiospem nor Ferns and mosses are neither angiospem nor

gymnosperm.gymnosperm. They reproduce sexually without seeds.They reproduce sexually without seeds. Look on Page 60 - which do not produce Look on Page 60 - which do not produce

seeds.seeds.

Sexual Reproduction in Sexual Reproduction in AngiospermsAngiosperms

More than one half of all known plants are More than one half of all known plants are angiosperms.angiosperms.

Some produce large, showy flowers (lily, Some produce large, showy flowers (lily, tulip,etc,)tulip,etc,)

Some have very small, easily missed flowers Some have very small, easily missed flowers (grasses)(grasses)

Bif or small, all flowers have the same Bif or small, all flowers have the same function.function.

Purpose of FlowersPurpose of Flowers

All of the plant’s reproductive organs are All of the plant’s reproductive organs are contained in the flower.contained in the flower.

Female reproductive organ is called the Female reproductive organ is called the pistil.pistil. Male reproductive organ is called theMale reproductive organ is called the stamen stamen

Reproductive Organs In AngiospermsReproductive Organs In Angiosperms

Pollination and Fertilization in Pollination and Fertilization in AngiospermsAngiosperms

Before seeds can develop inside the flower Before seeds can develop inside the flower pollen grains from the anther must reach the pollen grains from the anther must reach the stigma of the pistil.stigma of the pistil.

Some plants self-pollinate - both male and Some plants self-pollinate - both male and female gametes come from the same plant.female gametes come from the same plant.

What might be some of the advantages to this What might be some of the advantages to this type of sexual reproduction?type of sexual reproduction?

Pollination and Fertilization in Pollination and Fertilization in AngiospermsAngiosperms

Most angiosperms cross-pollinate.Most angiosperms cross-pollinate. Pollen from one plant is transferred to another Pollen from one plant is transferred to another

plant.plant. Most common way to cross pollinate is to use Most common way to cross pollinate is to use

the wind or insects.the wind or insects. Which type of pollination would produce the Which type of pollination would produce the

most seeds?most seeds?

Development of a Pollen TubeDevelopment of a Pollen Tube

Seed Development in Seed Development in AngiospermsAngiosperms

While pollen tube is growing, cells inside While pollen tube is growing, cells inside ovule prepare for its arrival.ovule prepare for its arrival.

Once the sperm cell meetws the egg, a zygote Once the sperm cell meetws the egg, a zygote is formed.is formed.

Other cells in the ovule develop into the Other cells in the ovule develop into the cotyledon which contains food.cotyledon which contains food.

Zygote now goes through mitosis to form an Zygote now goes through mitosis to form an embryo.embryo.

In Angiosperm the developing seed is In Angiosperm the developing seed is surrounded by the walls of the ovary.surrounded by the walls of the ovary.

As the ovary matures it becomes the fruit.As the ovary matures it becomes the fruit.

Seed Dispersal in AngiospermsSeed Dispersal in Angiosperms

The fruit of an angiospern aids in its dispersal.The fruit of an angiospern aids in its dispersal. Dispersal is the transport of the seed away Dispersal is the transport of the seed away

from the parent.from the parent. Some launch their own fruitsSome launch their own fruits Some need help from outside agentsSome need help from outside agents

Wind, animals, waterWind, animals, water

Germination and GrowthGermination and Growth

Germination - the process in which a seed Germination - the process in which a seed begins to grow,begins to grow,

Some seeds can lay dormant for years.Some seeds can lay dormant for years. Look at page 68 in text to see the germination Look at page 68 in text to see the germination

of a bean plant. of a bean plant. What process is going on at the cellular level?What process is going on at the cellular level?

Sexual Reproduction of Sexual Reproduction of GymnospermsGymnosperms

The life cycle is similar to angiosperms.The life cycle is similar to angiosperms. Gymnosperms do not bear flowers.Gymnosperms do not bear flowers. These plants are called These plants are called conifers.conifers. UsuallyUsually male and female cones are produced male and female cones are produced

in the same trees.in the same trees. Seeds contain an embryo, food supply, and a Seeds contain an embryo, food supply, and a

coat - but no fruit.coat - but no fruit.