Sexual Reproduction In Plants Meeting the Challenge

Making New Plants Many plants reproduce successfully through assexual reproduction. Many plants reproduce successfully through assexual reproduction. Others use sexual reproduction to pass on their genetic material. Others use sexual reproduction to pass on their genetic material. This is challenging because most plants do not move. This is challenging because most plants do not move.

Meeting the Challenge In animals the product of sexual reproduction is the zygote. In animals the product of sexual reproduction is the zygote. In plants the product of sexual reproduction is the seed. In plants the product of sexual reproduction is the seed. The seed contains an embryo, a food supply and a seed coat (protects seed from dehydration). The seed contains an embryo, a food supply and a seed coat (protects seed from dehydration). Plants can be classified into two groups based on their seed type. Plants can be classified into two groups based on their seed type.

Angiosperms Flowering plants Flowering plants The seeds form inside the flowers. The seeds form inside the flowers. When mature the seeds are enclosed in a case, such as a pod or a shell. When mature the seeds are enclosed in a case, 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 angiosperms Can you name other angiosperms

Gymnosperms Gymnosperms do not produce flowers. Gymnosperms do not produce flowers. Seeds are produced inside cones. Seeds are produced inside cones. Their seeds have a coat but they are not enclosed in a case. Their seeds have a coat but they are not 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 ?? Not all plants fall into these two categories. Not all plants fall into these two categories. Ferns and mosses are neither angiospem nor gymnosperm. Ferns and mosses are neither angiospem nor gymnosperm. They reproduce sexually without seeds. They reproduce sexually without seeds. Look on Page 60 - which do not produce seeds. Look on Page 60 - which do not produce seeds.

Sexual Reproduction in Angiosperms More than one half of all known plants are angiosperms. More than one half of all known plants are angiosperms. Some produce large, showy flowers (lily, tulip,etc,) Some produce large, showy flowers (lily, tulip,etc,) Some have very small, easily missed flowers (grasses) Some have very small, easily missed flowers (grasses) Bif or small, all flowers have the same function. Bif or small, all flowers have the same function.

Purpose of Flowers All of the plant’s reproductive organs are contained in the flower. All of the plant’s reproductive organs are contained in the flower. Female reproductive organ is called the pistil. Female reproductive organ is called the pistil. Male reproductive organ is called the stamen Male reproductive organ is called the stamen

Reproductive Organs In Angiosperms

Pollination and Fertilization in Angiosperms Before seeds can develop inside the flower pollen grains from the anther must reach the stigma of the pistil. Before seeds can develop inside the flower pollen grains from the anther must reach the stigma of the pistil. Some plants self-pollinate - both male and female gametes come from the same plant. Some plants self-pollinate - both male and female gametes come from the same plant. What might be some of the advantages to this type of sexual reproduction? What might be some of the advantages to this type of sexual reproduction?

Pollination and Fertilization in Angiosperms Most angiosperms cross-pollinate. Most angiosperms cross-pollinate. Pollen from one plant is transferred to another plant. Pollen from one plant is transferred to another plant. Most common way to cross pollinate is to use the wind or insects. Most common way to cross pollinate is to use the wind or insects. Which type of pollination would produce the most seeds? Which type of pollination would produce the most seeds?

Development of a Pollen Tube

Seed Development in Angiosperms While pollen tube is growing, cells inside ovule prepare for its arrival. While pollen tube is growing, cells inside ovule prepare for its arrival. Once the sperm cell meetws the egg, a zygote is formed. Once the sperm cell meetws the egg, a zygote is formed. Other cells in the ovule develop into the cotyledon which contains food. Other cells in the ovule develop into the cotyledon which contains food. Zygote now goes through mitosis to form an embryo. Zygote now goes through mitosis to form an embryo.

In Angiosperm the developing seed is surrounded by the walls of the ovary. In Angiosperm the developing seed is 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 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 from the parent. Dispersal is the transport of the seed away from the parent. Some launch their own fruits Some launch their own fruits Some need help from outside agents Some need help from outside agents Wind, animals, water Wind, animals, water

Germination and Growth Germination - the process in which a seed begins to grow, Germination - the process in which a seed 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 of a bean plant. Look at page 68 in text to see the germination 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 Gymnosperms 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 conifers. These plants are called conifers. Usually male and female cones are produced in the same trees. Usually male and female cones are produced in the same trees. Seeds contain an embryo, food supply, and a coat - but no fruit. Seeds contain an embryo, food supply, and a coat - but no fruit.