Sexual Reproduction includes: • Pollination • Fertilization • Seed Production • Sexual reproduction also known as seed reproduction because it involves using seeds to produce new plants.
Seeds • Seeds contain all the genetic characteristics of the parent plant • However, the characteristics of the plant grown from seeds may vary from parent plant.
Reasons for Seed Propagation Most Economical Allows a grower to produce a larger number of plants. Most widely used method
Parts of the Flower • Pistil – Female reproductive part of the flower • Stigma- Sticky surface to capture the pollen • Style- Tube that connects the stigma to the ovary • Ovary-contains the ovules. • Stamen- Male reproductive part of the flower • Anther- produces the pollen grains • Filament- supports the anther.
Pollination • When a flower opens, the stamens mature and become fully developed. • The anthers on the stamen then release hundreds of pollen grains • Pollen grains are the male sex cell • Each pollen grain contains genetic characteristics of the plant.
Pollination • Flower ovary contains one or more ovules, which are the female sex cells • Each ovule contains genetic information of the plant as well. • Pollination occurs when the pollen grains come into contact with the sticky surface of the stigma.
Types of Pollination • Self Pollination: • The transfer of pollen from the anther of a flower to the stigma of the same flower., or to a different flower on the same plant. • Cross Pollination • The transfer of pollen from the anther of a flower to the stigma of a flower on a different plant.
Self Pollination • More Effective • Almost guarantees pollination • Isn't’ dependable on outside variables for pollination
Cross Pollination • Increases genetic variability • Accomplished through • Wind • Bees • Birds
Methods of Pollen Distribution • Wind • Pollen grains are carried by wind from one flower to another • Animals • Birds ( Hummingbirds) • Insects ( moths, butterflies, bees, flies) • Mammals ( bats)
Flowers of wind pollinated plants are: • Small • Greenish or brown • No fragrance • Small or no petals • No Nectar Examples Include Grasses, wheat and cattails
Flowers that are pollinated by hummingbirds and butterflies are: • Tube shaped • Fragrant fro butterflies, no fragrance for hummingbirds • Brightly colored, usually red attracts hummingbirds • Produce nectar which is an attractive snack.
Flowers that are pollinated by flies • Brown and dark colored • Have foul odor
Flowers that are pollinated by bees are • Fragrant (nectar as a “reward) • Brightly colored with nectar guides visibly only with UV light that bees can see, which directs bees to the center of the flower • Sweet Fragrance • Produce Nectar
Flowers that are pollinated by bats and moths • Tube Shaped • Fragrant • White or yellow which can be seen easily at night • Sometimes only open at night
Fertilization • Cells of many plant flowers are diploid ( two sets of chromosomes) Represented by 2n • Some of these cells undergo a process of cell division called meiosis. This process causes the chromosomes number to be halved and the result are “daughter cells”. • The daughter cells are haploid (one set of chromosomes) represented by 1n
Fertilization • The daughter cells undergo another process of cell division called mitosis, which produce more haploid egg or sperm cells. • When these cells come together (fertilization) they form the zygote which is then a diploid
Process of fertilization • After the pollen grain lands on the stigma, it develops a pollen tube which travels down the style. • The pollen grain releases a sperm cell, in some cases 2 sperm cells • The sperm travel down the pollen tube and reach the ovary, then enter the ovule • If there are two sperm cells, one fertilizes the egg while the other fuses with another cell and produces the endosperm. This is called double fertilization.
Development of Seed • The diploid zygote forms the embryo. These cells will later divide and form parts of the seed • Cells in the outer layer of the ovule harden and become the seed coat. • The endosperm grows and becomes the food source for the growing seed
3 essential parts of the seed. • Embryo- Embryonic Root (Radical) • Endosperm/Cotyledon- Food Reserve • Seed Coat