Plants Part 7 Reproduction Asexual Reproduction Plants use

Plants Part 7: Reproduction

Asexual Reproduction • Plants use many structures to reproduce asexually. – Rhizomes are modified stems such as stolons, eyes on tubers, etc. – Modified leaves or shoots that can grow into new plants • Usually occurs by the mitosis of diploid cells • Makes genetically identical individuals (clones)

Asexual Benefits: • If plant is successful in its environment, all offspring will get the same traits. • Plant does not need reproductive structures, which require a lot of energy • Only one plant needed • Higher survival rate

Asexual Cost: • Environment selects only individuals with traits that are favoured. • Lack of variation can be dangerous for survival in environments that are not ideal.

Human Use of Asexual Reproduction • Clone desirable plants by: – Stem cutting and place in water and once the roots grow, transfer to the soil – Grafting: cut a young branch of one plant and attach it to the stem of another plant of same or similar species

Seed Plant Sexual Reproduction • Seed functions: protect and nourish the embryo and carry it to a new location. • Seed dispersal by: – Wind – Animals eating fruit – Animals spreading from fur • Increases chance of survival

Seed Anatomy • Monocots have one cotyledon with endosperm that feeds embryo. • Dicots have two cotyledons that feed the embryo.

Gymnosperm Sexual Reproduction • Conifers produce both male cones and female cones. • Haploid cells called microspores are made in meiosis in the male cones that develops into a pollen grain containing the male gametophyte. • Meiosis in female cones make megaspores that make eggproducing female gametophytes.

Seed Pollination and Fertilization • Pollen grains have to move from the male cone to the female cone by pollination via the wind. • The pollen grain grows a pollen tube that grows down to the ovule and releases two sperm nuclei. – One fertilizes the egg, the other degrades – Takes 13 months for the egg to be fertilized. • Ovule then develops into a zygote, then an embryo. • If the seed germinates, it becomes a sporophyte.

Sexual Reproduction in Angiosperms • The products are seeds inside of a fruit • Fruit is a mature ovary • Flowers are the key organs in sexual reproduction • Animal pollinated flowers are usually dramatic in order to attract bees, birds, insects. • Cross pollination is when pollen is transferred from one plant to another. • Self pollination is when pollen goes from one flower to another flower on the same plant.

Flower Anatomy CARPEL

Angiosperm Life Cycle