Ch. 22.2 – 22.5 Flowering plant reproduction, germination, dispersal, and hormone response

Flower reproduction Sepals: modified leaves that protect the developing flower (outer most layer) Petals: layer just inside sepals. Brightly colored to attract pollinators Stamen: male reproductive structure made up of anthers and filament Carpel: female reproductive structure made up of stigma, style, and ovary

Pollinators: Flower can be pollinated by wind or animals

Pollination and fertilization Pollination: pollen grain sticks to the stigma Double fertilization: after pollination, pollen grain grows a pollen tube to the ovule. Two sperm cells travel down the pollen tube. One sperm fertilizes the egg one sperm: combines with the polar nuclei in the embryo sac. This cell is now triploid ( 3n) Endosperm: 3n nucleus will become the endosperm (food supply for embryo) Double fertilization: process of one sperm fertilizing an egg and the other forming a triploid cell

Fruit After fertilization: ovule become the seed While seed develops, ovary grows into a fruit

Seed dispersal and germination Animals, wind, and water can spread seeds Seeds can stay dormant for long periods of time and then grow when conditions are favorable 2000 year old date palm seed found, planted, and grown Germination: embryo begins to grow into seedling

Asexual reproduction Regeneration: process by which some plants grow a new individual from a fragment of stem, leaf, or root Vegetative reproduction: asexual reproduction in which a stem, leaf, or root attached to a parent plant grows a new individual

Types of asexual reproduction Plant structures that are specifically adapted for vegetative reproduction Stolons: horizontal stems (runners) that take root and grow into a new plant Rhizomes: underground horizontal runners that grow into a new plant Tubers: an underground stem modified for storage. They produce buds that can sprout a new plant….. potatoes Bulbs: underground stems which are surrounded by modified leaves adapted for storage and covered with a protective skin. Under favorable conditions, will grow into a new plant

Plant hormones Hormones: chemical messengers produced in one area of an organism that stimulates or suppresses activity of cells in another area.

Plant hormones Gibberellins: hormone that produces dramatic increase in size involved in ending seed dormancy, germination, rapid growth of young seedlings, and large size of fruits - Used by growers to help plants produce longer stems and bigger fruit

Plant hormones Ethylene: plant hormone that causes ripening and is naturally occurring in fruits growers use ethylene to their advantage: filter it out to cause a delay in ripening or gas to artificially ripen

Plant hormones Cytokinins: plant hormone that stimulates cytokinesis (division of the cytoplasm). Final stage of cell division. Produced in growing roots, developing seeds, and fruit. Associated with lateral growth. - Used to slow aging process of some plant organs… floral leaves

Plant hormones Auxins: plant hormone involved in the lengthening of cells produced in the apical meristem (growing tip). Stimulates the growth of primary stems. - used by growers to control growth by removing growing tips from plants High concentrations prevents plant growth (especially in roots) Used in many herbicides to kill unwanted plants Build up of auxins on the shaded side of a stem causes it to bend toward the light… phototropism Tropism: movement of a plant in response to an environmental stimulus