Plant Reproduction and Responses I.Plant responses A. Phototropism B. Gravitropism C. Thigmotropism II.Photoperiodism A. Short day plants B. Long day plants C. How adaptation? III.Reproduction A. Pollen carried by B. Ex. Of fruits C. germination

PLANT RESPONSES AND REPRODUCTION

Plant responses (tropisms): Phototropism: growth of a plant towards light Gravitropism: plant growth in response to gravity Thigmotropism: growth response to touch Photoperiodism: response to daylight-darkness conditions

Section 24.2 Summary – pages Photoperiodism Plant biologists originally thought that the length of daylight controlled flowering. However, they now know that it is the length of darkness that controls flowering, and that the darkness must be uninterrupted.

Section 24.2 Summary – pages Photoperiodism Plants are short-day plants, long-day plants, day-neutral plants, or intermediate day plants. A short-day plant flowers when the number of daylight hours is shorter than that of its critical period.

Section 24.2 Summary – pages Photoperiodism Short-day plants usually flower sometime during late summer, fall, winter, or spring.

Section 24.2 Summary – pages Photoperiodism A long-day plant flowers when the number of daylight hours is longer than that of its critical period. Long-day plants usually flower in summer, but also will flower if lighted continually.

Section 24.2 Summary – pages Photoperiodism Some plants will flower over a range in the number of day-light hours. These plants are called day-neutral plants. An intermediate-day plant will not flower if days are shorter or longer than its critical period.

Section 24.2 Summary – pages Photoperiodism Photoperiodism is an adaptation that ensures the production of flowers at a time when there is an abundant population of pollinators.

PLANT REPRODUCTION Pollen is produced by the stamen. Pollen is carried by wind or animals to another plant. Pollen fertilizes the egg in the ovary at the base of the pistil.

The ovary develops into a fruit that encloses the seeds. Fruits are dispersed with wind or animals. Fruits are not always edible, anything with a seed inside is a fruit. (helicopters, acorns, dandelions)

ASEXUAL REPRODUCTION Many plants can clone themselves (called vegetative propagation) Strawberry plants send out runners which grow into new plants. Some plant clippings will grow into new plants.

HOW PLANTS GROW Germination occurs when a seed sprouts (needs moisture and light)

Perennials: live several years and reproduce many times ex. roses, trees, shasta daisy Annuals: lives one growing season (grows, flowers, reproduces, dies) ex. pansy, sunflower Biennials: takes two growing seasons to complete, reproduces in the 2 nd season

Section 24.1 Summary – pages Click image to view movie. Life Cycle of Ferns

Section 24.1 Summary – pages The Life Cycle of Conifers Click image to view movie.

Section 24.3 Summary – pages Seed formation Click image to view movie.

Section 24.3 Summary – pages Fruit formation Click image to view movie.