Plant Responses to Internal and External Signals

Page
11

stimulus

Relay proteins and

second messengers

Activation

of cellular

responses

1

2

3

Slide 76

Review

Photoreversible states of phytochrome

Pr

Pfr

Red light

Far-red

light

Responses

Slide 77

You should now be able to:

Compare the growth of a plant in darkness (etiolation) to the characteristics of greening (de-etiolation).

List six classes of plant hormones and describe their major functions.

Describe the phenomenon of phytochrome photoreversibility and explain its role in light-induced germination of lettuce seeds.

Explain how light entrains biological clocks.

Slide 78

Distinguish between short-day, long-day, and day-neutral plants; explain why the names are misleading.

Distinguish between gravitropism, thigmotropism, and thigmomorphogenesis.

Describe the challenges posed by, and the responses of plants to, drought, flooding, salt stress, heat stress, and cold stress.