Plant Response to StimuliMechanisms plants have to respond to environmental stimuli

How do plants respond to stimuli! They don’t get up and run away! They do:

Have tropisms in response to: Light, Gravity, Touch

Have defense against pathogens Have hormones that initiate signal

transduction pathways to send messages long-distance.

Responses to light Phytochromes:

Phototropism: Phytochromes can initiate hormones that

promote growth toward light (more later…) Circadium rhythm(daily)

4 o’clock flowers = to sleep cycle in animals Photoperiodism (seaonally)

Season for flowering: Short day plants vs. long day plants…when would

be the best time to flower in New England if…

Circadian Rhythm

Photoperiodism

Plant hormone experimental presentation! Find an experiment involving your plant

hormone: Introduction—What is your hormone used for? Hypothesis—What was the researchers

hypothesis? Methods—How did the researcher collect data. Data—Find a picture or graph to analyze

results and explain a verbal trend. Conclusion—What did the experimenters learn

about the plant hormones.

Hormones to be familiar with: Auxin Abscisic acid Cytokinins Ethylene Gibberellins