Plant Signaling and Response Hormones Review chemical signals

Plant Signaling and Response

Hormones Review • chemical signals that coordinate parts of an organism • produced in one part and transported to another • often work together to induce a change • minute amounts can induce substantial change

Signal Transduction

Signal Transduction 1. Reception: signals are detected by receptor proteins 2. Transduction: second messenger chemicals transfer and amplify the signal from the receptor to proteins that cuase the specific response. 3. Response: regulation of cellular activities by proteins

Plant Hormone Carousel

Tropisms • Any growth response that results in curvatures of whole plant organs toward or away from a stimuli

Phototropism • Phototropism: growth of shoot toward light. • Auxin plays a major role in this response. • Darwin, Boysen-Jensen, and Went experiments with phototropism led to the discovery of plant hormones.

Phototropism Experiments

Gravitropism • Gravitropism: a plant’s response to gravity. • Roots display positive gravitropism. / Shoots display negative gravitropism. • Auxin plays a major role in this response. • Plants may be able to tell up from down by the settling of statoliths.

Thigmotropism • Thigmotropism: directional growth in response to touch. • Thigmomorphogensi s: changes in form that result from mechanical stimuli. • Twining motions of vines video clip (Circumnuation)

Another Touch Response • Thygmonastic Movement ▫ Use action potentials similar to animal nervous-system messages ▫ Change the turgor pressure results in movement • Fly Trap Video Clip

Photoperiodism • Plants use the photoperiod (relative lengths of night and day) to detect the time of year. • Photoperiodism: a physiological response to photoperiod • Plants detect light with photoreceptors such as phytochrome and cryptochrome. • Long day plants are actually short night plants.

Photoperiod and Flowering