Plant responses to signals

Phototropism

growth response of a plant toward or away from light

Toward light= Positive

away from light= negative

Auxin

Promote elongation in shoot through:

1.) Proton pumps stimulated

2.) H+ causes cell wall loosening

3.) Extra elongation (turgor pressure)

Photomorphogenesis

Change in a plant’s morphology due to exposure to light

Detection

Response due to a photoreceptor

Blue-light photoreceptors

• phototropism

• stomatal opening

• slowing of hypocotyl growth

• chloroplast movement

Red light receptors- Phytochromes

Alternate between two forms

detect light between 630-730 nm

Phytochromes 

Pr-inhibits germination

Pfr- Triggers germination 

seeds initially have the Pr form