16 - plant responses

Question 1

what are the types of plant response

Answer 1

• nastic - non directional response (to environmental stimuli)
• tropism - directional response (to environmental stimuli)

Question 2

what are types of nastic response

Answer 2

• photonasty - flowers or leaves opening due to bright light
• hydronasty - folding of leaves in response to drought
• thigmonasty - response to touch or vibration

Question 3

what are types of tropism response

Answer 3

• phototropism - growth towards/away from light
• chemotropism - growth towards/away from certain chemicals
• geotropism - growth towards/away from gravity
• thigmotropism - growth towards/away from a contact stimulus

Question 4

what is positive tropism

Answer 4

plant grows towards stimulus

Question 5

what is negative tropism

Answer 5

plant grows away from stimulus

Question 6

what controls the growth responses

Answer 6

hormones

Question 7

hormones

Answer 7

• chemicals manufactured in a variety of plant tissues and transported to target cells + tissues
• these hormones bind to specific receptors on the plasma membrane with complementary shapes to enable specificity
• movement occurs by active transport, diffusion and mass flow
• the same hormone might have different effects on different tissues (with complementary receptors)
• some hormones can amplify each other’s effect/work together - synergy
• some hormones can cancel out each other’s effects/have opposite effects - antagonism
• plant hormones are found at low conc - so hard to isolate
• there are multiple interactions between the different chemicals and so it is hard to investigate cause and effect