auxins

Question 1

what are plant growth substances?

Answer 1

chemicals produced in the plant t in v low concentrations & transported to where they cause a response

Question 2

what is phototropism

Answer 2

bending of a plant towards a light source

Question 3

IAA

Answer 3

indoleacetic acid = stimulates growth

light inhibits IAA
-> elongates in the shaded side, grows towards the illuminated side

Question 4

what is the choldny went model?

Answer 4

explaining growth curvature as resulting from the unequal distribution of auxin due to lateral transport of auxin

Question 5

where are auxins synthesised?

Answer 5

meristems

-> transported long distances in tbe phloem / short distances in carrier proteins

Question 6

what do auxins do?

Answer 6

bind to protein receptors in the target cell, activates intracellular second messenger signal molecules, activate transcription factors, control tbe transcription of auxin regulated genes

Question 7

how do cells expand

Answer 7

acidification by stimulating proton pumps that move H+ out of the cell.

• > low pH activates expansins, disrupt bonds between hemicelluloses and pectins
• > slippage of polysaccharides
• > bonds reform in new locations

Question 8

what else does acidification do?

Answer 8

increases PD across the membrane, enhances ion uptake into the cell.
-> causes water uptake via osmosis
=> swelling = elongation

Question 9

what’s happening in the meristem?

Answer 9

cells actively divide, and then enlarge, forming a region of elongation adjacent to the meristem