auxin

plant hormones

coordinate plant responses to environmental stimuli

production site

meristems…root and shoot tips

transportation

move by active transport or by mass flow in the phloem

main functions

growth control by mitosis, cell elongation and cell differentiation

step 1

auxin binds to receptor

step 2

ATPase stimulated to pump protons across the cell surface membrane to lower cell wall pH

step 3

potassium ion channels open and potassium moves into cytoplasm to lower cytoplasm water potential…water moves in by osmosis

step 4

expansins are activated due to low pH…loosen linkages between cellulose microfibrils

step 5

brief disruption causes cell expansion without loss of wall strength