role of plant hormones

Leaf loss

AUXIN ETHENE CYTOKININS

• light levels decrease

• less auxin produced

• more ethene produced

• enzymes produced to weaken cell walls

• separation layer formed

stomatal control

• ABSICIC ACID:

• binds to receptors and causes Ca channels to open. (diffuse in)

• K diffuse out and water potential increases.

• H2O moves out and becomes flaccid.

seed germination

• GIBBERELLINS.

• seeds absorb water, embryos activate

• release gibbrellins

• cause amylase production

• amylase breaks down starch into glucose

• glucose used in respiration to release energy used by embryo to grow.

stem/cell elongation

• promotes active transport of H+ by ATPase into cell walls.

• lowers pH = enables optimum conditions for enzymes to break bonds with cellulose.

• disrupts H bonds within cellulose.

• becomes less rigid and expands as it takes in H2O

auxin use

• rooting powders: makes lots of plants from a few cells.

• seedless fruit: easier to eat

• hormonal weed killers

cytokinins use

• prevent ageing of ripened fruit: longer shelf life

gibbellins use

• delay ripening + ageing: allows fruits to be kept for longer

ethene

• ripen fruit + promote plant drop: easier to collect and pick