seeds absorb water, embryo activated and begins to produce gibberellins
stimulate production of enzymes that break down food stores found in seeds - cotyledons in dicot seeds
embryo plant uses stores to produce ATP for building material so can grow and break out seed coat
gibberellins switch on genes that code for amylases and proteases - digestive enzymes for germination
what does other evidence suggest about ABA in germination?
ABA acts as an antagonist to gibberellins (interferes with its action)
it is the relative levels of both hormones which determine when a seed will germinate
what evidence is there to support role of gibberellins in seed germination?
mutant seeds - lack gene that enables gibberellins to be made, seeds don't germinate, if gibberellins applied externally then germinate normally
gibberellin biosynthesis inhibitors - if applied, seeds don't germinate as can't make gibberellins needed for then to breakdormancy, if inhibitor removed, or gibberellins applied, seeds germinate
