Plant Hormones and Responses Flashcards
Why do plants need hormones?
They have no nervous system and they are not mobile but they can still communicate between cells and even between different plants
What effect do auxins have on a plant?
control cell elongation, prevent leaf fall, maintain apical dominance
What is the role of gibberellins within a plant?
cause stem elongation, triggers germination, delays ripening and ageing
What does ethene do?
promotes fruit ripening and dropping
What does ABA do?
maintains dormancy of seeds and buds and helps plants in cold
How do hormones control seed germination?
Seed absorbs water
Embryo is activated and begins to produce gibberellins
Gibberellins break down food stores which creates ATP
This allows it to grow and break out of seed coat
How do leaves fall?
Falling light levels in winter causes auxins concentrations to fall. Low auxin concentrations means leaves produce ethane. Ethene initiates gene switching causing new enzymes to be produced that digest cell walls in separation layer. Others cells in separation layer take up more water putting strain on the weakened cells. Leaf falls off.
How does the plant prepare for leaf fall?
Vascular bundles are cut off. Fat material is deposited stem side of separation layer.
How does auxin cause plant growth?
Auxin binds to receptors in cell membrane. This causes pH to fall to pH 5 which is optimal for certain enzymes which keep walls flexible. As cell matures auxin is destroyed and pH rises so cells become rigid again.
How are the stomata controlled?
ABA. Leaf cells release ABA when plant needs to conserve water. It binds to receptors on cell surface membrane of guard cells. Activates changes in ion concentration in cell, so water potential drops and so does turgor so the stomata close.
