Plant hormones Flashcards
What is it called when a plant has directional growth?
tropisms
What does abscisic acid do?
maintains dormancy, stimulates cold protective responses
What does ethene do?
causes fruit ripening, promotes abscission in deciduous trees
What do gibberellins do?
cause stem elongation, trigger the mobilisation of food stores in a seed, stimulate pollen tube growth in fertilisation
What happens at seed germination?
When the seed absorbs water, the embryo is activated and begins producing gibberellins. These stimulate the production of enzymes which break down food stores. These are used to produce ATP so the plant can grow and break out of the seed coat. Evidence suggests gibberellins switch on genes which codes for amylases and proteases.
What is the evidence that suggests gibberellins role in seed germination?
-mutant varieties of seeds have been bred without the gene that enables production of gibberellins, they didn’t germinate
Where is IAA produced?
shoot and root tips and meristems
What is apical dominance?
auxins stimulate growth of the apical shoot and inhibits the growth of the lateral shoots
Why do the lateral shoots at the bottom of the plant grow better than further up?
lower conc of auxin especially as the plant grows taller
What is evidence of apical dominance?
if apical shoot removed then lateral shoots grow faster
or if auxin is applied artificially to the apical shoot apical dominance is reasserted
How are gibberellins involved in stem elongation?
They affect the distance between internodes- the regions on the stem between leaves
Why would farmers want plants with short stems?
reduces waste, makes them less vulnerable to weather and harvesting
What does synergistic mean?
work together
What doe antagonistic mean?
oppose each other
What is called when plants are sensitive to a lack of light in their environment?
photoperiodism
