16.1 Plant Hormones & Growth In Plants Flashcards
(22 cards)
What’s the the four plant hormones to know
Auxins
Gibberellin
Ethene
ABA
What are roles of auxins
Control cell elongation
Prevent leaf fall
Maintain apical dominance
What are roles of gibberellins
Trigger mobilisation of food stores in seed germination
Cause stem elongation
What are the roles of ethene
Cause fruit ripening
Promote abscission in deciduous trees
What are the roles of ABA
Maintain dormancy of seeds and buds
Stimulate cold protective responses like antifreeze
Stimulate stomatal closing
What must be the first thing to happen for a plant to grow
The seed must germinate
What are the first steps of a seed germinating
The seed absorbs water and this activates the embryo and gibberellins begin to be produced
What happens when gibberelins start to be produced in seed germination
The gibberellins stimulate the production of enzymes that break down food stores in the seed
These food stores are used to produce ATP to build materials to grow
What enzymes do gibberellins switch on the genes for in germination of a seed
Amylase and protease
Digestive enzymes
What are some of the experimental evidence for gibberellins
Mutant varies of seeds that have been bred to not have the gene for gibberellins are seeds that don’t germinate
If you add gibberellins biosynthesis inhibitors to seeds they won’t germinate as gibberellins aren’t made
Where are auxins made
In the tips of roots and shoots
How do auxins stimulate growth of main apical shoots
Auxins bind to specific receptor sites causing a fall in pH to 5
This is the opt pH for enzymes needed to keep walls flexible
As cell matures auxin is destroyed and pH rises again so the enzymes become inactive and the walls become rigid abs fixed in shape
What is apical dominance
The main shoot dominates/ inhibits the outgrowth of other shoots
How do auxins cayse apical dominance in roots
High concentration of auxins in apical shoots suppress teh growth of lateral shoots
What does high concentrations of auxins in roots mean
Inhibit roots growth
Shaded roots contain more auxin and so grow less
What is the evidence for auxins working on stem growth
If the apical shoot is removed then the auxin producing cells are removed and so there is no auxin - the lateral shoots are then freed from dominance and the apical shoot grows faster
What is the eve induce for auxin being produced in root tops and auxin reaching roots in low concentrations from growing shoots
If apical shoots are removed then the amount of auxin getting to roots is reduced and root growth slows
What are internodes
The regions between leaves on a stem
What do gibberellins have to do with seed elongation
They effect the length of the internodes
Without gibberellins the plant stems are much shorter makes them less vulnerable to damage by weather and reduces waste
What is synergism
When different hormones work together and give a greater response than on there own
What is antagonism
When hormones have oppsosite effects to one another
What practical investigation can be used to see the effect of hormones on plant growth
Grow seedlings hydrophonically (in nutrient solution) in serial solutions of different hormones
Apply different concentration of hormones to cut ends of stems and roots
