16.2 Plant Responses To Abiotic Stress Flashcards
What are abiotic stresses
Changes in environmental conditions
What abiotic stresses cause leaf loss in deciduous plants
Light and temperature changes during the year as they affect the amount of photosynthesis plants do
What is a lack of light called
Photoperiodism
What abiotic stress causes leaf fall/abcission
Why does this happen
The lengthening of dark periods and light levels falling
This causes a fall in auxins
Leaves respond by producing ethene
What does the production of ethene from falling leaves of auxins due to falling levels of light in the day do in the plant
The abscission zone at the base of the plant is sensitive to ethene as ethene swetiches on genes in the cells of the abscission zone and cause them to produce enzymes which weaken the cell walls in the outer layer of the abscission zone
What happens when ethene causes enzymes to be produced on the outer layers of the abscission zones
Vascular bundles are shut off and a layer of protective scar is deposited on the stem side of the seperation layer
Then further abiotic factors like wind and low temps cause further strain on the leaf until it falls off
What is the role of ABA in Stomota control
ABA controls the opening and closing of stomata
The leaf cells release ABA when under stress and this causes stomata to close
What does ABA do to gaurd cells
Activates changes in ionic concentration of gaurd cells reducing turgor of the cells and causing stomata to close
