Unit 4 Exam Flashcards
(40 cards)
On the following sketches, label the guard cell,
stomata, K+ , and H2O. Explain why the stoma
opens when K + accumulates in the guard cells
and closes when the guard cells lose K+ .
water follows k+. If they enter, the cell is turgid and full of water, and stomata open. Stomata close when cells lose
K+ and water.
What plant hormone is produced in response to
water deficiency?
Abscisic acid (ABA)
How does ABA help deal w drought
It travels from roots to rest of plants. It produces NO to tell the guard cells to close the stoma to conserve water.
What does NO do?
It closes stoma to conserve water. It maintains seed dormancy.
What plant hormone is responsible for ripening
of fruit?
ethylene
What environmental conditions would we expect
stomata to be open? Closed?
Why do plants close their stomata when CO2
levels are high inside the leaf?
Why do plants open their stomata when exposed
to light?
Open: In the daytime (light), high humidity, low CO2
Closed: nighttime, drought, low humidity, windy, high CO2, ABA.
high CO2 concentration tells the plant that they have sufficient supply for photosynthesis. They don’t need more CO2.
In the light, plants are undergoing photosynthesis, thye need CO2.
Are the number of genes that turn on/off the
same in roots and leaves for the different
stresses?
plant tissues respond differently to each stress and the length of time they experience the stressful environment.
Which stress generally resulted in the greatest
number of genes that were turned on/off?
Cold stress resulted in more genes changing their expression.
Which two stresses generally resulted in
dissimilar number of genes that were turned
on/off in leaves and roots?
3 and 27 hours of Salt and osmotic stress exposure led to very dissimilar gene expression in roots and leaves makes sense because they experience stresses very differently.
How do plants respond to environmental stress?
plants change their gene expression to respond to environmentaln sicne they cant move. They have more genes for more genetic plasticity.
How does this figure highlight that response?
It shows that plants can either increase or decrease expression of gene is response to differfent stresses. they cAN also change over time.
What is the main conclusion that you can draw
from this results figure with environmental stressors
different genes respond differently to same environmental stressor. same gene does not resond to different stressors the same.
What does this figure suggest about guard cells
and light?
guard cells respond to light via changes in membrane potential. stomata open in response to lgiht,
guard cell resting membrane potential
-50mV
Can guard cells change the
membrane potential when exposed to light? What happens to membrane potential when light
hits guard cells?
Their membrane potential becomes more negative (hyperpolarizes). Positively charged ions (H+) move out of guard cell. K+ moves in and replaces lost H+ and water follows K+ causing guard cells to swell and open stomata.
What hormone do plants release when water
stressed?
ABA
What part of the plant releases ABA? Does ABA cause guard cells to close?
roots release when plant is water stressed. it travels to guard cells to signal them to close. ABA does not cause guard cells to close. It is NO. ABA stimulates production of NO which causes the guard cells to close the stomata.
Based on this figure how does a plant respond to
high levels of CO2?
Plants close stomata in High CO2. High CO2 conc tells plant that they have enough CO2 for photosynthesis. They don’t need more CO2, so they close stomata and conserve water.`
Which direction are
potassium ions and sucrose moving in the guard
cells when exposed to high CO2?
K+ and sucrose move out of cells in high CO2. They will move back in once CO2 returns to normal.
Do more genes tend to increase or decrease
transcription in response to stress?
mroe decrease transcription.
Do more genes tend to change transcription
levels when stressed for short periods of time or
long periods of time?
The longer a plant is stressed, the more genes that start to chnage transcription levels.
Do plants generally have smaller or larger
genomes and number of genes compared to
animals? Explain the difference
plants hace more genes and larger genomes than animals because they can’t move and need to be more genetically plastic to respond to enviornmental changes.
What is the important role guard cells play in
plants? How is their role related to
photosynthesis, water transport, and water
conservation?
Co2 moves into plants at the stomata and O2 leaves via stomata.
Water moves from roots to rest of plant due to transpiration of water at stomata. stomata must be open for water to flow.
If the plant is water stressed, stomata will close to conserve water.
No photosynthesis and no water transport thruout plant.
guard cells help balance photosynthesis and water transpirtation trade-offs.
What causes water to move from the roots to
the leaves in a plant?
evaporation (transpiration) of water through stoma results in pulling of water thoruh all the vessles (like a straw)
