Transpiration Flashcards
What is transpiration stream.
Transpiration is the evaporation of water at the surfaces of the spongy mesosphyll cells in leaves. Loss of WATER VAPOUR mainly from the stomata of the leaves.
What is the guard cells function?
Guard cells: To open and close the stomata, determining how much transpiration occurs.
Guard cells and stomata: to control gas exchange and water loss from the plant.
What is stomata’s function?
Stomata helps to obtain carbon dioxide from the atmosphere, and to remove oxygen produced in photosynthesis.
Helps to reduce water loss
What are cohesive and adhesive forces?
Cohesive- forces between water molecules which hold the water molecules together. Theyre between only water molecules.
Adhesive- helps the water molecules stick to other non water molecules.
What happens if water is scarce?
The plants wilt and possibly die.
Why does water movement in the xylem require cohesion and adhesion?
For the transport of water from the roots to the leaves, since these forces allow water to flow at a good pace, and the forces create a “pull” force, allowing the water molecules to quickly head to the leaves to make up for the water that has been lost due to evaporation.
Little water was lost when the lower surface of the leaves were covered in grease, why?
Lower surface has most of the stomata present, so then the stomata will be covered in grease, so water cannot escape.
How can water move out the stomata?
Water moves from the xylem (from the roots to the leaves) and into the mesophyll cells, and at the surface of the mesophyll cells, the water evaporates and leaves the plant by diffusion through the stomata (since stomata are tiny pores water is able to diffuse)
What happens when less water is available in guard cells?
The guard cells become flaccid (lose, not firm) as a result of osmosis.
less water is enetering so the stomata closes to prevent any more water loss.
What happens when more water is available in guard cells?
The guard cells become turgid (swollen, filled with water) as a result of osmosis.
water enters the guard cells (sometimes in excessive amounts) so the stomata opens, allowing the water to leave.
How can the guard cells determine how much transpiration should occur?
Since the guard cells control whether the stomata opens or closed.
What would happen to the plant if the stomata is closed?
The plant will not be able to exchange gases, like carbon dioxide and oxygen so they will not be able to perform photosynthesis.
Water cannot be lost.
How do we know that the bubble produced in the practical shows a high level of transpiration or low level of transpiration-
The further the bubble travels in the SAME time period, the faster transpiration is occurring.
How does the air bubble get into the capillary tube?
Since we would move the capillary tube from the beaker of water to get a single air bubble to form, then place the tube back into the water
What are the factors affecting/ increasing the rate of transpiration?
Temperature- as temp increases, the rate of evaporation increases ( since the water molecules move faster), SO the rate of diffusion of water from inside the leaf to outside increases, leading to more water vapor loss. The warmer temperatures causes the water molecules to move faster, making it easier to diffuse out the stomata.
Humidity- when humidity decreases, it reduces the concentration of water molecules OUTSIDE/surrounding the leaf. So there will be a steeper concentration gradient (a bigger difference) between the moist air inside the leaf and the dry air surroundings the leaf. Since diffusion occurs from areas of High Conc to low Conc, ( higher water molecules inside the leaf, lower water molecules outside) water vapor diffuses out more quickly, increasing the rate of transpiration. High humidity= slower transpiration, since there will be no concentration gradient. Low humidity= faster transpiration.
Airflow- an increase in air movement results in more water vapor surrounding the leaf to be blown away. So the air surrounding the leaf will be drier. There will be a steeper concentration gradient between the moist/wet air inside the leaf and outside the leaf, so an increase in water vapor being released= more transpiration.
More wind/airflow = faster transpiration
Less wind/still air = slower transpiration
Light intensity- an increase in light intensity causes the stomata (tiny pores) to open wider, since the plants need CO2 for photosynthesis, and an increase in light intensity causes the plant to consume for CO2 for photosynthesis.
When stomata opens wider, more water vapor escaping from the leaf, increasing transpiration.
How can some of the environment factors be investigated during transpiration?
Airflow- set up a fan close by the plant.
Humidity- spray water in a plastic bag then wrap it around the plant.
Light intensity- change the distance of the light source from the plant.
Temperature- increase temperature or decrease temperature of the room
How is the stomata placement related to a reduced level of transpiration?
Stomata is distributed underside of the leaf, where it is cooler and has a lower light intensity since the underside of the leaf is not exposed to much sunlight. Which leads to lower transpiration, leading to less water loss.
What is water vapor? What is humidity?
The gaseous state of water.
An increases concentration of water in the air.
Is there always moist air inside the leaf?why?
Yea, since the water coming from the roots evaporate into the spongy mesophyll cells.
Where does evaporation occur? How?
It occurs in the spongy mesophyll cells.
Water travels from the roots to the leaves via the xylem.
Water moves into the spongy mesophyll cells, in which water evaporates into the air spaces, so the air spaces become saturated (filled) with water vapor, making the air inside the leaf moist. Water+ Air = Moist Air.
Then the stomata diffuses the water vapor.
What can be used to investigate the effect of environmental factors on the rate of transpirations-
Potometer.
What is translocation?
When phloem tissue carries dissolved sugars from the leaves to the rest of the plant.
What is xylems tissues function?
Transports water and mineral ions from the roots to the stem and leaves.
What is transpiration stream?
The movement of water from the roots and through the xylem and out the leaves.
How is xylems structure related to its function?
Xylem has hollow tubes with no end walls: to ensure the CONTINUOUS/ easily flow of water.
Walls are thickened by lignin- to provide structural support and strength of the walls, preventing collapse under water pressure.
Xylem is made up of dead cells- xylem has no organelles (no cytoplasm, nucleus, etc) to provide room for the mineral ions/ water to flow through, so it leaves a hollow lumen (empty space) so there will be less resistance to the flow of water.
How is phloem structure related to its function?
Used to transport sucrose and amino acids in translocation.
Phloem is made up of living cells: sieve tubes contain very few organelles but they’re still made up of living cells, the companion cell provides the sieve tubes with the organelles that are required for necessary functions.
Sieve tubes: very few organelles: to provide room for the sugar molecules to flow through easily, since sieve tubes aid in transporting dissolved sugars from the leaves to the plant. There are end walls (sieve plates) which allows sugars to move across one sieve plate to another.
Companion cell: has all organelles needed to perform specific functions. Mitochondria- releases energy. Nucleus- to control cell activities. Cytoplasm- contains enzymes and proteins needed for the transport of sugars.
Thin cell walls- water molecules can easily flow and enter the phloem through the xylem
