Chapter 11 (Transport in Plant) Flashcards
What is osmosis?
Movement of water from high water potential to low water potential across partially permeable membrane.
When does osmosis happen?
Osmosis happens when partially permeable membrane separates two solutions.
What is the name of an artificial partially permeable membrane?
Visking Tubing which has microscopic holes
Where is the visking tubing used?
In kidney dialysis machines
What is the relation between water concentration and water potential?
Directly proportional
Why water potential is low in sucrose solution?
Because water molecules are attracted to the sugar molecules.
What is water potential?
How free the water molecules are able to move.
Water in —– can move freely.
Pure water
The more concentrated solution, ——- the water potential.
Lower
Which keeps the shape of the cell?
Cell wall
What happens when cell absorb water?
The cell swells up, and becomes turgid.
What happens when the cell lost water?
The cell loosens up, and becomes flaccid.
What happens when a cell lost excessive water?
The membrane and cytoplasm split away from the cell wall, and become plasmolyzed.
What does the pressure inside the cell provide?
It supports the non-woody parts of a plant, such as leaves, and hold stems upright. so leaves can carry out photosynthesis properly.
Why is wilting protective action?
It cuts down water loss by reducing the exposed surface area of the leaves and closing the stoma.
Which increases the SA for root?
Root hairs
How does most water pass out of the leaves?
As water vapors
What is transpiration?
Loss of water vapor from the leaves.
What is the transpiration stream?
The flow of water from roots to leaves through xylem vessels in the plant.
What are the functions of the transpiration stream?
- Supplies water to the leaves cell for photosynthesis
- Carries mineral ions dissolved in the water
- Provide water to keep the plant cells turgid
- Allows evaporation from the leaf surface, which cools the leaf
Why do animal cells have low water potential?
Animals’ cells do not have strong walls to resist the changes in internal pressure caused by large movements of water.
What does xylem transport?
Water and mineral ions
What does xylem contain?
Xylem contains dead cells arranged end-to-end, forming a continuous vessels.
What happen to vessels when they become matured?
They contain no cytoplasm, instead they form a lumen which the water passes.
What does xylem contain that prevent the water leakage to sides?
Lignin
What is lignin made by?
Cytoplasm
What does lignification do?
- It make xylem strong enabling them to carry water without collapsing
- It make xylem impermeable to water
What does phloem carry?
Sugar and amino acids
How is end of each phloem formed?
Sieve plate
What does sieve tube transport?
It transport the products of photosynthesis from the leaves to other parts of the plant.
Contents of the phloem can travels up or down the plant.
True
Where is the nucleus that control the phloem sieve tubes?
In the companion cells
Where is xylem and phloem in young stem?
At vascular bundles arranged in a circle around the outer part of the stem.
Where is vascular tissue in root?
In the central core
Why stoma are mainly located in lower leaf surface?
To reduce water loss
- Upper leaf surface is exposed to direct sunlight producing high rate of evaporation
- There is less air movement on the underside of leaves
What happen to stoma in light and dark?
- In the light, water enters the guard cells by osmosis and become turgid, bending outwards and opening up the stoma.
- In the dark, water leaves guard cells and become flaccid closing up the stoma
Why stoma absorb water in the light?
Because guard cells use energy of accumulate solutes in their vacuoles.
What are four main factors that affect the rate of transpiration?
- Light intensity
- Temperature
- Humidity
- Wind speed
Why more light intensity increase the transpiration rate?
Because of the opening of the stomata
Why does more temperature increase the transpiration rate?
Because of the increase rate of evaporation of water
Why less humidity increase the transpiration rate?
Because it reduce the diffusion gradient between the air spaces in the leaf and the external air
Why more wind speed increase the transpiration rate?
Because the moving air removes any water vapor which might remain near the stomata.
What is used to measure the rate of transpiration?
Potometer
What are two types of photometer?
Weight and volume
How does a weight potometer measure the transpiration rate?
It measures the rate of mass loss from a potted plant or leafy shoot, over a period of time.
How does the volume potometer measure the transpiration rate?
It is used to find the transpiration rate by a leafy shoot, by magnifying this uptake in a capillary tube.
Mention the steps to measure the transpiration using simple potometer?
- Cut the plant under water
- Seal it on potometer
- Introduce the bubble in capillary tube
- Measure the distance move by bubble
- Measure the time it take to move using stop watch
- speed = distance / time
- repeat the procedure
