Plant Transport

Question 1

Why are transport systems needed in multicellular organisms?

Answer 1

In unicellular organisms substances can diffuse directly into and out of cells quickly because there is only a short distance to travel. In multicellular organisms this would be too slow, so a transport system is needed

Question 2

What is the role of the xylem?

Answer 2

The xylem carries water and mineral ions from roots to other parts of the plant

Question 3

What is the role of the phloem?

Answer 3

The phloem transports sugars, like sucrose and animo acids from where they are made in leaves to other parts of the plant.

Question 4

How is water absorbed by root hair cells?

Answer 4

Each branch of a root is covered in microscopic root hair cells, giving the roots a large surface area for absorbing water from the soil. Water is absorbed by osmosis and there is a higher conc of water in soil than ther eis in the plant so water is drawn into the root hair cell

Question 5

What is transpiration?

Answer 5

1. It is caused by evaporation and diffusion of water from a plant’s surface
2. Most transpiration happens at the leaves
3. This causes a slight shortage of a water in the leaf so more water is drawn up through the xylem vessels to replace this, so there is a constant transpiration stream through the plant.

Question 6

How does light intensity affect the rate of transpiration?

Answer 6

• light intensity, the brighter the light the faster the transpiration rate. This is because stomata close as it gets darker, photosynthesis can’t happen in the dark so they don’t need to be open to let CO2 in, when the stomata are closed, little water can escape

Question 7

How does temperature affect the rate of transpiration?

Answer 7

The warmer it is the faster transpiration happens, because the water particles have more energy to evaporate and diffuse out of the stomata.

Question 8

How does wind speed effect the rate of transpiration?

Answer 8

The higher the wind speed, the greater the transpiration rate. If it’s windy the water vapour is swept away from the outside of the leaf maintaining a low conc of water in the air outside the leaf, diffusion then happens quickly.

Question 9

How does humidity effect transpiration rate?

Answer 9

The lower the humidity, the faster transpiration happens. If the air is humid, then there is not a high concentration gradient from the inside to the outside of the leaf.

Question 10

How is a photometer used to estimate transpiration rate?

Answer 10

1. Cut a shoot underwater to prevent air from entering the xylem. Cut at a slant to increase surface area
2. Insert the shoot into the potometer under water, so no air enters
3. Remove apparatus from water, but keep the end of the capillary tube submerged in water.
4. Dry the leaves and then shut off the tap
5. Remove capillary tube from water, allow one air bubble to form and put it back in
6. Record the starting position
7. Time and record the distance the bubble move in 30 mins

Question 11

How do you change factors in this experiment?

Answer 11

Light - use a lamp or put in a cupboard
Temperature- take to a different temp room than control
Humidity - spray water in a clear plastic bag and seal it round the plant (increase humidity)
Wind - use a fan