Plant Homeostasis - Xerophytes (Test Updated)

Question 1

What are xerophytes?

Answer 1

A plant that has adapted to live in arid environments. It has developed specialised features that minimise water loss, while maintain gas exchange.

Question 2

Where is water gained in plants?

Answer 2

Through root hairs.

Question 3

How is water lost in plants?

Answer 3

By the evaporation from surfaces and through transpiration through stomata.

Question 4

Why do plants need water?

Answer 4

Photosynthesis.

Question 5

What is the equation for photosynthesis?

Answer 5

CO2 + H2O > C6H12O6 + O2

Question 6

Define transpiration.

Answer 6

The evaporative loss of water from plants usually through small pores called stomata.

Question 7

Describe the 5 points of why transpiration is important.

Answer 7

1. Transpiration supplies photosynthesis with the water.
2. The evaporation from mesophyll cells in the leaves cools the plants.
3. Transpiration stream is necessary for distributing mineral salts throughout the plant.
4. Dissolving gases for exchange.
5. Gaurd cells control water and gas exchange.

Question 8

Describe gas exchange in guard cells

Answer 8

When turgid thin walls stretch more than thicker ones causing them to open. When they lose water they begin to close up reducing gas exchange. They need to take in carbon dioxide for photosynthesis and need to get rid of oxygen.

Question 9

List 6 factors affecting the rate of transpiration.

Answer 9

1. Temperature.
2. Wind.
3. Humidity.
4. Light.
5. Surface area.
6. Soil water.

Question 10

List 6 structural adaptations of xerophytes.

Answer 10

1. Reduction in leaf surface area.
2. Sunken stomata.
3. Deep roots.
4. Rolled leaves.
5. Thick waxy leaf cuticle.
6. Shallow spreading roots.

Question 11

Describe a reduction in leaf surface area as a structural adaptation.

Answer 11

Leaves may be reduced to spines or be long and narrow reducing the area of transpiration. There may be a reduced number of stomata. Small leaf surface reduces evaporation and water loss.

Question 12

Describe sunken stomata as a structural adaptation.

Answer 12

Prevent water loss by increasing the relative humidity near each stoma. It decreases concentration gradient, evaporation and diffusion. This creates a microclimate.

Question 13

List 2 physiological adaptations of xerophytes.

Answer 13

1. Stomata opening at night.
2. Storage of water in succulent tissues.

Question 14

Describe deep roots as a structural adaptation.

Answer 14

Reach water resources underground such as a water table. This increases water uptake preventing dehydration.

Question 15

Describe rolled leaves as a structural adaptation.

Answer 15

Rolled leaves and hair both serve to trap moist air. This reduces the concentration gradient and diffusion rate of water vapour and the evaporation and transpiration rate.

Question 16

Describe a thick waxy leaf cuticle as a structural adaptation.

Answer 16

Is impermeable to water, preventing evaporation and water loss. The cuticle can reflect light, reducing the amount of light absorbed and preventing an increase in the transpiration rate.

Question 17

Describe shallow spreading roots as a structural adaptation.

Answer 17

Collect occasional rainfall and increase water uptake. Reduce the risk of dehydration of the plant.

Question 18

Describe stomata opening at night as a physiological adaptation.

Answer 18

Stomata are closed during the hottest part of the day reducing transpiration and evaporation.

Question 19

Describe the storage of water in succulent tissues as a physiological adaptation.

Answer 19

Plants store water in fleshy stems or leaves for use during dry periods. This reduces water loss during hot dry periods.