Unit 6 - Processes in Plants

Question 1

What is the Symplastic route of water through plant roots?

Answer 1

When water moves through the cytoplasm of root cells

Question 2

Define the Aeroplastic route of water through plant roots.

Answer 2

When water moves along the walls of root cells

Question 3

How does the endodermis control water movement in the roots?

Answer 3

The endodermis is water impermeable and thus forces water to gather at specific gaps in this layer

Question 4

What is the function of the Casperian Strip in the absorption of water?

Answer 4

The Casperian Strip is selectively permeable and thus will only allow a certain amount of water to enter the xylem.

Question 5

What are the 3 forces that cause water movement in plants?

Answer 5

• Capillarity
• Root Pressure
• Transpiration Pull

Question 6

Define Capilarity.

Answer 6

The spontaneous movement of water up thin tubes via adhesion and cohesion forces

Question 7

What is Root Pressure?

Answer 7

The difference in pressure in the soil and in the root will cause water to move in between them

Question 8

How does Root Pressure affect water movement in plants?

Answer 8

Water pressure is higher in the soil than in the root which causes water to move from the soil into the root via Osmosis

Question 9

Define Transpiration.

Answer 9

The loss of water as vapour from aerial parts of the plant

Question 10

Name and define the 2 types of transpiration.

Answer 10

• Stomatal Transpiration - loss of water via the stomata

* Cuticular Transpiration - loss of water via the cuticles

Question 11

What is Transpiration Pull?

Answer 11

The ‘sucking’ force caused by transpiration that causes water to be pulled up the xylem, to the leaves.

Question 12

Explain what happens when water is lost via transpiration.

Answer 12

When water is lost via transpiration, aerial parts of the plant, such as the leaves, lose water, and thus decrease in water pressure and potential. By nature, water will move down a pressure and potential gradient. Since the xylem now has higher pressure and potential than the leaves, water will move from the xylem to the leaves.

Question 13

Explain the process of water moving from the xylem to the leaves.

Answer 13

Due to potential difference across the xylem and leaves, water will move from the xylem to the leaves. Transpiration pull will cause most of the movement, while adhesion and cohesion forces will ensure that the water column is unbroken.

Question 14

To complete the water potential and pressure equilibrium, what must occur as the final step?

Answer 14

Water must be absorbed into the roots

Question 15

Name 4 factors that influence transpiration rate and how.

Answer 15

• Temperature - increases
• Light Intensity - increases
• Wind - increases
• Humidity - decreases

Question 16

Define Guttation.

Answer 16

Loss of water through large holes on the leaf called hydrathodes, due to high humidity

Question 17

How and why does wilting occur?

Answer 17

When plants don’t have a supply of water to their roots, they use up the water in their vacuoles instead. This will reduce the size of the vacuoles, reducing turgor pressure in the plant and effectively causing the plant to take on a droopy shape.

Question 18

In what form is food transported in the plant?

Answer 18

Glucose from photosynthesis is converted to sucrose before being transported.