Transport In Plants

Question 1

What is the transpiration rate affected by?

Answer 1

Light intensity
Temperature
Air movement
Humidity

Question 2

What must healthy plants do?

Answer 2

Balance water loss with water uptake

Question 3

What do both xylem and phloem form?

Answer 3

Continuous systems in leaves, stems and roots

Question 4

Relate xylem to its function

Answer 4

Xylem - transpiration - movement of water and minerals from the roots to the shoot and leaves

Question 5

Relate phloem to its function

Answer 5

Phloem - translocation- movement of food substances (sugars) up and down stems to growing and storage tissues

Question 6

Describe the structure of xylem vessels

Answer 6

Thick strengthened cellulose cell wall with a hollow lumen (dead cells)

Question 7

Describe the structure of phloem

Answer 7

Columns of living cells

Question 8

What is transpiration?

Answer 8

The evaporation and diffusion of water from inside leaves

Question 9

Describe how transpiration causes water to be moved up xylem vessels

Answer 9

• water evaporates from the internal leaf cells through the stomata
• water passes by osmosis from the xylem vessels to leaf cells, which pulls the entire thread of water in that vessel upwards by a small amount
• water enters the xylem from root tissue to replace water which has moved upwards
• water enters root hair cells by osmosis to replace water which has entered the xylem

Question 10

Explain how the structure of a leaf is adapted to reduce excessive water loss

Answer 10

• waxy cuticle

- small number of stomata on upper surface

Question 11

What does transpiration provide plants with water for?

Answer 11

Cooling
Photosynthesis
Support
Movement of minerals

Question 12

Explain how the cellular structure of a leaf is adapted to reduce water loss?

Answer 12

• changes in guard cell turgidity

Question 13

Explain why transpiration is increased by:

• increase in light intensity
• increase in temperature
• increase in air movement
• decrease in humidity

Answer 13

• more light increase rate of photosynthesis so increases transpiration
• rate of photosynthesis increase as temperature increases so increases transpiration
• transpiration increase as the movement of air increases
• decreased humidity increases transpiration as there would be less water vapour in the air

Question 14

Describe how water travels through a plant

Answer 14

• absorption from soil through root hairs
• transport through the plant, up the stem to the leaves
• evaporation from the leaves (transpiration)