Transport in Plants - Xylem

Question 1

What does xylem tissue do?

Answer 1

Xylem tissue transports water and mineral ions in solution. These substances move up the plants from the roots to the leaves

Question 2

What does phloem tissue do?

Answer 2

Phloem tissue transports organic substances like sugars (in solution) both up and down the plant

Question 3

What are xylem vessels?

Answer 3

Xylem vessels are the part of the xylem tissue that transport the water and ions

Question 4

What is the structure of the xylem vessels?

Answer 4

Xylem vessels are very long, tube-like structured formed from dead cells (vessel elements) joined end to end. There are no end walls on these cells, making an uninterrupted tube that allows water to pass up through the middle easily

Question 5

What two factors help water move up the plants, from the roots to leaves, against the force of gravity

Answer 5

Cohesion and tension

Question 6

How do cohesion and tension help water move up the plant, against the force of gravity?

Answer 6

Water evaporates from the leaves at the top of the xylem - this is transpiration. This creates tension, which pulls more water into the leaf. Water molecules are cohesive so when some are pulled into the leaf other follow. This means the whole column of water in the xylem, from the leaves down to the roots, move upwards. Water enters the stem through the roots

Question 7

What is transpiration?

Answer 7

Transpiration is the evaporation of water from a plants surface, especially the leaves

Question 8

What happens during transpiration?

Answer 8

Water evaporates from the moist cell walls and accumulates in the spaces between cells in the leaf. When the stomas open, it moves out the leaf down the concentration gradient because there is more water inside the leaf than in the air

Question 9

What are the four main factors which affect the rate of transpiration?

Answer 9

1. Light
2. Temperature
3. Humidity
4. Wind

Question 10

Explain how light affects the rate of transpiration

Answer 10

The lighter it is the faster the transpiration rate - there is a positive correlation between light intensity and transpiration rate. This is because the stoma open when it gets light to let in CO2 for photosynthesis. When it is dark the stoma are usually closed, so there’s little transpiration

Question 11

Explain how temperature affects the rate of transpiration

Answer 11

The higher the temperature the faster the transpiration rate. Warmer water molecules have more energy so they evaporate from the cells inside the leaf faster. This increases the concentration gradient between the inside and outside of the leaf, making water diffuse out of the leaf faster

Question 12

Explain how humidity affects the rate of transpiration

Answer 12

The lower the humidity, the faster the transpiration rate - there’s a negative correlation between humidity and transpiration rate. If the air around the plant is dry, the concentration gradient between the leaf and the air is increased, which increases transpiration

Question 13

Explain how wind affects the rate of transpiration

Answer 13

The windier it is the faster the rate of transpiration. Lots of air movement blows away water molecules from around the stomata. This increases the concentration gradient, which increases the rate of transpiration