2.3 Plant Tissues, Organs and Systems

Question 1

How is epidermal tissue adapted for its function? (2)

Answer 1

• Covers the entire plant.
• Has a waxy cuticle which helps reduce water loss from the leaf surface.

Question 2

How is palisade mesophyll tissue adapted for its function? (1)

Answer 2

Contains lots of chloroplasts which allows photosynthesis to progress at a rapid rate.

Question 3

How is spongy mesophyll tissue adapted for its function? (1)

Answer 3

Lots of air spaces allowing gases (including oxygen and carbon dioxide) to diffuse in and out.

Question 4

What are xylem cells?

Answer 4

Dead cells that make up hollow tubes found in the stem, transporting water and dissolved mineral ions in an one-way flow.

Question 5

What are phloem cells?

Answer 5

Elongated living cells in the stem that are made up of vessel cells and companion cells, transporting dissolved sugars and amino acids in a two-way flow.

Question 6

How is the meristem tissue adapted for its function? (1)

Answer 6

Made up of stem cells that can differentiate into many different cell types, allowing the plant to grow.

Question 7

What tissue does the leaf organ contain? (6)

Answer 7

• Epidermis
• Palisade mesophyll
• Spongy mesophyll
• Xylem
• Phloem
• Guard cells

Question 8

What is the function of guard cells?

Answer 8

To control the opening and closing of the stomata, according to the water content of the plant.

Question 9

What is the function of stomata?

Answer 9

To allow the control of gaseous exchange and water loss from the leaf.

Question 10

How are stomata adapted for their function?

Answer 10

• More stomata on the base of the leaf minimising water loss as this side is cooler and shaded.
• Guard cells control their opening and closing.

Question 11

What is the function of root hair cells?

Answer 11

To allow the uptake of water and mineral ions from the soil.

Question 12

What is translocation?

Answer 12

Translocation is the movement of dissolved sugars from the leaves to other parts of the plant.

Question 13

What is transpiration?

Answer 13

Transpiration is the evaporation of water vapour from the surface of a plant.

Question 14

How does transpiration work? (3)

Answer 14

1. Water is absorbed through the roots (from the soil).
2. Water molecules cohere together, pulling up more water in an unbroken column, as they are transported through the xylem.
3. Water evaporates from the leaf surface via the stomata - this evaporation creates a pull that draws more water up the plant, creating a continuous transpiration stream.

Question 15

What are the factors that affect transpiration?

Answer 15

• Temperature - A higher temperature increases the rate of transpiration.
• Humidity - A higher relative humidity decreases in the rate of transpiration.
• Wind speed - An increase in air movement increases the rate of transpiration.
• Light intensity - A greater light intensity increases the rate of transpiration.

Question 16

How does temperature affect the rate of transpiration? (3)

Answer 16

As the temperature increases, the rate of evaporation and diffusion of water increases, which increases the rate of transpiration.

Question 17

How does humidity affect the rate of transpiration? (4)

Answer 17

As the relative humidity increases, the water vapour concentration gradient reduces, decreasing the rate of evaporation, which decreases the rate of transpiration.

Question 18

How does wind speed affect the rate of transpiration? (5)

Answer 18

As air movement increases, the water concentration outside the leaf decreases, increasing the water vapour concentration gradient, which increases the rate of evaporation, and transpiration.

Question 19

How does wind speed affect the rate of transpiration? (5)

Answer 19

As light intensity increases, the rate of photosynthesis increases, allowing more stomata to open, allowing the rate of evaporation to increase, which increases the rate of transpiration.