Leaf Structures and their Functions

Question 1

Description of lamina

Answer 1

Flattened area of the leaf

Question 2

Function of lamina

Answer 2

Provides a large surface area for absorption of light and for gaseous exchange

Question 3

Description of mid rib

Answer 3

Large central vein of the leaf

Question 4

Function of midrib / veins

Answer 4

Contains the vascular bundles of the leaf to transport water, mineral salts and manufactured food

Question 5

Description of petiole

Answer 5

Stalk that attaches the lamina to the vein

Question 6

Function of petiole

Answer 6

1. Holds the lamina away from the stem so that the lamina can obtain sunlight and air
2. Allows water and mineral salts to be transported to the leaf and manufactured food away from the leaf

Question 7

Description of cuticle

Answer 7

Thin, waxy and transparent layer on upper and lower epidermis

Question 8

Function of cuticle

Answer 8

1. Reduces water loss due to evaporation
2. Transparent - allows light to pass through and enter the leaf

Question 9

Description of (lower and upper) epidermis

Answer 9

• one-cell thick
• stomata present, more stomata in the lower epidermis than upper epidermis
• cells do not contain chloroplasts

Question 10

Function of (lower and upper epidermis)

Answer 10

1. Protects the leaf
2. Reduces water loss from evaporation
3. Allows carbon dioxide to diffuse in and oxygen to diffuse out of the leaf for photosynthesis

Question 11

Description of palisade mesophyll tissue

Answer 11

• cells are long and cylindrical
• cells are closely packed
• cells contain numerous chloroplasts, more than spongy mesophyll

Question 12

Function of palisade mesophyll tissue

Answer 12

Main site of photosynthesis, due to highest number of chloroplasts per cell
Chloroplasts contain chlorophyll which absorbs light energy to synthesis glucose
More light can be absorbed near the upper leaf surface

Question 13

Description of spongy mesophyll tissue

Answer 13

• cells have irregular shape
• cells are loosely packed
• cells contain few chloroplasts, fewer than palisade mesophyll
• thin film of moisture covers mesophyll cells
• surrounded by large intercellular air spaces

Question 14

Function of spongy mesophyll tissue

Answer 14

Function of thin film of moisture
1. Allows water to exit mesophyll cells
2. Allows oxygen and carbon dioxide to dissolve in the thin film of moisture for the diffusion of gases in and out of the mesophyll cells

Function of intercellular air spaces
1. Allows diffusion of oxygen and carbon dioxide within the leaf
2. Allows diffusion of water vapour within the leaf
3. Allows diffusion of oxygen and carbon dioxide in and out of the mesophyll cells for photosynthesis