Nutrition in Plants

Question 1

Describe cuticle and it’s function:

Answer 1

• Waxy layer reduces water loss through evaporation
• Transparent, allowing sunlight to penetrate mesophyll
• Prevents entry of microorganisms

Question 2

Describe the upper epidermis

Answer 2

• Single layer of closely packed cells
• Epidermal cells do not contain chloroplasts except for guard cells
• Secretes cuticle

Question 3

Describe spongy mesophyll layer

Answer 3

• Irregularly shaped cells that are loosely packed allows for rapid diffusion of gases inside leaf
• Numerous large intercellular airspaces
• Less mitochondria than palisade mesophyll

Question 4

How is lamina adapted for photosynthesis?

Answer 4

• Thin allowing sunlight to reach mesophyll cells
• Thin allowing rapid diffusion of CO2 into inner mesophyll cells
• Large surface area to capture maximum sunlight

Question 5

Describe how stomata regulate gaseous exchange?

Answer 5

During the day:

• Light stimulates stomata to open
• Guard cells photosynthesise and synthesise glucose
• Water potential in guard cells decrease
• Water enters the guard cells via osmosis, cell thus becomes turgid
• Guard cells have a thicker cell wall on the side facing the stomatal pore so the cell bends outwards when turgid

At night:

• Glucose is used up
• Water potential increases, water exits cell via osmosis, cell becomes flaccid