Adaptations of leave for photosynthesis

Question 1

This leaf has thick external cell walls. Why

Answer 1

The epidermis are thick external walls and with a waxy cuticle on outer surface
- This protects leaf tissue from invasion by fungal parasites and from excessive water loss

Question 2

What is the function of the veins in the leaf

Answer 2

The veins contain small vascular bundles continuous with those of stem and root
- This supports the leaf tissue
Vascular bundle contain xylem and phleom
- The xylem vessels deliver water and dissolved mineral salts to mesophyll cells
- The phleom sieve tubes transport sugars away from the leaf

Question 3

Explain the difference between palisade mesophyll and spongy mesophyll

Answer 3

Palisade mesophyll has elongated cells closely packed together with numerous chloroplasts
- This maximises the light energy absorbed by chlorophyll in the chloroplasts
Spongy mesophyll are mostly spherical cells with some chloroplasts and large interconnecting air spaces (Substomatal air chamber) in between them
- This facilitates gaseous exchange of carbon dioxide and oxygen by diffusion

Question 4

Explain the function of the external shape and structure of the leaf

Answer 4

Most plants have numerous leaves that have a large surface area
- This allows maximum absorption of light energy
Flat lamina
- Facilitates inward diffusion of carbon dioxide into the leaf and oxygen out of the leaf
Petiole holds lamina away from stem
- This holds leaf in position to absorb maximum light energy

Question 5

How does stomata affect photosynthesis

Answer 5

Pores in the leaf epidermis between two guard cells; changes in turgidity of guard cells cause them to open and close
- This allow diffusion of carbon dioxide into the leaf and oxygen out of the leaf (When open in the light)