Leaves and Photosynthesis

• What adaptations do leaves have for photosynthesis?

Plant cell

cell wall

cell membrane

cytoplasmnucleus

vacuole

chloroplast

Name the structure…

Function Structure

Controls what goes in and out of the cell.

Contains the genetic material.

Surrounds the cell and gives support.

Contains chlorophyll and absorbs sunlight.

Contains cell sap and gives support.

Where all the chemical reactions happen.

cell membrane

nucleus

cell wall

chloroplasts

vacuole

cytoplasm

Chloroplasts absorb sunlight

External: How leaves are adapted for efficient photosynthesis

Leaf blade (lamina)

Apex

Mid-rib vein

Leaf stalk (petiole)

Side vein

Draw this table in your booksFeature of leaves How it aids photosynthesis

Broad, flat leaves

Stomata

Veins

Chloroplasts

Waxy layer

Thin

How leaves are suited to photosynthesis

• Leaves are broad and flat, giving large surface area to absorb as much light as possible.

They have ‘holes’ in the leaves to allow carbon dioxide in and oxygen out. These

are STOMATA.

Guard cells

Stoma

There are veins in the leaves to transport water and sugar around.

Many of the cells are packed with chloroplasts which contain a light trapping pigment- chlorophyll.

There is a waxy layer on top to stop water being lost from the leaf.

Thin leaves provide a short diffusion distance for carbon dioxide to reach the

palisade and mesophyll cells

HT: How structure of the leaf is adapted for efficient photosynthesis

• Epidermis is transparent;• Palisade layer at the top

containing most of the chloroplasts;

• Air spaces in the spongy mesophyll allow diffusion between stomata and photosynthesising cells;

• Internal surface area / volume ratio very large.

Leaf cross section

• In pairs examine a slide of

FT: Plenary

• Use what you now know about leaves and photosynthesis to design an ‘ideal leaf’ that will maximise photosynthesis

• Draw and label your leaf to explain how it is adapted to be more efficient

(You may want to include the external environment it would be found in e.g. A desert or rainforest)

HT: Plenary Questions• Draw this diagram of a Marram grass leaf.

Marram grass is found on sand dunes.

1) What does the waxy cuticle do?2) How does the position of the stomata help this

plant?3) Why are there no stomata on the outer surface of

the leaf?4) Explain the function of the hairs on the inner

surface of the leaves?5) Explain how having sunken stomata will affect

gaseous exchange in the plant, and why this would be an advantage to the plant.