Leaves and Photosynthesis
•What adaptations do leaveshave for photosynthesis?
Plant cell
cell wall
cell membrane
cytoplasm
nucleus
vacuole
chloroplast
Name the structure…
Function
Structure
Controls what goes in and out of thecell.
Contains the genetic material.
Surrounds the cell and gives support.
Contains chlorophyll and absorbssunlight.
Contains cell sap and gives support.
Where all the chemical reactionshappen.
cell membrane
nucleus
cell wall
chloroplasts
vacuole
cytoplasm
Chloroplasts absorb sunlight
External: How leaves are adapted for efficientphotosynthesis
Leaf blade(lamina)
Apex
Mid-rib vein
Leaf stalk(petiole)
Side vein
Draw this table in your books
Feature 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, givinglarge surface area to absorb as muchlight as possible.
They have ‘holes’ in the leaves to allowcarbon dioxide in and oxygen out. Theseare STOMATA.
Guard cells
Stoma
There are veins in the leaves to transportwater and sugar around.
Many of the cells are packed withchloroplasts which contain a light trappingpigment- chlorophyll.
There is a waxy layer on top to stop waterbeing lost from the leaf.
Thin leaves provide a short diffusiondistance for carbon dioxide to reach thepalisade and mesophyll cells
HT: How structure of the leaf is adapted forefficient photosynthesis
• Epidermis is transparent;
• Palisade layer at the topcontaining most of thechloroplasts;
• Air spaces in the spongymesophyll allow diffusionbetween stomata andphotosynthesising cells;
• Internal surface area / volumeratio very large.
Leaf cross section
•In pairs examine a slide of
FT: Plenary
•Use what you now know about leaves andphotosynthesis to design an ‘ideal leaf’ that willmaximise photosynthesis
•Draw and label your leaf to explain how it isadapted to be more efficient
(You may want to include the external environmentit 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 thisplant?
3)Why are there no stomata on the outer surface ofthe leaf?
4)Explain the function of the hairs on the innersurface of the leaves?
5)Explain how having sunken stomata will affectgaseous exchange in the plant, and why this wouldbe an advantage to the plant.