Photosynthesis

Leaf Structure.
-Cuticle
-Upper epidermis
-Palisade mesophyll cell
-Bundle sheath cell
-Xylem
-Phloem
-Lower epidermis
Spongy mesophyll cells
-Guard cell
-Stoma
-Cuticle
-Vein

1. Keep leaf in dark cupboard (48hrs) Then place in light for 24 hrs. This will prove that any starch formed was formed during the experiment.

2.Boil the leaf in water

3.Place in boiling hot ethanol (to remove the chlorophyll)

4.Dip the leaf back in water to soften it

5.Spread across a white tile and add iodine

Showing Chlorophyll is needed for photosynthesis

A plant with variegated leaves is de-starched and then allowed to photosynthesise (light,carbon dioxide and water all present). Iodine is added, if chlorophyll is present, the iodine will turn blue/black, if not it will remain brown

Showing Carbon Dioxide is needed for Photosynthesis

You can remove carbon dioxide from the atmosphere by adding KOH (potassium hydroxide) or soda lime (sodium and calcium hydroxide). So to test, pace aplant in a glass jar with KOH and one without any extra substances. If it has worked correctly, the glass jar with KOH should have nostarch present and the other one should have starch present.

How to measure the rate of Photosynthesis.

1. Collect the volume of Oxygen produced over a period of time.

2.Collect the glucose produced over a period of time

3.Measure the volume of Carbon Dioxide taken into the plant over a period of time

Carbon Dioxide concentration- also has an effect on the rate of photosynthesis.
If you increase the Carbon Dioxide concentration you increase the rate of photosynthesis- up until a certain point and then some other factor limits the reaction rate. The concentration of carbon dioxide can be changed using different concentrations of sodium hydrogencarbonate solution.

Oxygen- used by the plant in respiration- any excess is removed from the leaf by diffusion through the stomata

Glucose- very quickly converted into starch. This starch can then be stored. The starch can be quickly broken back into glucose when necessary to be used in respiration or converted into other essential plant products -

Colour of Hydrogen Carbonate Indicator

High Carbon Dioxide levels-YELLOW

Normal Carbon Dioxide Levels-RED

Low Carbon Dioxide Levels-PURPLE

Economic implications in crop production-

Farmers and crop growers want to make sure that they get the maximum rate of photosynthesis in plants that they are growing because this will give bigger plants with lots of stored starch. They do this by making sure they have all the raw materials needed for photosynthesis (co2, water, heat + light) It is easier to control the factors affecting photosynthesis in a greenhouse than open air.

Paraffin heaters- are often used to increase both temperature and carbon dioxide levels. Water sprinklers and artificial lighting are also frequently used. All of these things cost money but hopefully will ensure a bigger profit as the productivity of the plant is increased