Practical Testing on Photosynthesis Flashcards
How do you test for starch in a leaf?
You dewax in boiling water for 30 sec on a bunsen burner.
It is turned off when the leaf is placed in a boiling tube with ETHANOL and is placed in the hot water
The ETHANOL will boil in the water until it the water cools down. The longer it is left in the ETHANOL the more chlorophyll gets extracted.
The leaf is then washed in cold water and then placed on a tile and covered with iodine solution.
Any parts that contain starch will turn a DARK BLUE/BLACK
How do you investigate the effect of light on a gas exchange?
10ml of Hydrogen carbonate indicator is placed at the bottom of 4 boiling tubes
You place three large leaves in all three in the boiling tubes and each boiling tube is sealed with a rubber bung.
One is placed in bright light, one in the dark (covered with silver foil), The third is covered with a translucent material. The fourth acts as a controlled experiment with no leaf.
Light= Purple, Dark= Yellow, Dim light= Orange, Control= Orange.
High concentration= yellow, Normal CO2=Orange. Low concentration= purple
How to measure the rate of photosynthesis?
Use a pondweed called Elodea an aquatic plant. Put it in a boiling tube with water and place that boiling tube in a beaker with water and a thermometer. Have a light shine on the plant. Then count the number of bubbles formed per minute.
Have Elodea in a beaker with water with a rubber bung connected to a gas syringe then record the volume.
Use a data probe that is hooked up to the digital instrument like a computer, that records the data.
