What is Leaf Flotation Techinique?

Question

I only know it is a method to measure the rate of photosynthesis and it is more accurate than common method of "measuring the number of bubbles evolved". So can anybody tell me what 'Leaf Flotation Technique' is?

Answer 1

This is a fun, easy, and graphic way to measure photosynthesis.

1. Use a standard paper hole-punch to make about 10 leaf disks or circles from the selected leaf. Try to avoid the larger leaf veins.
2. Put the leaf disks into a syringe partly filled with a solution of water, a small amount of baking soda, and a tiny bit of detergent.
3. Squeeze all of the air out of the syringe. Cover the end (no needle, of course) with a fingertip and pull back on the plunger to generate a vacuum inside the syringe. Hold the vacuum momentarily and then release the plunger to check if the leaf disks have sunk. If they haven't all sunk, repeat the vacuum technique.

Here's what has happened. The detergent breaks the surface tension of the water so the water will enter through the stomata. The vacuum makes the water go in through the stomata and into the spaces within the mesophyll layer of the leaf. When the leaf disk is full of the solution, it sinks.

Now put the disks into your testing situations - different colors of light, different light intensity, different temperatures, different concentrations of baking soda, ...

Record how many leaf disks are floating - one minute intervals should be fine.

The disks float as photosynthesis occurs. The baking soda provides carbon dioxide for photosynthesis. As photosynthesis happens, oxygen is generated in the leaf spaces and the leaf disks float.

Have fun. Makes me want to do this right now!