Floating Leaf Disk Assay :- ( LAB REPORT )

Aim: Investigation of Photosynthesis using the Floating Leaf Disk Assay.

Introduction: Leaf disks float, normally.  When the air spaces are infiltrated with solution the overall density of the leaf disk increases and the disk sinks.  The infiltration solution includes a small amount of Sodium bicarbonate.  Bicarbonate ion serves as the carbon source for photosynthesis.  As photosynthesis proceeds oxygen is released into the interior of the leaf which changes the buoyancy--causing the disks to rise.  Since cellular respiration is taking place at the same time, consuming oxygen, the rate that the disks raise is an indirect measurement of the net rate of photosynthesis. The standard procedures such as counting oxygen bubbles generated by an elodea stem. Over the years, these have found the floating leaf disk assay technique to be reliable and understandable.

Requirements: Sodium bicarbonate, Liquid soap hand wash, Plastic syringe, Punching machine, Plastic cup, Leafs, Timer, Light bulb.

Procedure:

1. Obtain enough sodium bicarbonate solution for each trial. You will be using a 0.2% solution, which has a trace amount of liquid soap in it.300 ml of bicarbonate solution for each trial. The bicarbonate serves as an alternate dissolved source of carbon dioxide for photosynthesis. The soap wets the hydrophobic surface of the leaf allowing the solution to be drawn into the leaf.
2. Utilizing a Punching machine cut 10 leaf disks for each trial. Avoid major veins.
3. Infiltrate the leaf disks with sodium bicarbonate solution until only a small volume of air and leaf disk remain in the barrel (< 10%).
4. Pull a small volume (~ 5 mL) of sodium bicarbonate solution into the syringe. Tap the syringe to suspend the leaf disks in the solution. Holding a finger over the syringe opening side, draw back on the plunger (~ 1 mL) to create a vacuum.
5. Hold this vacuum for about 10 seconds. While holding the vacuum, swirl the leaf disks to suspend them in the solution. Let’s off the vacuum. The bicarbonate solution will infiltrate the air spaces in the leaf causing the disks to sink.
6. Pour the disks and solution into a beaker. Add bicarbonate solution to a depth of about 20ml. Use the same depth for each trial. Shallower depths work just as well.
7. This one will be placed under a light source.
8. Place your first sample away for the supplemental light source and your second sample under the light source. Start timing as soon as your sample is set up. At the end of each minute, record the number of floating disks. Then swirl the disks to dislodge any that are stuck against the sides of the cups. Continue until all of the disks are floating.

Observation: noted all the things that were Observed and come to know that the disks come fast up in dark area.

Data table
Minutes	Disks(light)	Disks(Dark)
1	0	2
2	0	4
3	0	4
4	1	6
5	3	5
6	3	6
7	3	6
8	5	8
9	7	9
10	8	10
11	10	-