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The following leaf disk experiment performed:

Twenty 5 mm diameter disks were ‘punched’ out of spinach leaves and placed into a plastic syringe. A small volume of 0.2% sodium bicarbonate solution was drawn into the syringe, and a vacuum was created to saturate the leaf’s air spaces with the solution. After all of the disks had sunk in the syringe, they were transferred into a clear plastic cup filled with bicarbonate solution. They were then placed under a light source, and a timer was started.

At the end of each minute, the number of floating disks were recorded.

Which of the following would be a valid question that can be asked about this experimental protocol?


Are the disks floating due to the release of carbon dioxide bubbles as a result of their metabolic processes?


Are the discs floating due to the release of nitrogen gas as a result of the effects of denitrification?


Are the discs floating due to the intake of carbon dioxide through stomatal openings?


Are the discs floating due to the production of oxygen during photolysis reactions?

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