Leaf Disc Assay

Question 1

what is photsynthesis?

Answer 1

the process by which plants and other photoautrophs use light energy to synthesize organic compounds from carbon dioxide

6 CO2 + 6 H2O –> C6H12O6 + 6 O2

Question 2

during photosynthesis, CO2 is … to a carbohydrate molecule, while water is …, producing .. as a by product

Answer 2

CO2 is reduced

• water is Oxidized
• producing oxygen

Question 3

what was the purpose of this lab?

Answer 3

to use oxygen production as an assay of photosynthetic rate

Question 4

how was the relative rate of photosynthesis determined?

Answer 4

determined by the time it takes the disks to rise and float –> the greater the rate of photosynthesis the faster the leaf discs will rise to the surface.

Question 5

how are the leaf discs able to float? how did we get the leaf discs to sink?

Answer 5

leaf discs are able to float due to oxygen in the intercellular spaces of the mespohyll tissue in the leafs
-we got lead discs to sink by remove the air from the intercellular spaces using a slight vacuum.

Question 6

how was the concentrations of carbon dioxide in the water increased?

Answer 6

by adding baking soda –> sodium bicarbonate

Question 7

is it possible for leaf disks to float in the control group?

Answer 7

not likely for them to float as they need carbon dioxide as an input in order to produce oxygen as a by product which is responsible for them floating

Question 8

why did leaf discs float at different times?

Answer 8

the leaf discs floated at different times due to the rate which individual leaf discs were photosynthesizing and producing oxygen
-so difference comes from genetic diversity: some leafs disks have more photo-systems and greater amount of space in intercellular spaces, allowing for more oxygen to be able to allow them to float

Question 9

what was the null hypothesis for this report? what was the alternative?

Answer 9

sodium bicarbonate (%) has no effect on the rate of photosynthesis (measured as time in seconds to 50% flotation) of spinach (Spinacia oleracea) leaf discs.
-sodium bicarbonate (%) has an effect on the rate of photosynthesis (measured as time in seconds to 50% flotation) of spinach (Spinacia oleracea) leaf discs.

Question 10

what was the control in this experiment?

Answer 10

distilled water with no added sodium bicarbonate