How does temperature affect the rate of photosynthesis?

By Luke W, Pat, and Luke T

PredictionsThe room temperature water will have the most photosynthetic

activity over the hot and cold waters because the process of

photosynthesis in spinach leaves have an optimal temperature

where it works best. The optimal temperature for the fastest rate of

photosynthesis will fall between 2°C and 75°C, and more towards

the 24°C water. The difference between the two temperatures will

affect the amount of time it takes for the leaf disks to float.

HypothesisNo leaf disks in the hot and cold water floated throughout the

course of the experiment. The reason for this occurrence was

that the optimal temperature did not include 2℃ and 75℃,

but it was proven that the room temperature fell in the

optimal range at 24℃. If the cold and water contained leaf

disks that floated, a wider optimal range would be discovered.

Experimental Control

The correct way to interpret the data correctly was

by examining which temperatures produce the most

floating leaves.

Materials● Soap (3 drops from pipette total)

● Baking Soda (3 Pinches total)

● 3 Plastic Cups

● 3 Goggles

● Water (6cm/cup)

● Spinach Leaf (36 Disks)

● 3 Syringes

● Hole Puncher

● Lamp

● Timer

● Stirring Rod

● Microwave (Warmed water to 75 Degrees Celsius)

● Ice (Cooled water to 2 Degrees Celsius)

MethodsMade 3 cups of bicarbonate+soap solution. One cup of the bicarbonate soap solution was

placed in a microwave until it reached about 75 degrees celsius. Kept one cup at room

temperature and added ice to the third cup until it was about 2 degrees celsius. The

temperature was recorded initially. Thirty-six spinach leaf disks were hole-punched, placing

12 into each syringe. Each syringe was filled up two thirds to the top with bicarbonate +

soap solution from the cups. The leaves were infiltrated by placing our fingers on the tip

and pulling back on the plunger. Once all the leaves have sunk, each syringe was emptied

into the three cups. Each cup was placed under its own lamp and the timer was started.

Each person watched their own cup and took notes in the data table for how many leaf

disks floated. Once all the leaf disks were floating, the timer was stopped.

Ice Cold Water (2 Degrees Celsius)

No leaf disks

floated during the

25 minutes that

they were

submerged in the

ice cold water.

Room Temp Water (24 Degrees Celsius)

All 12 leaf disks floated

during the 25 minutes that

they were submerged in the

room temperature water.

Hot Water (75 Degrees Celsius)

No leaf disks floated during

the 25 minutes that they

were submerged in the hot

water.

Results and Graphs

The leaf disks in the room temperature water were the only ones to photosynthesize. The other

temperatures were too extreme for any photosynthesis to happen.

Photosynthetic Activity in Different Water Temperatures for Spinach Leaf Disks

-In the cold and hot water, no photosynthetic activity was recorded

-In the room temperature water, the first disk floated after the 7th minute

-All 12 leaves were floating by the 25 minute mark

DiscussionIn the experiment, it was found that 24 degrees celsius is around the optimal temperature

for photosynthesis, which was the room temperature water. There was no photosynthesis

happening with the hot and cold water. These differences in temperature do not affect the

light reactions or the calvin cycle in leaves. The space between these temperatures mostly

affects the enzymes that are catalyzing the chemical reactions. If the temperature is too

cold, the enzymes would move around too slow and won’t meet with the substrates. This

temperature was at 2 degrees celsius in the experiment. At the enzyme's optimal

temperature, they are working very efficiently and bonding to the substrates quickly. This

was our room temperature water at 24 degrees celsius. It can also be too hot for the

enzyme to function, which is anywhere above 40 degrees celsius. Our hot water was at 75

degrees celsius which is well above the optimal temperature. Since all enzymes are

proteins, they will begin to break down when the temperature is too high. The active site

becomes distorted and cannot fit to the substrate. This means the enzyme has been

denatured.

Possible ErrorsThe main error that could have occurred in this experiment was

maintaining the cold and hot temperatures. The hot water could

have lost heat when we took it out of the microwave. This could

have introduced floating leaf disks because the temperature

would near the optimal temperature. Same goes with the cold

water, as taking it out of the ice bath would allow for an increase

in temperature.

ConclusionNo leaf disks in the hot and cold water floated throughout the

course of the experiment. The room temperature water had all

leaves floating by the 25 minute mark. A cause for these results

was an optimal range of temperatures, one that included 24

degrees celsius but excluded 2 degrees celsius and 75 degrees

celsius. At these extremely hot and cold temperatures of water

the enzymes in the chemical reactions were denatured.