# Experiments to find rate of photosynthesis

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• Created by: Steff06
• Created on: 05-05-16 20:36
How can temperature be measured to see effect on photosynthesis?
Keep all other factors constant. A light intensity used that produces a high rate of photosynthesis. Temperature in water bath altered and vol of gas produced measured at each temp. But warmer water will reduce the solubility of the gas.
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How can carbon dioxide be measured to show its effect on photosynthetic rate?
All other factors kept constant and number of sodium hydrogencarbonate drops varied. Vol of gas produced measured at each carbon dioxide conc.
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How can photosynthetic rate be measured using leaf discs and changing density? Steps 1 +2
1. Use a straw to cut out several leaf discs from cress cotyledons. 2. Place 5/6 leaf discs in a 10cm3 syringe, half-fill syringe with dilute sodium hydrogencarbonate solution.
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What is step 3 for this experiment?
Hold syringe upright and place finger over end. Gently pull on plunger to pull air out of air spaces of spongy mesophyll in leaf discs. Air is replaced by sodium hydrogencarbonate soltuion. As density of discs increases,they sink to bottom of syringe
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Describe the next step of this experiment
Once all discs have sunk, transfer syringe contents to a small beaker. Illuminate from above using bright light and time how long it takes for a leaf disc to float to top. (1/t) is a measure of rate of photosynthesis.
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What are stages 5,6 and 7?
5. Repeat procedure twice more at this light intensity and find mean rate of photosynthesis. 6. Repeat at different light intensities. 7. Put results in table.
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What can be used to measure uptake of CO2?
An indicator solution.
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Why are indicators good for this?
Some indicators are sensitive to small changes in pH.
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Describe the hydrogencarbonate indicator
It is red when neutral, yellow at pH6 and red/purple at pH's slightly above 7.
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## Other cards in this set

### Card 2

#### Front

How can carbon dioxide be measured to show its effect on photosynthetic rate?

#### Back

All other factors kept constant and number of sodium hydrogencarbonate drops varied. Vol of gas produced measured at each carbon dioxide conc.

### Card 3

#### Front

How can photosynthetic rate be measured using leaf discs and changing density? Steps 1 +2

### Card 4

#### Front

What is step 3 for this experiment?

### Card 5

#### Front

Describe the next step of this experiment