Photosynthesis & Starch Content

[winefile]

Two healthy and vigorously growing plants are placed in the dark for a day and then placed in air tight bell jars. One bell jar also contains a glass beaker containing Potassium hydroxide and the other was does not. Both are placed in the light and their leaves subsequently tested for their starch content.
What is this experiment designed to determine?

What results would you hypothesise and why?

[mith]

How much KOH are we talking about?

[winefile]

25ml of concentrated solution – absorbs CO2 very effectively

[mith]

there’s your answer isn’t it?

[winefile]

This is what I thought, but comments would be great if in right direction…
Depicts level of starch synthesis after the shut down of photosynthesis from the time in the dark, the absense of CO2 (Pot Hyd) etc. Also perhaps to indicate that plants need CO2 for survival, possibly showing starch consumption during respiration, also determination of oxygen generation during respiration.

Starch is the primary product of photosynthesis. As the bell jar heats up, the tugor pressure will rise in the stomata, releasing water via respiration to cool leaves. The stomata may close after a period (as the plant is vigerous) and realises it cannot keep the plant cool enough. This will stop both photosynthesis and respiration. The plant without Pot Hyd. will use more starch as it will be going through photosynthesis and respiration where as the plant with will only be respiring.
Starch levels will able to be measured with the plant with Pot Hyd being greater than that without, as the plant without will have continued to photosynthesise and respire for longer, using more nutrients.

What do you think?

[MrMistery]

I think you are overthinking. The plant with potassium hidroxide will carry out less photosynthesis, because of the smaller availability of CO2. Therefore, it will use more starch.

[secret]

What’s a bell jar? -curious…

[MrMistery]

a jar shaped like a bell

[asquiths]

Mr mistery

What exactly is the bell jar and where is it located?

thank you

[MrMistery]

a bell jar is placed on the plant to isolate it’s atmosphere from that of the outside "world". this is done in order to carry out certain experiments, like the one in question.

Oh, and by the way, the plant with KOH in it’s jar(if it is a c3 plant) will carry out more photorespiration because of the scarce CO2

[asquiths]

thank you kind sir

[sachin]

CO2 Experiment.

Studied in 6th grade.

CO2 is essential for photosynthesis.

[Author]

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