Photosynthesis & Starch Content

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winefile
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Photosynthesis & Starch Content

Post by winefile » Tue Jul 25, 2006 11:47 pm

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?

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mith
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Post by mith » Wed Jul 26, 2006 12:06 am

How much KOH are we talking about?
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Post by winefile » Wed Jul 26, 2006 12:07 am

25ml of concentrated solution - absorbs CO2 very effectively

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Post by mith » Wed Jul 26, 2006 4:03 am

there's your answer isn't it?
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Post by winefile » Wed Jul 26, 2006 4:50 am

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?

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Post by MrMistery » Wed Jul 26, 2006 7:34 pm

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.
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Post by secret » Sat Jul 29, 2006 12:50 am

What's a bell jar? -curious...
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Post by MrMistery » Sat Jul 29, 2006 8:05 pm

a jar shaped like a bell
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jell bar?

Post by asquiths » Sun Nov 19, 2006 11:04 am

Mr mistery

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

thank you

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Post by MrMistery » Sun Nov 19, 2006 11:53 am

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
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Post by asquiths » Sun Nov 19, 2006 2:34 pm

thank you kind sir

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Post by sachin » Mon Nov 20, 2006 3:37 pm

CO2 Experiment.

Studied in 6th grade.

CO2 is essential for photosynthesis.
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