Biology Forum › Botany Discussion › Photosynthesis & Starch Content
July 25, 2006 at 11:47 pm #5321
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?
July 26, 2006 at 12:06 am #52130mithParticipant
How much KOH are we talking about?
July 26, 2006 at 12:07 am #52131
25ml of concentrated solution – absorbs CO2 very effectively
July 26, 2006 at 4:03 am #52135mithParticipant
there’s your answer isn’t it?
July 26, 2006 at 4:50 am #52136
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?
July 26, 2006 at 7:34 pm #52176
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.
July 29, 2006 at 12:50 am #52315secretParticipant
What’s a bell jar? -curious…
July 29, 2006 at 8:05 pm #52367
a jar shaped like a bell
November 19, 2006 at 11:04 am #60595asquithsParticipant
What exactly is the bell jar and where is it located?
November 19, 2006 at 11:53 am #60598
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
November 19, 2006 at 2:34 pm #60604asquithsParticipant
thank you kind sir
November 20, 2006 at 3:37 pm #60685sachinParticipant
Studied in 6th grade.
CO2 is essential for photosynthesis.
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