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Question
Which of the following components was common to both variegated leaf experiment and Mohl’s half leaf experiment?
Which of the following components was common to both variegated leaf experiment and Mohl’s half leaf experiment?
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Solution
The correct option is B Iodine
Variegated leaf experiment was done to find out the significance of the green parts of the leaves. Iodine test was performed on the green and non-green oarts of a variegated leaf.
A positive result for the iodine test showed a colour change ranging from violet to black which indicated the presence of starch as a result of photosynthesis in green parts. A negative result meant no change in colour of the iodine solution indicating absence of starch and hence absence of photosynthesis in non-green parts.
Therefore it was concluded that chlorophyll responsible for the green colour is also responsible for photosynthesis.
Mohl conducted another experiment. He left a potted plant in a dark room for two to three days so that all the starch reserve in them gets used up. Leaves were collected from this plant at the end of three days.
He performed the experiment by putting a small part of a single leaf through the split cork into the bottle containing KOH. KOH drained off the remaining CO2 from the bottle. This whole setup was exposed to sunlight for 3 or 4 hours. At the end of that period, leaves were collected and starch test was performed on them.
Blue black colour indicating the presence of starch was observed in part of the leaf outside the bottle whereas no colour change was observed in the regions of the leaf inside the bottle.
Since the whole setup had the same amount of exposure to sunlight and since it had access to water and chlorophyll, it was concluded that CO2 was the missing factor that prevented the part of the leaf present inside the bottle from synthesising starch using the process of photosynthesis.
So starch test using iodine was a common factor in both these experiments.
Variegated leaf experiment was done to find out the significance of the green parts of the leaves. Iodine test was performed on the green and non-green oarts of a variegated leaf.
A positive result for the iodine test showed a colour change ranging from violet to black which indicated the presence of starch as a result of photosynthesis in green parts. A negative result meant no change in colour of the iodine solution indicating absence of starch and hence absence of photosynthesis in non-green parts.
Therefore it was concluded that chlorophyll responsible for the green colour is also responsible for photosynthesis.
Mohl conducted another experiment. He left a potted plant in a dark room for two to three days so that all the starch reserve in them gets used up. Leaves were collected from this plant at the end of three days.
He performed the experiment by putting a small part of a single leaf through the split cork into the bottle containing KOH. KOH drained off the remaining CO2 from the bottle. This whole setup was exposed to sunlight for 3 or 4 hours. At the end of that period, leaves were collected and starch test was performed on them.
Blue black colour indicating the presence of starch was observed in part of the leaf outside the bottle whereas no colour change was observed in the regions of the leaf inside the bottle.
Since the whole setup had the same amount of exposure to sunlight and since it had access to water and chlorophyll, it was concluded that CO2 was the missing factor that prevented the part of the leaf present inside the bottle from synthesising starch using the process of photosynthesis.
So starch test using iodine was a common factor in both these experiments.
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