A variegated leaf is put in between two pieces of cork inserted in the mouth of a bottle containing a small amount of KOH .The leaf is fixed in such a way that some part of it is inside the bottle; some in between the piece of cork & rest outside. The petiole of a leaf is dipped in water. The whole examination is under proper temperature & light.
Why does photosynthesis takes place in the green parts of leaf situated outside the bottle?

Food is not formed in that portion which is inside the bottle because KOH absorbs CO₂

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Food is not formed in that portion which is in between the bottle because it doesn't get light

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Only the green part of leaf outside bottle gives starch test. The white spots contain no chlorophyll and therefore there is no photosynthesis

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The CO₂ is available for photosynthesis

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Solution

The correct option is C
Only the green part of leaf outside bottle gives starch test. The white spots contain no chlorophyll and therefore there is no photosynthesis

The correct option is C.
Explanation of the correct option:
Variegated leaves are multicoloured leaves.
Mostly in a variegated leaf, the white colour will surround the green colour.
It is because of the absence of chlorophyll in the margin of the leaf.
Chlorophyll is necessary for photosynthesis(the process through preparation of food is done with the help of sunlight, water and carbon dioxide).
Hence the starch test is given only by the green portion of the leaf which is outside the bottle.
Final answer: Photosynthesis takes place only in the green-coloured portion of the variegated leaf due to the presence of chlorophyll.

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A variegated leaf is put in between two pieces of cork inserted in the mouth of a bottle containing small amount of KOH .The leaf is fixed in such a way that some part of it is inside the bottle; some in between the piece of cork & rest outside. The petiole of leaf is dipped in water. The whole examination is under proper temperature & light.

What is the name and purpose of this experiment?

Q. In an experiment, a destarched, long and narrow green leaf (still attached to a potted plant) is introduced into a wide-mouthed glass bottle through an airtight cork. The glass bottle contains some potassium hydroxide solution in its lower part (but the leaf remains above this solution). The whole set-up is placed in sunlight for 2-3 days. The leaf is then taken out. After removing chlorophyll, the leaf is treated with iodine solution. No blue-black colour is produced in the leaf.
(a) Which substance could not be synthesised in the green leaf?
(b) What is the function of potassium hydroxide solution inside the glass bottle?
(c) Which condition necessary for photosynthesis is not fulfilled in this experiment?

Q. Given below is a sketch of a leaf partially covered with black paper and which is to be used in the experiment to show that light is compulsory for the process of photosynthesis:

(a) At the end of the experiment, which of the leaf part/leaf parts labelled I, II and III will become blue-black when dipped in iodine solution?
(b) Which substance will be missing in the leaf part/leaf parts which will not become blue-black when dipped in iodine solution?

Q. In the experiment to show that sunlight is necessary for photosynthesis:
(a) What is done to destarch the green leaves of the potted plant initially?
(b) What is done to a part of destarched leaf so that photosynthesis may not take place in that part of the leaf (before keeping the potted plant in sunlight)?
(c) How is chlorophyll removed from the green leaf before further testing?
(d) Which reagent is used to test the presence/absence of starch in the parts of experimental leaf?

Q. Both the plants 'A' and 'B' were kept in sunlight after watering. The part of the leaf of plant 'B' which was inserted in the glass bottle containing KOH(Potassium hydroxide) did not turn blue in the iodine test/ starch test, indicating the absence of starch. The part of the leaf outside the bottle turns blue in the said test. Photosynthesis didn't occur in that part of the leaf due to the non-availability of _________.

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