Question

a leaf of celeous plant is taken a part of this leaf is non green and the remaining is greeen on doing stach test with iodine solution which part of leaf will turn to blue black and why

Answer 1

ANSWER
The given experiment proves that for photosynthesis, the presence of sunlight is an important factor which is absorbed by the chlorophyll (green pigment) present in the chloroplast.
The leaf from a potted plant which was kept in a dark room for 24 hours when tested for starch will not turn blue-black (starch is tested with iodine which gives a blue-black colour if present).
This happens because when the potted plant was kept in a dark room (destarch), the plant was unable to prepare its food by photosynthesis.
So, the leaf A will give a negative test for starch.
Variegated leaves are those which have one colour on the inner region of the foliage and another colour along the edges or margin of the leaf.
Example of a plant with a variegated leaf is Cornus alba Elegantissima.