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The leaf turns brittle during the testing the leaf for starch because the ethanol extracts the all water content from the leaf.
It can be observed that when testing for starch their must be a olour change of blue black after iodine solution was added.Before the colour change was green that changed to blue black of the whole procedure is been carried out.
so the waxy cuticles can rub off the surface of the leaf. a leaf has a cell wall and if you did not put the leaf in the boiling water it would not break down so therefore you would not be able to do a proper starch test on the leaf so the answer to this question is to break the cell wall down so you can test for starch properly i hope i helped you :) yeap
The presence of starch in plants indicate that photosynthesis has occurred. The process of testing the presence of starch uses iodine solution that turns to blue-black on a positive test.
Most of the starch contained in a leaf is located within chloroplasts.
The leaf turns brittle during the testing the leaf for starch because the ethanol extracts the all water content from the leaf.
to denature the enzymes going to kill the leaf
Use iodine to test a leaf for starch | Plant Physiology | Biology
A hot bath of ethanol decolorizes the leaf by washing out the chlorophyll. If the leaf is not decolorized, you cannot see the blue-black stain that results from the iodine reacting with the starch.
It can be observed that when testing for starch their must be a olour change of blue black after iodine solution was added.Before the colour change was green that changed to blue black of the whole procedure is been carried out.
It is to remove the chloroplast and dissolve in the alcohol and turn it green.
Ethanol dissolves chlorophyll hence further phtosynthetic activity is stopped in the abscence of light and the leaf becomes transparent (colorless). the colorless leaf takes better stain with iodene while testing for the presence of starch.
When the plant is kept in sunlight the starch is formed in leaf.
so the waxy cuticles can rub off the surface of the leaf. a leaf has a cell wall and if you did not put the leaf in the boiling water it would not break down so therefore you would not be able to do a proper starch test on the leaf so the answer to this question is to break the cell wall down so you can test for starch properly i hope i helped you :) yeap
Starch is produced by leaves during Photosynthesis, therefore if the leaf has not been exposed to light then it will not contain starch, and so when tested the Iodine will stay Yellow/Brown. Consequently if the leaf has been left in the light Photosynthesis will have taken place and when tested the Iodine will go Blue/Black showing that Starch is present. Hope this helps :)
Chlorophyll has a function of converting starch into glucose and other simpler plant products.Thats why we have to remove cholorphyll before starting a test for starch.
To determine the location of starch in a leaf, one can examine it under the microscope and apply one small drop of iodine to the leaf. The parts of the leaf that turn purple contain starch.