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प्रश्न
Enumerate the steps involved in testing a green leaf for the presence of starch.
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उत्तर
Test to determine the presence of starch in a leaf:
- Dip a leaf in boiling water for a minute to kill the cells.
- Boil the leaf in methylated spirit in a water bath to remove the chlorophyll, till the leaf turns pale blue and becomes hard and brittle.
- Now place the leaf in hot water to soften it.
- Place the leaf in a Petri dish and pour iodine solution over it.
- The appearance of a blue-black colour on the leaf is indicative of the presence of starch.
- The absence of starch is indicated by a brown colouration.
संबंधित प्रश्न
Expand the abbreviation:
ADP
Describe an experiment to prove that sunlight is necessary for photosynthesis.
A potted destarched plant was taken in order to prove that light is necessary for photosynthesis.
(i) What is meant by 'destarched plant'? How can it be destarched?
(ii) Using the destarched plant describe step by step how you would proceed to prove that in the absence of light the leaf cannot manufacture starch.
Identify the false statements and rewrite them correctly by changing the first or last word only.
Starch produced in a leaf remains stored in it for 2-3 weeks before it is used by other parts of the plant.
A healthy croton plant bearing variegated leaves was kept in a dark cupboard to destarch it after which it was placed in sunlight for a few hours. One of the leaves was then plucked and an outline of the leaf marking the green and the non-green regions was drawn. The leaf was then tested for starch. Using the above information, answer the following questions:
- State the aim of the above experiment.
- Name the chemical used for testing the presence of starch.
- Why is the leaf boiled in water and alcohol before testing for the presence of starch?
- What change is seen on the leaf after the starch test?
- Give the chemical equation to represent the process of starch formation in plants.
A candidate in order to study the importance of certain factors in photosynthesis took a potted plant and kept it in the dark for over 24 hours. Then in the early hours of the morning, she covered one of the leaves with black paper in the center only. She placed the potted plant in the sunlight for a few hours, and then tested the leaf which was covered with black paper for starch.
- What aspect of photosynthesis was being investigated?
- Is there any control in this experiment? If so, state the same.
- Why was the plant kept in the dark before the experiment?
- Describe step by step how the candidate proceeded to test the leaf for the presence of starch.
Name the following:
In-plant cells, carbohydrates are stored in which form.
The reactions of photosynthesis make up a biochemical pathway.
What is the end product of light and dark reactions of photosynthesis?
The reactions of photosynthesis make up a biochemical pathway.
Explain how the biochemical pathway of photosynthesis recycles many of its own reactions and identify the recycled reactants.
Name four essentials for photosynthesis.
