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Question
A potted plant was taken in order to prove a factor necessary for photosynthesis. The potted plant was kept in the dark for 24 hours. One of the leaves was covered with black paper in the centre. The potted plant was then placed in sunlight for a few hours.
During the starch test, why was the leaf
(1) boiled in water
(2) boiled in methylated spirit
Solution
(1) The leaf was boiled in water to destroy enzymes so that further chemical changes do not take place in the leaf.
(2) The leaf was boiled in methylated spirit to dissolve chlorophyll.
RELATED QUESTIONS
The diagram alongside refers to an experiment in which the apparatus was set up with the light source 10 cm away from the plant. After 15 minutes the number of bubbles evolved per minute from the cut stem was recorded. The light source was moved to 20 cm away from the plant, left for 15 minutes and the number of bubbles evolved per minute was again recorded. The experiment was repeated with the light source at distances of 40, 60, 80 and 100 cm away from the plant. Plot a graph for the results obtained and answer the following questions.
(i) From the graph it seems likely that the rate of bubbling per minute at 50 cm would have been
(a) 2.0 (b) 2.5 (c) 3.0 (d) 3.5
(ii) The gas produced by the plant during the experiment was
(a) air (b) oxygen (c) carbon dioxide (d) nitrogen (e) hydrogen
(iii) The gas collected comes due to the breakdown of
(a) glucose (b) starch (c) water (d) air (e) ATP
(iv) If ice cubes were added to the water, the rate of bubble formation would
(a) Stay the same.
(b) Increase because more water is added.
(c) Decrease because the temperature drops.
(d) Decrease because water freezes.
(e) Cannot tell from the information given.
(v) If some sodium bicarbonate is added to the water the rate of bubble formation
(a) Increases because more respiration occurs.
(b) Increases because more photosynthesis occurs.
(c) Increases because the gas becomes less soluble.
(d) Decreases because carbon dioxide acts as a limiting factor.
(e) Decreases because respiration decreases.
The chemical substance used to test the presence of starch in the cell of a leaf is ______.
Given below is a schematic diagram to illustrate some aspects of photosynthesis.
- Fill up the gaps, in blank spaces (1-4), by writing the names of the correct items.
- What phenomenon do the thick arrows A and B indicate?
A potted plant was taken in order to prove a factor necessary for photosynthesis. The potted plant was kept in the dark for 24 hours. One of the leaves was covered with black paper in the centre. The potted plant was then placed in sunlight for a few hours.
Draw a neat diagram of a chloroplast and label its parts.
Where are the chlorophyll pigments present in a cell?
Name the following:
The site of light reaction in the cell of a leaf.
Complete the following sentence with appropriate word:
A light-induced reaction which leads to the splitting of water is _____ of water.
Complete the following sentence with appropriate word:
________molecules of chlorophyll make one quantasome.
Complete the following sentence with appropriate word:
Carbon dioxide enters the leaf through _______.
Give reasons/explain:
During the starch test, the leaf is boiled in water.
