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प्रश्न
What causes the opening and closing of guard cells of stomata during transpiration?
उत्तर
The tiny pores present on the surfaces of leaves, called stomata, help in the exchange of gases. Each stoma consists of bean-shaped or dumbbell-shaped guard cells. The epidermal cells surrounding the guard cells are modified to form subsidiary cells. The opening and closing of the guard cells is caused by a change in their turgidity. The inner walls of the guard cells are thick and elastic, while the outer walls are thin. The numerous microfibrils present in the guard cells facilitate the opening and closing of the guard cells.
At the time of the opening of the stomata, the turgidity of the guard cells increases. As a result, the outer walls bulge and the inner walls become crescent-shaped. The stomatal opening is facilitated by the radial arrangement of the microfibrils.
At the time of the closing of the stomata, the guard cells lose their turgidity, the outer and inner walls retain their original shapes, and the microfibrils get arranged longitudinally.
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संबंधित प्रश्न
An apparatus, as shown below, was set up to investigate a physiological process in plants. The setup was kept in sunlight for two hours. Droplets of water were then seen inside the bell jar. Answer the questions that follow:
- Name the process being studied.
- Explain the process named above in Q.3(a)(i).
- Why was the pot covered with a plastic sheet?
- Suggest a suitable control for this experiment.
- Mention two ways in which this process is beneficial to plants.
- List three adaptations in plants to reduce the above mentioned process.
The set up shown alongside was kept in sunlight for an hour. It was observed that drops of water appeared on the inside of the polyethylene bag.
- Name the process which is being demonstrated.
- Why was the pot and its soil left uncovered by the polythene bag?
- Why was the pot left in the sunlight?
- Suppose the pot in this experiment was placed inside a dark room instead of placing it in sunlight for some time. What difference will be noticed?
Define the three processes by which plants absorb water and minerals from the soil.
Define the term Transpiration stream
How does transpiration help in the uptake of water from the soil?
(a) State whether the following statement are True or False.
(b) Rewrite the false statement in the correct form by changing either the first or the last word only.
Most transpiration occurs at midnight.
Given below is a diagrammatic sketch (surface view) of a stomatal apparatus from a dicot leaf.
(a) Label the parts numbers 1-3
(b) Is this state, open or closed?
(c) Is this stoma, of a dicot leaf or a monocot leaf?
(d) Redraw a sketch of the stomatal apparatus in the state opposite to the one shown here.
The diagram given alongside is an apparatus used to study a particular phenomenon in plants.
(i) Name the apparatus.
(ii) What is it used for?
(iii) What is the role played by the air bubble in this experiment?
(iv) Of what use is the reservoir?
Give a reason.
What happens to the movement of the air-bubble if the apparatus shown above is kept in front of a fan?
Given alongside is the diagram of an experimental set-up to demonstrate a certain phenomenon in plants.
Would it make a difference if the experimental set-up is kept in bright sunshine?
Define the following Term:
Transpiration
Mention, if the following statement is True or False. If false rewrite the wrong statement in its correct form:
Calcium chloride paper is used to demonstrate transpiration
Plants lose water by the process of transpiration.
What causes the opening and closing of guard cells of stomata during transpiration?
Boojho wanted to test the presence of starch in leaves. He performed the following steps.
- He took a leaf and boiled it in water.
- He placed the leaf in a petri dish and poured some iodine over it.
He did not get the expected result. Which step did he miss? Explain.
Name the structures through which Transpiration occur in a plant.
Define the following term:
Wilting
