Tag: the leaf
Questions Related to the leaf
Generally, gravitational water is utilized by the plants.
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True
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False
Which of the following is not a type of potometer ?
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Ganong's
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Darwin's
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Newton's
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None of these
Types of Potometer are:-
- Bubble potometer
- Mass potometer
- Ganong's potometer
- Darwin's potometer
Approx. _______ of the water absorbed by a plant is lost in transpiration.
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20-40%
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98-99%
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1-2%
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6-8%
Approx. 98-99% of the water absorbed by a plant is lost in transpiration. Hardly 0.2% is used in photosynthesis while the remaining is retained in the plant during growth.
Significance of transpiration lies in
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Circulation of water
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Absorption and distribution of water
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Regulating the temperature of the plant body
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All of the above
Transpiration generates tension in plants. This tension is the main pulling force which pulls water to great heights in vascular plants. Thus, transpiration leads to the ascent of sap. Without transpiration water and minerals will not rise from roots to aerial parts of plants and trees. Transpiration also causes surface cooling of leaves and hence regulates the temperature of the plant body. At the same time, it is essentially a wasteful process. As much as 99 percent of water absorbed by a plant goes waste into the atmosphere. Thus, transpiration has been called as a necessary evil.
Exchange of gases occur through
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Stomata
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Lenticels
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Root surface
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All of the above
In plants, gas exchange occurs through small pores in the leaf surface called stomata. Stomata can open to allow the exchange of gasses and close to reduce water loss from the plant. In the covering of the secondary structure of the stem of woody plants gas exchange is made through the lenticels of the periderm (small breaches of the cork). The cork of mature roots is also perforated by non-suberized pores called lenticels. These enable oxygen to reach the intercellular spaces of the interior tissues and carbon dioxide to be released into the atmosphere.
Which of the following processes lower the temperature of leaves cooling effect?
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Respiration
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Photosynthesis
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Transpiration
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Hydrolysis
Transpiration is essentially similar to evaporation of water. It is the loss of water in vapour form through stomata. Water molecules tend to remain in the liquid state rather than moving to vapour state; so during evaporation water molecules absorb a lot of heat energy, this generates a cooling effect.
Plant use _____ % of the absorbed water.
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$1$
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$10$
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$100$
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$5$
The plant uses only $1\%$ of the absorbed water for its own needs the rest of the water is lost in the atmosphere through transpiration.
If transpiration stops than
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Upward movement of water by roots will stop.
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Turgidity of the cells will be not be affected at all.
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All metabolic processes will stop.
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Upward movement of water by roots will continue and all the metabolic processes will occur as usual.
Most acceptable theory for the ascent of sap is the 'Physical force theory', called as 'Cohesion-Tension' or 'Cohesion-Transpiration pull theory'. This theory was put forward by Dixon and Joly. According to this theory ascent of sap in plants is a physical process, the lifting force for which is provided by the pulling force generated by transpiration.
Which of the following can regulate the rate of transpiration?
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Endodermal cells
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Mesothermal cells
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Stomata
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Roots
Stomata can regulate the rate of transpiration by simply controlling how open or closed they are (via the guard cells). Stomata that are open wider will facilitate a greater rate of transpiration, while stomata that are more narrowly opened will reduce the rate of transpiration.
Water is ideal material for disposal of excess solar energy because
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Water is easily available and its specific heat is high
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Water evaporates from leaf surface and its latent heat is high
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Water is general solvent
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Upward movement of water creates a difference in water potential
When plants use solar energy for the synthesis of their food, only a small part of solar energy used, rest of the part of this energy evaporate from the surface of leaves by the process of transpiration and due to its high latent heat. It is the best material for disposing excess solar energy.