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| Transpiration |
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| Transpiration is the loss of water in the form of water vapour from the aerial parts of the plant. |
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| Absorption of water |
| Transpiration influences the rate of absorption of water from the soil. |
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| Water movement |
| By transpiration, water moves upwards and as it passes into the cell vacuoles, it makes the cells turgid. This gives form and shape to cells and plant as a whole. |
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| Mineral salt transport |
| The water stream moving upwards carries dissolved minerals with it. Transpiration also helps in distributing these minerals throughout the plant. |
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| Cooling |
| The evaporation of water during transpiration cools the leaves. |
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| Protection from heat injury |
| Some plants like cacti, retain water by reducing transpiration. This saves the plants from high temperatures and strong sunlight. |
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| Temperature |
| Higher the temperature more is the transpiration. |
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| Light |
| Light causes stomata to open and hence increase the water loss from plant. |
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| Diagram Showing Normal Responses of Stomata to Light, CO2,
pH, K+ ion and Water Deficiency |
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| Availability of soil water |
| When the soil gets dry, soil solution becomes more concentrated and the rate of absorption by cells decreases. This leads to reduction in transpiration and stomata close quickly to keep the water loss to minimum. |
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| Atmospheric humidity |
| High humidity means high water vapour pressure outside and it results in lower rate of transpiration and as the humidity decreases rate of transpiration increases. |
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| Wind |
| The wind removes water vapour and thus increases the rate of transpiration. High winds lead to stomatal closure to stop the rapid water loss and hence bring a drop in rate of transpiration. Moderate winds may also reduce transpiration by lowering the temperature of leaf. |
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| Atmospheric pressure |
| Lower the atmospheric pressure, higher is the rate of transpiration. |
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| Water Movement through the leaf to the atmosphere in the form of vapour |
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