transpiration
Americannoun
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an action or instance of transpiring.
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Botany. the passage of water through a plant from the roots through the vascular system to the atmosphere.
Closer Look
Plants need much more water than animals do. But why? Plants use water not only to carry nutrients throughout their tissues, but also to exchange gases with the air in the process known as transpiration. Air, which contains the carbon dioxide that plant cells need for photosynthesis, enters the plant mainly through the stomata (tiny holes under its leaves). The air travels through tiny spaces in the leaf tissue to the cells that conduct photosynthesis. These cells are coated with a thin layer of water. The cell walls do not permit gases to pass through them, but the carbon dioxide can move across the cell walls by dissolving in the water on their surface. The cells remove the carbon dioxide from the water and use the same water to carry out oxygen, the main waste product of photosynthesis. All this mixing of water and air in transpiration, though, has one drawback: more than 90 percent of the water that a plant's roots suck up is lost by evaporation through the stomata. This is why a plant always needs water and why plants that live in dry climates, such as cacti, have reduced leaf surfaces from which less water can escape.
Etymology
Origin of transpiration
1545–55; trans- + Latin spīrātiōn-, stem of spīrātiō breathing ( spīrāt ( us ), past participle of spīrāre to breathe + -iōn- -ion ); perhaps directly < French or New Latin
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Oxygen isotopes function as tracers, allowing scientists to learn about water sources, plant transpiration, and atmospheric moisture.
From Science Daily
As the air becomes hotter, it becomes easier for plants to lose water to transpiration, especially because photosynthesis occurs during daylight hours when temperatures are highest.
From Los Angeles Times
"We could exactly pinpoint how this is related to water transpiration and the ions the plant carries via the ascent of sap."
From Science Daily
ET includes evaporation from soil and open water pools such as lakes, rivers, and ponds, as well as transpiration from plant leaves.
From Science Daily
So, she compared transpiration in fallowed fields to active fields across the Central Valley.
From Science Daily
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
