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Transpiration of water in xylem Stoma in a tomato leaf shown via colorized scanning electron microscope The clouds in this image of the Amazon Rainforest are a result of evapotranspiration. Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers.
Transpiration can be regulated through stomatal closure or opening. It allows for plants to efficiently transport water up to their highest body organs, regulate the temperature of stem and leaves and it allows for upstream signaling such as the dispersal of an apoplastic alkalinization during local oxidative stress. Summary of water movement: Soil
At the same time evaporation from the soil surface is also substantial, the transpiration:evaporation ratio (T/ET) varying according to vegetation type and climate, peaking in tropical rainforests and dipping in steppes and deserts. [73] Transpiration plus evaporative soil moisture loss is called evapotranspiration.
Transpiration: the movement of water from root systems, through a plant, and exit into the air as water vapor. This exit occurs through stomata in the plant. Rate of transpiration can be influenced by factors including plant type, soil type, weather conditions and water content, and also cultivation practices. [ 6 ] :
Potential evapotranspiration is expressed in terms of a depth of water or soil moisture percentage. If the actual evapotranspiration is considered the net result of atmospheric demand for moisture from a surface and the ability of the surface to supply moisture, then PET is a measure of the demand side (also called evaporative demand).
Intrinsic water-use efficiency W i usually increases during soil drought, due to stomatal closure and a reduction in transpiration, and is therefore often linked to drought tolerance. Observatios from several authors [3] [6] [7] [8] have however suggested that WUE would rather be linked to different drought response strategies, where
The changes in soil moisture over time are known as soil moisture dynamics. Recent global studies using water stable isotopes show that not all soil moisture is equally available for groundwater recharge or for plant transpiration. [12] [13] Plant available water in sandy soils can be increased by the presence of sepiolite clay. [14]
Moisture stress is a form of abiotic stress that occurs when the moisture of plant tissues is reduced to suboptimal levels. Water stress occurs in response to atmospheric and soil water availability when the transpiration rate exceeds the rate of water uptake by the roots and cells lose turgor pressure.