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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.
The ocean plays a key role in the water cycle as it is the source of 86% of global evaporation. [2] The water cycle involves the exchange of energy, which leads to temperature changes. When water evaporates, it takes up energy from its surroundings and cools the environment. When it condenses, it releases energy and warms the environment.
This means water moves up the vessels. The last stage in the transpiration stream is the water moving into the leaves, and then the actual transpiration. First, the water moves into the mesophyll cells from the top of the xylem vessels. Then the water evaporates out of the cells into the spaces between the cells in the leaf.
Rate of transpiration can be influenced by factors including plant type, soil type, weather conditions and water content, and also cultivation practices. [6]: Ch. 1, "Transpiration" Evapotranspiration is typically measured in millimeters of water (i.e. volume of water moved per unit area of the Earth's surface) in a set unit of time. [6]:
Of the 150 kWh falling on the crown, 1% is used for photosynthesis, 10% reflected as light energy, 5 to 10% as sensible heat with the remaining 79 to 84% entering the process of transpiration. [ 3 ] If a larger tree has a sufficient water supply, it can evaporate more than 100 L of water a day.
The following is a breakdown of the energetics of the photosynthesis process from Photosynthesis by Hall and Rao: [6]. Starting with the solar spectrum falling on a leaf, 47% lost due to photons outside the 400–700 nm active range (chlorophyll uses photons between 400 and 700 nm, extracting the energy of one 700 nm photon from each one)
A drop of water can be in the ocean for years, or evaporate after a few days. Water is constantly changing and moving forms. Climate change can alter the life of a drop of water. With global warming, water evaporates faster and the cycle keeps moving at faster rates. The key here is the water cycle and how this works on a daily basis. [4]
Since liquid water flows, ocean waters cycle and flow in currents around the world. Since water easily changes phase, it can be carried into the atmosphere as water vapour or frozen as an iceberg. It can then precipitate or melt to become liquid water again. All marine life is immersed in water, the matrix and womb of life itself. [7]