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Why do plants need water?.

Plants need large quantities of water for growth.  The most important factor driving water movement in plants is a process known as transpiration.  Transpiration is the loss of water from plants in the form of vapor (evaporation).  Plants utilize most of the water absorbed from the soil for transpiration (95%), but a small portion of the water absorbed is used during photosynthesis for producing the carbohydrates necessary for plant growth (5%).Water typically makes up 80 – 95% of the mass of growing plant tissues. Mature woody plant tissue water content ranges from 45 – 50% while herbaceous plant water content ranges from 70 – 95%.  Plants have cell walls that allow the build up of turgor pressure within each cell.  Turgor pressure contributes to rigidity and mechanical stability of non-woody plant tissue and is essential for many physiological processes including cell enlargement (plant growth), gas exchange in the leaves, transport of water and sugars, and many other processes.


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