Water Movement
Plants that grow on land (terrestrial plants) find the materials they require for life in two different locations. The soil is the source of water and minerals to be used for a variety of functions, while the atmosphere provides carbon dioxide for photosynthesis. The root system takes up water and minerals from the soil, while the shoot system, consisting of leaves and stems, carries out photosynthesis. As larger plants evolved, the roots and shoots became increasingly distant from each other, and long-distance transport systems (xylem and phloem) became necessary for survival. Clearly, one of the most important functions of the root system is the absorption of water.How does the root absorb water? Once inside the plant, how do water and dissolved minerals move from the root to the shoot? What happens to the water once it is delivered to the leaves by the xylem? To answer these questions, it is useful to discuss the end of the transport process first, since it is there that the driving force is found.
Transpiration
Nearly 99 percent of the water taken up by plants is lost to the atmosphere through small pores located mainly on the lower surface of leaves.
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