In highly organized plants, vascular tissues (Xylem and Phloem) are the main components of transportation system. In general, xylem carries the water and minerals from roots to the aerial parts of the plants, whereas phloem carries food from leaves to other parts of the plants.
Xylem are lignified tissues and are characterized by tracheids and vessels. Evaporation of water from leaves (transpiration) creates a suction or pull that enables xylem to pull water from roots. Sometimes, the water may also move into roots due to osmosis and this will create a positive pressure on xylem to transport water. Xylem transports water and soluble nutrients, in response to transpirational pull and water osmosis, by capillary action and is capable of transporting water to great heights within tall plants.
Phloem are non-lignified tissues and transport soluble products of photosynthesis. They are characterized by living cells and transport the sugars by the process of translocation. Unlike xyle, phloem carries out multi-directional flow by using hydrostatic pressure.
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