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xylem |
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xylemTransport tissue found in vascular plants, whose main function is to conduct water and dissolved mineral nutrients from the roots to other parts of the plant. The water is ultimately lost by transpiration from the leaves (see leaf). Xylem is composed of a number of different types of cell, and may include long, thin, usually dead cells known as tracheids; fibres (schlerenchyma); thin-walled parenchyma cells; and conducting vessels. Transpiration is the loss of water, in the form of water vapour, from leaves of a plant to the air outside the leaf. The loss of water from the leaves drives the movement of water and minerals in the xylem. This is important because many plant cells need the minerals as nutrients. Xylem tissue is usually found close to the other transport tissue in plants, phloem, which transports sugars and amino acids (see protein). In non-woody plants phloem and xylem are found in bundles (called veins if they are in a leaf). In most angiosperms (flowering plants) water is moved through these vessels. Most gymnosperms and pteridophytes lack vessels and depend on tracheids for water conduction. Non-woody plants contain only primary xylem, derived from the procambium, whereas in trees and shrubs this is replaced for the most part by secondary xylem, formed by secondary growth from the actively dividing vascular cambium. The cell walls of the secondary xylem are thickened by a deposit of lignin, providing mechanical support to the plant; see wood. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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annual rings botany cambium phloem plant root root hair sclerenchyma secondary growth tracheid transpiration transport vascular bundle vein water wood | When the flower is connected to the plant, the Xylem is continuous and draws water from the root. The tree takes it up through the roots or inside the xylem, and it goes through the leaves and bark. WATER TRANSPORT RELATIONSHIPS BETWEEN THE SOIL, PLANT, AND ATMOSPHERE The long-distance transport of liquids in high plants includes the ground water suction by roots; upward transport of the solution (xylem sap) along the xylem pathways from the roots to leaves; water evaporation by the leaves; downward transport of the assimilates produced by photosynthetic cells (phloem sap) along the phloem pathways from the leaves to the growing organs, flowers, fruit, and roots (Fig. |
xylem |
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