What is Xylem?
[[File:The Oak (Marshall Ward) Fig 16.jpg|thumb|right|Xylem cells are long and narrow, like [[Pipe (material)|pipes]], and they carry water]] [[File:MAGNIFICATION OF PHLOEM OR XYLEM TUBES IN DOUGLAS FIR WOOD TAKEN THROUGH A MICROSCOPE IN NEW WESTMINSTER, BRITISH... - NARA - 555171.jpg|thumb|right|When a tree is cut across, the xylem cells can be seen under a [[microscope]]. When cut that way, they look like small circles.]] '''Xylem''' is a [[tissue (biology)|tissue]] in [[vascular plant]]<nowiki/>s. Its [[cell]]s have thick, hard walls. Xylem tissue dies soon after it is formed and is the [[wood]] in the middle of a tree. The dead cells are like [[Pipe (material)|pipes]], hollow and rigid. Xylem is one of two tissues in the plant which [[transportation|transport]] substances that plants need to live. Substances that xylem transports include water and minerals obtained through the plant's roots, as xylem runs from the [[root]]s to the [[Plant stem|stems]] and [[leaf|leaves]]. The other transport tissue is the [[phloem]], which transports energy in the form of [[sugar]] (as well as any other chemicals) from the leaves to the rest of the plant. Xylem [[cell]]s are present in all parts of a plant, in stems, roots, and leaves. Water is carried against [[gravity]] by the negative pressure that builds up through the process of [[transpiration]], which is the evaporation of moisture in leaves. Xylem consists of four types of cells: # Xylem parenchyma which are living cells with thin walls # Xylem fibres # [[Tracheids]] # [[Xylem vessels]] Most of these cells are dead cells and have thick walls. ==Related pages== * [[Medullary ray]] {{-}} {{biology-stub}} [[Category:Vascular tissue]] [[Category:Plant physiology]]