Plant sap
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:''"Sap" redirects here. For other uses see [[sap (disambiguation)]] or [[SAP_ERP]]''.
[[Image:Common jassid nymph feeding.jpg|thumb|250px|[[Leafhopper]]s and many other insects feed off plant sap]]
'''Sap''' is a [[fluid]] transported in [[xylem]] cells (tracheids or vessel elements) or [[phloem]] [[sieve tube element]]s of a [[plant]]. Fluid found in the vacuole of other cells is sometimes referred to as "cell sap". Other liquid compounds found in plants or exuded by plants, such as [[latex]], [[resin]]s, and [[mucilage]] are sometimes incorrectly referred to as sap.
Xylem sap consists primarily of water, with hormones, mineral elements, and other nutrients dissolved in the sap. Transport of sap in xylem is generally "[[basipetal]]", or upward from the roots toward the leaves. Over the past century, there has been some controversy regarding the mechanism of xylem sap transport, although most plant scientists today agree that the bulk of the evidence supports the [[cohesion-tension theory]] of xylem sap transport.
Phloem sap consists primarily of water, with sugars, hormones, and mineral elements dissolved in the sap. Phloem sap transport occurs from sources (a location where carbohydrates are produced or stored) toward sinks (a location where carbohydrates are utilized). The [[pressure flow hypothesis]] proposes a mechanism for phloem sap transport.
[[Maple syrup]] is made from reduced [[maple]] [[tree]] [[xylem]] sap. In some countries (e.g., [[Russia]] or [[Latvia]]) it is common to collect the early spring sap of [[birch]] trees (so called "birch juice") for human consumption; the sap can be used fresh or fermented. "Birch juice" is slightly sweet and very refreshing, but tends to become bitter in late spring; the rule of thumb is to collect it before any green leaves have appeared.
== See also ==
{{commonscat|Sap}}
* [[Latex]]
* [[Resin]]
[[Category:Plant physiology]]
[[Category:Trees]]
==References==
*Angeles, G., B.J. Bond, J.S. Boyer, T.J. Brodribb, J.R. Brooks, M.J. Burns, J.M. Cavender-Bares, M.J. Clearwater, H. Cochard, J.P. Comstock, S.D. Davis, J.-C. Domec, L.A. Donovan, F.W. Ewers, B.L. Gartner, U.G. Hacke, T.M. Hinckley, N.M. Holbrook, H.G. Jones, K.L. Kavanagh, B.E. Law, J. Lopez-Portillo, C. Lovisolo, T.A. Martin, J. Martinez-Vilalta, S. Mayr, F.C. Meinzer, P.J. Melcher, M. Mencuccini, S.S. Mulkey, A. Nardini, H. Neufeld, J.B. Passioura, W.T. Pockman, R.B. Pratt, S. Rambal, H. Richter, L. Sack, S. Salleo, A. Schubert, P.J. Schulte, J.P. Sparks, J.S. Sperry, R.O. Teskey, and M.T. Tyree. 2004. The cohesion-tension theory. ''New Phytologist'' 163:451-452.
* Raven, P.H., Evert, R.F. and Eichhorn, S.E. 1999. ''Biology of Plants''. W.H. Freeman.
* Taiz, L. and Zeiger, E. 1998. ''Plant Physiology''. Sinauer Associates, Sunderland, Mass.
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