Sap

Source: Wikipedia, the free encyclopedia.
For other uses, see Sap (disambiguation) and SAP (disambiguation).
"Saps" redirects here. Not to be confused with SAPS.
Sap droplets of Dracaena trifasciata

Sap is a fluid transported in xylem cells (vessel elements or tracheids) or phloem sieve tube elements of a plant. These cells transport water and nutrients throughout the plant.

Sap is distinct from

cell sap
; it is a separate substance, separately produced, and with different components and functions.

Insect honeydew is called sap, particularly when it falls from trees, but is only the remains of eaten sap and other plant parts.[1]

Types of sap

Saps may be broadly divided into two types: xylem sap and phloem sap.

Xylem sap

Xylem sap (pronounced

mineral elements and other nutrients. Transport of sap in xylem is characterized by movement from the roots toward the leaves.[2]

Over the past century, there has been some controversy regarding the mechanism of xylem sap transport; today, most plant scientists agree that the

cohesion-tension theory best explains this process, but multiforce theories that hypothesize several alternative mechanisms have been suggested, including longitudinal cellular and xylem osmotic pressure gradients, axial potential gradients in the vessels, and gel- and gas-bubble-supported interfacial gradients.[3][4]

Xylem sap transport can be disrupted by cavitation—an "abrupt phase change [of water] from liquid to vapor"[5]—resulting in air-filled xylem conduits. In addition to being a fundamental physical limit on tree height, two environmental stresses can disrupt xylem transport by cavitation: increasingly negative xylem pressures associated with water stress, and freeze-thaw cycles in temperate climates.[5]

Phloem sap

Phloem sap (pronounced

macromolecules as they pass through plasmodesmata.[6]

Leafhoppers feeding on sap, attended by ants

Many insects of the

oligosaccharides."[7]
A much larger set of animals do however consume phloem sap by proxy, either "through feeding on the honeydew of phloem-feeding hemipterans. Honeydew is physiologically less extreme than phloem sap, with a higher essential/non-essential amino acid ratio and lower osmotic pressure,"[7] or by feeding on the biomass of insects that have grown on more direct ingestion of phloem sap.

Human uses

sugar maple xylem sap.[8] The sap often is harvested from the sugar maple, Acer saccharum.[9]

In some countries (e.g.,

fermented and contains xylitol.[10]

Certain palm tree sap can be used to make

Chilean wine palm to make their syrup called miel de palma.[citation needed
]

See also

References

  1. ^ "How to Remove Tree Sap From a Car". HowStuffWorks. 20 August 2019. Retrieved 23 December 2020.
  2. ISBN 978-3-642-68887-4
    .
  3. PMID 12060254
    .
  4. doi:10.1093/jxb/48.10.1753
    .
  5. ^
    JSTOR 1939633. Archived from the original
    (PDF) on 2017-08-10. Retrieved 2018-12-18.
  6. ^ a b Turgeon, Robert; Wolf, Shmuel (2009). "Phloem Transport: Cellular Pathways and Molecular Trafficking". Annual Review of Plant Biology. 60 (1): 207–21.
    PMID 19025382
    .
  7. ^ a b c Douglas, A.E. (2006). "Phloem-sap feeding by animals: problems and solutions". Journal of Experimental Botany. 57 (4): 747–754.
    PMID 16449374
    .
  8. ^ Saupe, Stephen. "Plant Physiology". College of Saint Benedict and Saint John's University. Retrieved 3 April 2018.
  9. ^ Morselli, Mariafranca; Whalen, M Lynn (1996). "Appendix 2: Maple Chemistry and Quality". In Koelling, Melvin R; Heiligmann, Randall B (eds.). North American Maple Syrup Producers Manual. Bulletin. Vol. 856. Ohio State University. Archived from the original on 29 April 2006. Retrieved 20 September 2010.
  10. ISBN 978-1-4020-4992-7. Archived
    from the original on 23 November 2017. Retrieved 6 April 2013.

External links

  • Media related to Plant sap at Wikimedia Commons
Retrieved from "https://en.wikipedia.org/w/index.php?title=Sap&oldid=1216665577"
This page is based on the copyrighted Wikipedia article: Sap. Articles is available under the CC BY-SA 3.0 license; additional terms may apply.Privacy Policy