Phloem

Phloem (/ˈfloʊ.əm/, FLOH-əm) is the living tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as photosynthates, in particular the sugar sucrose,^[1] to the rest of the plant. This transport process is called translocation.^[2] In trees, the phloem is the innermost layer of the bark, hence the name, derived from the Ancient Greek word φλοιός (phloiós), meaning "bark".^[3]^[4] The term was introduced by Carl Nägeli in 1858.^[5]^[6] Different types of phloem can be distinguished. The early phloem formed in the growth apices is called protophloem. Protophloem eventually becomes obliterated once it connects to the durable phloem in mature organs, the metaphloem.^[7]^[8] Further, secondary phloem is formed during the thickening of stem structures.^[9]

^ Lalonde S. Wipf D., Frommer W. B. (2004). "Transport mechanisms for organic forms of carbon and nitrogen between source and sink". Annu Rev Plant Biol. 55: 341–72. doi:10.1146/annurev.arplant.55.031903.141758. PMID 15377224.
^ Collins Edexcel International GCSE Biology, Student Book (ISBN 978-0-00-745000-8) p.124
^ Harper, Douglas. "phloem". Online Etymology Dictionary.
^ φλοιός. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project.
^ Nägeli, Carl (1858). "Das Wachstum des Stammes und der Wurzel bei den Gefäßpflanzen und die Anordnung der Gefäßstränge im Stengel" [The growth of the stem and of the root among vascular plants and the arrangement of the vascular strands in the stalk]. Beiträge zur Wissenschaftlichen Botanik (Contributions to Scientific Botany) (in German). 1: 1–156. From p. 9: "Ich will die beiden Partien Dauergewebe, welche von dem Cambium nach aussen und nach innen gebildet werden, Phloëm und Xylem nennen." (I will call the two parts of the permanent tissue, which are formed by the cambium outwardly and inwardly, "phloëm" and "xylem".)
^ Buvat, Roger (1989). "Phloem". Ontogeny, Cell Differentiation, and Structure of Vascular Plants. pp. 287–368. doi:10.1007/978-3-642-73635-3_10. ISBN 978-3-642-73637-7.
^ Graeff, Moritz; Hardtke, Christian S. (2021). "Metaphloem development in the Arabidopsis root tip". Development. 148 (18). doi:10.1242/dev.199766. PMID 34224570.
^ Evert, Ray F. (2006-08-25). Esau's Plant Anatomy: Meristems, Cells, and Tissues of the Plant Body: Their Structure, Function, and Development (1 ed.). Wiley. doi:10.1002/0470047380. ISBN 978-0-471-73843-5.
^ Nieminen, Kaisa; Blomster, Tiina; Helariutta, Ykä; Mähönen, Ari Pekka (May 2015). "Vascular Cambium Development". The Arabidopsis Book. 2015 (13): e0177. doi:10.1199/tab.0177. ISSN 1543-8120. PMC 4463761. PMID 26078728.

[1] Lalonde S. Wipf D., Frommer W. B. (2004). "Transport mechanisms for organic forms of carbon and nitrogen between source and sink". Annu Rev Plant Biol. 55: 341–72. doi:10.1146/annurev.arplant.55.031903.141758. PMID 15377224.

[2] Collins Edexcel International GCSE Biology, Student Book (ISBN 978-0-00-745000-8) p.124

[3] Harper, Douglas. "phloem". Online Etymology Dictionary.

[4] φλοιός. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project.

[5] Nägeli, Carl (1858). "Das Wachstum des Stammes und der Wurzel bei den Gefäßpflanzen und die Anordnung der Gefäßstränge im Stengel" [The growth of the stem and of the root among vascular plants and the arrangement of the vascular strands in the stalk]. Beiträge zur Wissenschaftlichen Botanik (Contributions to Scientific Botany) (in German). 1: 1–156. From p. 9: "Ich will die beiden Partien Dauergewebe, welche von dem Cambium nach aussen und nach innen gebildet werden, Phloëm und Xylem nennen." (I will call the two parts of the permanent tissue, which are formed by the cambium outwardly and inwardly, "phloëm" and "xylem".)

[6] Buvat, Roger (1989). "Phloem". Ontogeny, Cell Differentiation, and Structure of Vascular Plants. pp. 287–368. doi:10.1007/978-3-642-73635-3_10. ISBN 978-3-642-73637-7.

[7] Graeff, Moritz; Hardtke, Christian S. (2021). "Metaphloem development in the Arabidopsis root tip". Development. 148 (18). doi:10.1242/dev.199766. PMID 34224570.

[8] Evert, Ray F. (2006-08-25). Esau's Plant Anatomy: Meristems, Cells, and Tissues of the Plant Body: Their Structure, Function, and Development (1 ed.). Wiley. doi:10.1002/0470047380. ISBN 978-0-471-73843-5.

[9] Nieminen, Kaisa; Blomster, Tiina; Helariutta, Ykä; Mähönen, Ari Pekka (May 2015). "Vascular Cambium Development". The Arabidopsis Book. 2015 (13): e0177. doi:10.1199/tab.0177. ISSN 1543-8120. PMC 4463761. PMID 26078728.

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