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protophloem
protophloem n.
Brit. 
/ˌprəʊtə(ʊ)ˈfləʊɛm/
, /ˌprəʊtə(ʊ)ˈfləʊɛm/U.S. /ˌproʊdoʊˈfloʊˌɛm/
[after German Protophloëm (E. Russow 1873, in Mém. Acad. Impér. Sci. St.-Pétersbourg (Sér. 7) 19 4)] Botany the first-formed elements of the primary phloem, the cells of which mature before the elongation of the surrounding plant tissue; cf. metaphloem n./ˌproʊdoʊˈfloʊˌɛm/ΘΚΠ
the world > plants > part of plant > cell or aggregate tissue > [noun] > tissue > xylem or phloem
liber1753
phloem1872
xylem1875
protophloem1884
protoxylem1887
internal phloem1891
metaxylem1894
hadrome1898
leptome1898
metaphloem1900
included phloem1910
1884 F. O. Bower & D. H. Scott tr. H. A. de Bary Compar. Anat. Phanerogams & Ferns 390 The first primitive elements of the phloem, Russow's protophloem.
1953 K. Esau Plant Anat. xii. 286 The primary phloem may be divided into protophloem and metaphloem.
2001 Genes & Devel. 15 264/1 The transition of protophloem cells to mature phloem in roots involves the formation of a sieve plate and occurs in the region of the maximum growth rate.
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