protoxylem

American  

[proh-tuh-zahy-luhm, -lem] / ˌproʊ təˈzaɪ ləm, -lɛm /

noun

Botany.

1. the part of the primary xylem that develops first, consisting of narrow, thin-walled cells.

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protoxylem British  

/ ˌprəʊtəˈzaɪləm /

noun

1. the first-formed xylem tissue, consisting of extensible thin-walled cells thickened with rings or spirals of lignin Compare metaxylem

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protoxylem Scientific  

/ prō′tə-zī′ləm /

1. The first formed xylem that differentiates from the procambium.

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Etymology

Origin of protoxylem

First recorded in 1895–1900; proto- + xylem

Example Sentences

Kondo, Y., Hirakawa, Y., Kieber, J. J. & Fukuda, H. CLE peptides can negatively regulate protoxylem vessel formation via cytokinin signaling.

From Nature

In a bundle examined in the basal portion of a leaf the bulk of the xylem is found to be centrifugal in position, but internally to the protoxylem there is a group of centripetal tracheids; higher up in the petiole the xylem is mainly centripetal, the centrifugal wood being represented by a small arc of tracheids external to the protoxylem and separated from it by a few parenchymatous elements.

From Project Gutenberg

Finally, in the pinnae of the frond the centrifugal xylem may disappear, the protoxylem being now exarch in position and abutting on the phloem.

From Project Gutenberg

Cortex; en. endodermis; pe. pericycle; ph. phloëm; pr. protoxylem; xy. xylem vessel.

From Project Gutenberg