protoxylem

[proh-tuh-zahy-luhm, -lem]

noun

Botany.

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

protoxylem

/ ˌprəʊtəˈzaɪləm /

noun

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

protoxylem

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

Word History and Origins

Origin of protoxylem¹

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.

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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.

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

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

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