protoxylem
noun
pro·to·xy·lem
ˌprō-tə-ˈzī-ləm 
-ˌlem
: the first-formed xylem developing from procambium and consisting of narrow cells with annular, spiral, or scalariform wall thickenings
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“Protoxylem.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/protoxylem. Accessed 10 Jul. 2025.
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