Plants {woody plant} can have tough, thick, hard stem. Stem is hard because it has lignin.
Woody plants {perennial} can live longer than one year.
Rare plants {monocarpic plant} flower only once and live from 2 to 100 years.
Some perennial plants {shrub}| have many similar woody stems.
Some perennial plants {tree, stem}| have one main woody stem.
In perennials, stem xylem and phloem grow each summer and stop growing in winter, so years leave distinct rings {annual ring}| underneath cortex.
Outer xylem layers {sapwood}| conduct sap.
Inner xylem layers {heartwood}| are for strength.
4-Botany-Plant-Vascular-Parts-Stem
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Date Modified: 2022.0225