Vascular plant parts {stem, plant}| can connect roots to leaves. Dicots have three stem layers: central pith, vascular-bundle ring, and outer cortex. Stem pith stores food. Stem vascular bundles have cambium to heal plant wounds. Stem cortex has dead-cell outer layer and live-cell inner layer. Monocots have epidermis, stomata, vascular bundles throughout stem, no pith, and surface cortex cells with thick cell-wall layers.
Plants can have bark swellings {lenticel}, which allow air diffusion.
Stems have growing points {node, stem} for flowers and leaves.
Central soft stem parts {pith}| have fundamental plant tissue.
Stems can have woody sharp points {thorn}|.
Underground stems can have bulb-like regions {corm}.
Ferns and grasses have underground stems {rhizome}|.
Plants can have long horizontal ground stems {stolon}.
Some rhizomes {tuber, root}| store starch.
Plants {herbaceous plant} {herb, stem}| can have soft, green, thin stems.
Herbaceous plants {annual}| can live one season, from early spring to late autumn.
Herbaceous plants {biennial}| can live between twelve and twenty-four months.
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.
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Date Modified: 2022.0225