How a stem and a root grow thicker. The vascular cambium and the cork cambium, annual rings, heartwood and sapwood, and the bark and lenticels of a tree.
3 lessons, about 1 h 15 min3 simulations10 problems3 practice questionsPython in every lesson
Created by StemPy LabDicot stems and roots grow thicker through the vascular cambium. Fascicular and interfascicular cambium join into a ring. It cuts secondary xylem inward and secondary phloem outward, and makes more xylem than phloem. Monocots have no cambium.
As a stem thickens, the cork cambium makes cork outward and phelloderm inward. Together with the cork cambium these form the periderm. Lenticels are gaps in the cork that let air pass. Bark is everything outside the vascular cambium.
Spring wood is light, with wide vessels. Autumn wood is dark, with narrow vessels. A pair of them makes one annual ring, and counting rings gives the age of a tree. The old inner wood becomes dark, dead heartwood, and the outer sapwood carries the water.
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