Phytomer

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Phytomers are the repeating building blocks of a plant. Each phytomer includes a node with a leaf and an accompanying bud, plus a small piece of stem, and they’re continually produced by growth regions at the tips of roots and shoots during the plant’s life. The speed at which leaves appear on a shoot is called the phyllochron, while the plastochron is the speed at which new leaf primordia (the beginnings of leaves) are formed. The plastochron is usually faster than the phyllochron, meaning many leaf primordia begin forming before older leaves are fully developed. In young plants, phytomer production starts at the apical (tip) meristems, but as the plant grows, secondary (lateral) meristems also begin producing phytomers along the sides.