How does a plant grow taller and also thicker — is it the same tissue doing both?
No, two different meristems do the two jobs.
No, two different meristems do the two jobs. The apical meristems at the tips of shoots and roots divide to add length, making the plant taller and its roots deeper (primary growth). The lateral meristem (vascular cambium) divides sideways to add new xylem and phloem, thickening the stem and trunk year after year (secondary growth). Length and girth come from separate growth zones.
Key point
Apical meristem adds length (height); lateral cambium adds girth (thickness).
Common mistake
assuming one growth region handles both height and width.
Memory tip
tips lengthen the plant; the cambium fattens it.
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