A portion of meristem (PO:0009013) tissue located parallel to the sides of a shoot axis (PO:0025029) or root (PO:0009005) that participates in lateral growth. [source: ISBN:047125208]
Comment
A term for lateral growth has been requested in GO. Lateral meristems contribute to an increase in the cross-sectional area of a shoot axis or root. Examples of lateral meristems are: cambium (PO:0005597) (includes cork cambium (PO:0005599) and vascular cambium (PO:0005598)), shoot lateral meristem (PO:0006344) (includes primary thickening meristem (PO:0005039)), root lateral meristem (PO:0006308), and secondary thickening meristem (PO:0025414). Contrasts with apical meristem (PO:0020144), phyllome marginal meristem (PO:0025404), or intercalary meristem (PO:0006073).