The protective sheath that covers the first root of a grass or cereal grain seedling.
From Greek 'koleos' (sheath) + 'rhiza' (root). Like the coleoptile protects the first leaf, this structure was named for its sheath-like covering of the primary root in monocot seedlings.
Both the coleoptile and coleorhiza are unique to grasses and cereals, which is why wheat, rice, and corn seedlings can push through soil so effectively—they have two protective sheaths letting them power through tough conditions!
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