Cotyledon of maize grain is called:

In maize grains, the single large shield-shaped cotyledon is called scutellum. The scutellum is believed to contain an as yet unidentified protein transporter that facilitates starch movement from the endosperm to the embryo.

Coleoptile is a sheath-like structure that protects the young shoot tip in monocots.

Coleorhiza is another sheath-like structure that protects the young root tip in monocots.

Plumule is the rudimentary shoot or stem of an embryo plant.