Definition of radicles:
(n) :
(botany) The rudimentary shoot of a plant which supports the cotyledons in the seed, and from which the root is developed downward; the root of the embryo.
(n) :
(botany) A rootlet.
(n) :
(chemistry) Archaic form of radical. [(historical, 19th-century Britain, politics) A member of the most progressive wing of the Liberal Party; someone favouring social reform (but generally stopping short of socialism).]