Taproot

n.

1.

(Bot.) The root of a plant which penetrates the earth directly downward to a considerable depth without dividing.

Noun	1.	taproot - (botany) main root of a plant growing straight downward from the stem
	2.	taproot - something that provides an important central source for growth or development; "the taproot of his resentment"; "genius and insanity spring from the same taproot"

beginning, bulb, bulbil, commencement, conception, corm, derivation, genesis, grass roots, head, inception, origin, original, origination, provenience, radical, radicle, radix, rhizome, rise, root, rootstock, source, stem, stock, tap, tuber, tubercle