Primary roots: comparison with stem anatomy

Identifying Stems and Roots

Diagnostic:

	stem	root
primary phloem and primary xylem	on the same ray	on separate rays
protoxylem and metaxylem	endarch	exarch

Characteristic:

	stem	root
pith and cortex	small relative to pith	pith small or absent

It is important the you are able to differentiate between characteristic and diagnostic features. Which would you rely on most to make up your mind as to whether you were looking at a stem or a root?