order Xyridales vs plant order

order Xyridales and plant order both are nouns.

Word	Noun	Adjective	Verb	Adverb
order Xyridales	Yes	No	No	No
plant order	Yes	No	No	No

As nouns, plant order is a hypernym of order Xyridales; that is, plant order is a word with a broader meaning than order Xyridales:

order Xyridales (noun)	plant order (noun)
an order of monocotyledonous herbs	the order of plants