order Graminales vs plant order

order Graminales and plant order both are nouns.

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

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

order Graminales (noun)	plant order (noun)
grasses, sedges, rushes	the order of plants