floral envelope vs plant organ

floral envelope and plant organ both are nouns.

Word	Noun	Adjective	Verb	Adverb
floral envelope	Yes	No	No	No
plant organ	Yes	No	No	No

As nouns, plant organ is a hypernym of floral envelope; that is, plant organ is a word with a broader meaning than floral envelope:

floral envelope: collective term for the outer parts of a flower consisting of the calyx and corolla and enclosing the stamens and pistils
plant organ: a functional and structural unit of a plant or fungus

Other hypernyms of floral envelope include cover, covering, natural covering.

floral envelope (noun)	plant organ (noun)
collective term for the outer parts of a flower consisting of the calyx and corolla and enclosing the stamens and pistils	a functional and structural unit of a plant or fungus