leafage vs plant organ

leafage and plant organ both are nouns.

Word	Noun	Adjective	Verb	Adverb
leafage	Yes	No	No	No
plant organ	Yes	No	No	No

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

leafage: the main organ of photosynthesis and transpiration in higher plants
plant organ: a functional and structural unit of a plant or fungus

leafage (noun)	plant organ (noun)
the main organ of photosynthesis and transpiration in higher plants	a functional and structural unit of a plant or fungus