flora vs phytoplankton

flora and phytoplankton both are nouns.

Word	Noun	Adjective	Verb	Adverb
flora	Yes	No	No	No
phytoplankton	Yes	No	No	No

As nouns, phytoplankton is a hyponym of flora; that is, phytoplankton is a word with a more specific, narrower meaning than flora:

flora: (botany) a living organism lacking the power of locomotion
phytoplankton: photosynthetic or plant constituent of plankton; mainly unicellular algae

flora (noun)	phytoplankton (noun)
(botany) a living organism lacking the power of locomotion	photosynthetic or plant constituent of plankton; mainly unicellular algae
all the plant life in a particular region or period