kernel vs plant structure

kernel and plant structure both are nouns.

Word	Noun	Adjective	Verb	Adverb
kernel	Yes	No	No	No
plant structure	Yes	No	No	No

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

kernel: the inner and usually edible part of a seed or grain or nut or fruit stone
plant structure: any part of a plant or fungus

Other hypernyms of kernel include plant part.

kernel (noun)	plant structure (noun)
the choicest or most essential or most vital part of some idea or experience	any part of a plant or fungus
a single whole grain of a cereal
the inner and usually edible part of a seed or grain or nut or fruit stone