pollen tube vs plant part

pollen tube and plant part both are nouns.

Word	Noun	Adjective	Verb	Adverb
pollen tube	Yes	No	No	No
plant part	Yes	No	No	No

As nouns, plant part is a hypernym of pollen tube; that is, plant part is a word with a broader meaning than pollen tube:

pollen tube: (botany) a slender tubular outgrowth from a pollen grain when deposited on the stigma for a flower; it penetrates the style and conveys the male gametes to the ovule
plant part: any part of a plant or fungus

Other hypernyms of pollen tube include plant structure.

pollen tube (noun)	plant part (noun)
(botany) a slender tubular outgrowth from a pollen grain when deposited on the stigma for a flower; it penetrates the style and conveys the male gametes to the ovule	any part of a plant or fungus