water trumpet vs water plant

water trumpet and water plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
water trumpet	Yes	No	No	No
water plant	Yes	No	No	No

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

water trumpet: any plant of the genus Cryptocoryne; evergreen perennials growing in fresh or brackish water; tropical Asia
water plant: a plant that grows partly or wholly in water whether rooted in the mud, as a lotus, or floating without anchorage, as the water hyacinth

Other hypernyms of water trumpet include aquatic plant, hydrophyte, hydrophytic plant.

water trumpet (noun)	water plant (noun)
any plant of the genus Cryptocoryne; evergreen perennials growing in fresh or brackish water; tropical Asia	a plant that grows partly or wholly in water whether rooted in the mud, as a lotus, or floating without anchorage, as the water hyacinth