pea plant vs leguminous plant

pea plant and leguminous plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
pea plant	Yes	No	No	No
leguminous plant	Yes	No	No	No

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

pea plant: a leguminous plant of the genus Pisum with small white flowers and long green pods containing edible green seeds
leguminous plant: an erect or climbing bean or pea plant of the family Leguminosae

Other hypernyms of pea plant include legume.

pea plant (noun)	leguminous plant (noun)
a leguminous plant of the genus Pisum with small white flowers and long green pods containing edible green seeds	an erect or climbing bean or pea plant of the family Leguminosae