plant material vs straw

plant material and straw both are nouns.

Word	Noun	Adjective	Verb	Adverb
plant material	Yes	No	No	No
straw	Yes	Yes	Yes	No

As nouns, straw is a hyponym of plant material; that is, straw is a word with a more specific, narrower meaning than plant material:

plant material: material derived from plants
straw: material consisting of seed coverings and small pieces of stem or leaves that have been separated from the seeds

Other hyponyms of plant material include cutin, chaff, husk, shuck, stalk, stubble, cork, plant product, vegetable tallow, wood.

plant material (noun)	straw (noun)
material derived from plants	a thin paper or plastic tube used to suck liquids into the mouth
	a variable yellow tint; dull yellow, often diluted with white
	plant fiber used e.g. for making baskets and hats or as fodder
	material consisting of seed coverings and small pieces of stem or leaves that have been separated from the seeds

plant material (adjective)	straw (adjective)
	of a pale yellow color like straw; straw-colored

plant material (verb)	straw (verb)
	spread by scattering ("straw" is archaic)
	cover or provide with or as if with straw