WordNet records no synonym and no antonym for corolla. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
(botany) the whorl of petals of a flower that collectively form an inner floral envelope or layer of the perianth
“we cultivate the flower for its corolla”
Synonyms, antonyms and the broader and narrower relations for corolla come from Princeton University’s WordNet. Full sources and licences.