What is "brassinosteroid"

n. (context steroid English) Any of a family of steroidal plant hormones produced by members of the genus ''Brassica''; the brassins

Brassinosteroids (BRs) are a class of polyhydroxysteroids that have been recognized as a sixth class of plant hormones. These were first explored nearly 40 years ago, when Mitchell et al. reported promotion in stem elongation and cell division by the treatment of organic extracts of rapeseed ( Brassica napus) pollen. Brassinolide was the first isolated brassinosteroid in 1979, when pollen from Brassica napus was shown to promote stem elongation and cell divisions, and the biologically active molecule was isolated. The yield of brassinosteroids from 230 kg of Brassica napus pollen was only 10 mg. Since their discovery, over 70 BR compounds have been isolated from plants.