XVI International Botanical Congess

We studied hormonal regulation of photomorphogenesis using cucumber seedlings with brassinosteroid-biosynthesis-specific inhibitor, Brassinazole (Brz). When seedlings were germinated in the dark in half MS agar medium containing Brz, cotyledon opening was observed with inhibited hypocotyl elongation. However, when they were germinated in distilled water, agar or soil containing Brz in the dark, neither hook unfolding nor cotyledon opening was observed. In contrast, cytokinin treatment caused both of them in any of these growth conditions. We analyzed endogenous Brs for light- and dark-grown seedlings by GC-MS. Light-grown plants accumulated more castasterone than dark-grown ones. Based on these observations, we will discuss on the hormonal regulation of photomorphogenesis.