EFFECTS OF BRASSINOSTEROIDS ON CONDITIONING AND GERMINATION OF CLOVERBROOMRAPE (OROBANCHE MINOR) SEEDS

Brassinolide [2 alpha, 3 alpha, oxy-24S-methyl-B-homo-7-oxa-alpha-chol estan-6-one] and its related compounds, brassinosteroids, applied at t he early stages of conditioning shortened the conditioning period requ ired before clover broomrape seeds would germinate after exposure to g ermination stimulants, such as dl-strigol and natural stimulants from red clover (Trifolium pratense L.) root exudate. Brassinosteroids appl ied after conditioning increased the rate of the seed germination indu ced by these stimulants. The inhibitory effect of light on seed germin ation when it was induced by dl-strigol could be overcome by brassinos teroids. Brassinosteroids also eliminated the inhibitory effects of li ght and dl-strigol applied at the early stages of conditioning. GA(3) was also effective in causing seed conditioning and increased the rate of the germination induced by these stimulants. There was a relations hip between brassinosteroids and GA(3) in many of the experiments cond ucted. These findings may have practical implications in increasing th e effectiveness of applying germination stimulants in the field to soi ls for 'suicidal germination' of broomrape seeds.