Brassinosteroids are a new class of plant hor-mones with the A-D ring structure of steroids to which an alkyl side chain is attached. A great number of BRs occur in plants, with the most potent substances being brassinolide and castasterone. BRs are widely distrib- uted throughout the plant kingdom. They are present in nearly all parts and organs in flowering plants, with the highest concentrations is found in pollen grains and in immature seeds. To date, 42 brassinosteroids and four brassinosteroid conjugates have been characterized (Rao et al., 2002). BRs have served multi-functions in plant growth and development as well as other plant hormones. They perform their physiological roles in various plants like cell elongation, swelling, curvature,
germination of seed, floral stimulation, senescence,stress tolerance and increasing yield. BRs have been considered as promising compounds for application both in molecular level and physiological level. Since BRs have a broad spectrum of stimulative and protective activities that have a positive effects on the quantity and quality of crops, the possibility of using them as a plant growth regulator to enhance yield in other crops is likely. New discoveries of the physiological properties of BRs pave us to recognize them as highly promis-ing natural substances suitable for broad application in
agriculture. Even though, one of the major constraints to employ BRs in large scale in fields was reported by Rao et al (2002) is their higher costs.