Causes of Centrifugal Root Promotion

Role of water in centrifugal root promotion, effect of centrifugation on ethylene concentration of cuttings, and effect of ethylene on root formation were investigated using Salix jragilis softwood cuttings. When cuttings were centrifuged with water, more roots formed with increasing water depth. Soaking of cuttings upright in water for 24 h stimulated root formation and produced more roots as the depth of water was increased, with submerged cuttings producing the highest number of roots. Soaking of cuttings upright in hot water for 1 h also stimulated root formation with the best root formation occurring at 40°C. Submerging in, or centrifuging with water increased ethylene concentration in cuttings. Ethylene gas and Ethrel treatments stimulated root formation. It is suggested that submerging in water increases the ethylene concentration in Salix fragilis softwood cuttings which in turn stimulates root formation of the cuttings. Centrifuging cuttings with water increased water content of the cuttings. It is suggested that this increase in water content plays a role similar to the submersion of cuttings as described above.