Effect of the growth retardant Cycocel® in controlling the growth of Dombeya burgessiae

Pink dombeya (Dombeya burgessiae) was tested for its potential as a flowering potted plant, using the growth retardant Cycocel (R) (2-chloroethyl)-trimethylammonium chloride. The treatments included a control, 0.5, 1, 2 and 3 mg/L of Cycocel (R) per pot and were applied when seedlings reached 7 - 8 cm in height. All treatments significantly reduced plant height. The plants treated with 0.5 mg/L were only marginally shorter than the control, while the height of plants treated with 1, 2 and 3 mg/L Cycocel (R), were greatly reduced. Increased Cycocel (R) concentrations decreased plant width in all treatments, as compared with the control. At all applied concentrations, the deterioration of foliage greenness was observed. The highest concentration of Cycocel (R) (3 mg/L) resulted in cycocel-induced chlorosis. This was followed by the 2, 1 and 0.5 mg/L respectively, all showing symptoms of chlorosis; however to a lesser extent. Cycocel (R) treated plants exhibited greener foliage in the new leaves formed in the weeks after application compared with the control. It is important to mention that the new leaves formed in the weeks after application were not affected, and were in fact darker green with the higher concentrations of Cycocel (R) treatments. The fresh and dry weights of plants severely decreased with the increased Cycocel (R) concentrations. The highest concentration (0.3% a.i.) caused the largest reduction, with plants in this treatment only weighing 38% of the total fresh weight of the control and 35% of the total dry weight.