Suppression of stem growth in pot kalanchoe ‘Gold Strike’ by recycled subirrigational supply of plant growth retardants

Abstract

Effect of concentration of paclobutrazol and uniconazole supplied to the recycling nutrient solution in an ebb 
and flow system on the growth and flowering of kalanchoe cultivar ‘Gold Strike’ was examined. Plants potted in 
10 cm (370 mL) pots were supplied with a nutrient solution containing 80 mL per pot of 0.5, 1.0, or 2.0 mg ּL-1 
paclobutrazol or of 0.125, 0.250, or 0.50 mg ּL-1 uniconazole. Plants were irrigated five times during the 
reproductive short day treatment period. During each irrigation, the nutrition solution was filled to a depth of 2 
cm above the pot base and was left for about 15 min before drainage to reservoir. The control treatment, a foliar 
spray of 240 mL ּm-2 of 10 mg L-1 placlobutrazol or 2.5 mg ּL-1 uniconazole was applied twice after pinching at 
one week interval. At all applied concentrations, plant size, flower stem length and stem diameter decreased as 
compared to the control. However, the number of florets increased in the treated plants. Results indicate that 
the subirrigational optimum concentration was 
0.5 mg ּL-1 paclobutrazol and 0.125 mg ּL-1 uniconazole is 
comparable to foliar spray. Therefore, subirrigational application of growth retardants at lower concentrations 
could be used as an effective mean for suppressing stem growth. More uniform and environmentally sound 
application of growth retardants with the same effectiveness could be achieved.