Effect of plant growth retardants on the growth charactelistics of potted Spathiphyllum in an ebb and flow system

Abstract

Effect of concentrations of plant growth retardants (PGRs) supplied to a recirculated nutrient solution in an ebb and flow system on the growth characteristics of potted Spathiphyllum 'Top-Pin' and 'Mini' was examined. Plants were planted in 10 cm plastic pots, containing a mixture of peat moss and perlite (1:1, v/v) on 29 Mar. 2006 and were grown until 27 Feb. 2007. The PGRs used were 0.5, 1.0, 1.5, 2.0 mg . L-1 paclobutrazol (Boundy), 300, 400, 500, 600 mg.L-1 CCC (Cycocel), and 10, 15, 20, 25 mg.L-1 ethephon (Florel). Plant height decreased by all PGRs tested. Paclobutrazol was the most effective in inhibition of plant height, plant width, and petiole length. The effect increased with increasing paclobutrazol concentration, accompanied with increasing chlorophyll contents, leaf length, and leaf area. However, paclobutrazol caused phytotoxicity, when applied at a 2.0 mg.L-1 concentration. Treatment of CCC reduced plant height, but produced phytotoxic symptorns and even plant death, especially at high concentrations. All concentrations of ethephon gave a minor effect on growth, and 'Top-Pin' at 25 mg.L-1 and 'Mini' at 20 mg.L-1 treatments resulted in the greatest reduction of plant height and leaf width. 'Mini' was more sensitive than 'Top-Pin' in all treatments. The results suggested that paclobutrazol is the most suitable PGR among the tested PGRs to produce a potted Spathiphyllum in a recirculation ebb and flow system.