Response of Dendranthema grandiflora (Ramat) to three plant growth regulators in container paint mix applications

The effectiveness of plant growth regulators (PGRs) when applied in a paint mix to the inside of containers was evaluated. Two kinds of paint (regular flat latex and SpinOut^®) were evaluated for their respective effectiveness with three separate plant growth regulators (paclobutrazol, uniconazole, and ancymidol) on the growth of Dendranthema grandiflora (Ramat) (cv. Fina and Pelee) plants. Chrysanthemums grown in containers were subjected to three different application methods: interior surfaces covered by a mixture of paint and plant growth regulator (PGR) and soil drench or spray treatments according to label recommendations. The effect of composted pine bark on the effectiveness of two methods of application (paint and drench) was also compared. Paint alone had no effect on growth and development. None of the plants given treatments with paint with or without PGR, showed any sign of phytotoxicity. Plants exposed to PGRs appeared greener and were shorter than control plants. Both the regular flat latex and SpinOut paints were effective carriers of PGRs, although plants grown in containers coated with PGR/SpinOut paint were taller than plants grown with latex/PGR-coated containers. Composted pine bark slightly reduced the effectiveness of ancymidol on plant growth. This reduction in effectiveness was smaller when ancymidol was carried by latex paint but was greater when carried by SpinOut paint. These results indicate that the paint/PGR method may not represent any real advantage over the drench method to overcome the effect of composted pine bark in the growing mixes on the effectiveness of ancymidol. Chemical names used: β-((4-chlorophenyl)methyl)--(1,1-dimethyl)-1H-1,2,4,-triazole-1-ethanol (paclobutrazol); (E)-(+)-(S)-1-(4chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pent-1-ene-3ol (uniconazole-P); -cyclopropyl-(p-methoxyphenyl)-5 pyrimidinemethanol (ancymidol).