Elsevier

Scientia Horticulturae

Volume 24, Issues 3–4, December 1984, Pages 349-358
Scientia Horticulturae

Comparison of a new triazole retardant paclobutrazol (PP 333) with ancymidol, chlorphonium chloride, daminozide and piproctanyl bromide, on stem extension and inflorescence development in Chrysanthemum morifolium Ramat

https://doi.org/10.1016/0304-4238(84)90120-1Get rights and content

Abstract

Several experiments in glasshouses at different times of the year have demonstrated that a new growth retardant, paclobutrazol (PP 333), applied as a single compost drench or as a foliar spray, is very effective in controlling stem extension in the pot chrysanthemum (Chrysanthemum morifolium) ‘Bright Golden Anne’, a tall cultivar. Moreover, the concentration required, 30–50 mg a.i. l−1, was much lower than with a drench of chlorphonium chloride (Phosfon/Phosfleur), or with a foliar spray of daminozide (Alar/B-Nine) or piproctanyl bromide (Alden/Stemtrol).

In two trials, a comparison of paclobutrazol and ancymidol (A-Rest/Reducymol) drenches indicated that, on a weight basis, the two compounds induced approximately equal dwarfing, whereas foliar sprays of paclobutrazol were more active than those of ancymidol, particularly at the lower concentrations. As before, at least 50–100 times the concentration of daminozide was needed than of paclobutrazol or ancymidol in order to induce an equivalent response. However, the variability in lateral stem length within a pot of 12 flowering shoots was a little higher with foliar sprays of paclobutrazol than with daminozide, possibly indicating that the amount of paclobutrazol transported to its site(s) of action varied more between shoots.

Paclobutrazol produced similar delays in flowering (which invariably accompany commercially adequate reductions in plant height) to ancymidol and daminozide, whereas the delays with chlorphonium chloride and piproctanyl bromide were 2–4 days greater. In an experiment with the dark pink ‘Regal Anne’, daminozide caused some loss of flower pigmentation, but paclobutrazol and the other compounds did not.

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