The first major breakthrough in the commercial
feasibility of TGRs on a large scale was the
formulation in the late 1970s of the cell elongation
inhibitors, paclobutrazol, uniconazole, and
flurprimidol for trunk injection. Due to their low water
solubility, it was considered necessary to dissolve
the new generation of growth retardants in either
methyl or isopropyl alcohol. The active ingredients
of these formulations were unquestionably effective
in reducing tree growth