Mainly because of the fear that the new chemicals would injure and lower the quality of turf, in situations where turf quality is of utmost importance. PGRs have a long history of being used on areas that are dangerous or difficult to mow. This has enabled PGRs to be used on high quality turf areas such as fairways, tees and even greens. Primo from Ciba-Geigy Corporation. Trinexapac-ethyl retards the growth of the grass plant by slowing cell elongation rather than altering the growth.
Growth promoters are usually plant hormones.
There are two major actions of plant growth regulators. They can either increase plant growth or retard the growth which actually decreases the amount of overall vegetative material produced. The metabolism of cytokinin is slowed mainly by Type I PGRs. When using Type I PGRs seedhead reduction is usually the preferred effect. Type II PGRs inhibit cell elongation.