andpersistency (Rademacher, 2000; Stewart et al., 2000). For that rea-son, there is not a precise recommendation of time and rate ofapplication (Reddy et al., 1995). The sensitiveness to PGRs is dif-ferent among species. For example, the growth regulation effect ofmepiquat chloride in wheat (Triticum sativum L.) requires a dose20-fold higher than the dose required in cotton (Gossypium hirsu-tum), and some species can be virtually insensitive to this retardant(Rademacher, 2000).