Some Urea Derivatives Positively Affect Adventitious Root Formation: Old Concepts and the State of the Art.

The success of vegetative propagation programmes strongly depends on adventitious rooting, a postembryonic developmental process whereby new roots can be induced from differentiated cells in positions where normally they do not arise. This auxin-dependent organogenesis has been studied at molecular, cellular, and developmental levels, and our knowledge of the process has improved in recent years. However, bioactive compounds that enhance adventitious root formation and possibly reduce undesirable auxinic side effects are still needed to ameliorate this process. From this point of view, our structure-activity relationship studies concerning urea derivatives revealed that some of them, more specifically, the ,'-bis-(2,3-methylenedioxyphenyl)urea (2,3-MDPU), the ,'-bis-(3,4-methylenedioxyphenyl)urea (3,4-MDPU), the 1,3-di(benzo[]oxazol-5-yl)urea (5-BDPU), and the 1,3-di(benzo[]oxazol-6-yl)urea (6-BDPU), constitute a category of adventitious rooting adjuvants. The results of our studies are presented here, in order either to highlight the positive effects of the supplementation of these urea derivatives, or to better understand the nature of their interaction with auxin.