Further studies will be necessary to understand the factors thatinfluence the effect of Pix®and Stance®on castor plants at fieldconditions. Some hypothesis are that: (i) the thick leaf cuticle ofcastor leaf reduces the absorption of the PGR, (ii) the PGR is washed(by rain) or dries in the leaf surface before it is absorbed intothe leaf, and (iii) the PGR prevents growth for a short period, butthe growth is compensated later when environmental conditionsremain favorable.