Foliar Penetration of Succinic Acid‐2,2‐dimethylhydrazide: Mechanism and Rate Limiting Step

Abstract

The foliar penetration of succinic acid‐2,2‐dimethylhydrazide (SADH) into primary leaves of bean (Phaseolus vulgaris L. cv. Blue Lake) was studied using detached leaves and a leaf disc method. SADH penetration was linear with time and directly related to concentration and the fraction of non‐ionized SADH molecules in the treating solution. The addition of a surfactant, polyoxyethylene sorbitan monolaurate, increasing temperature and light enhanced penetration. Surfactant and light enhanced penetration are discussed in relation to increased wetting and area of contact over guard and accessory cells and the greater permeability of the cuticular ledges in open than in closed stomata. Evidence is presented that foliar penetration of SADH takes place by diffusion controlled by the cuticular membrane. Metabolic processes were not rate limiting.