N,N'-DIBUTYLUREA FROM N-BUTYL ISOCYANATE, A DEGRADATION PRODUCT OF BENOMYL .2. EFFECTS ON PLANT-GROWTH AND PHYSIOLOGY

Experiments were conducted to determine the effects of N,N'-dibutylurea (DBU) on plants. DBU is a product of the reaction between water and n-butyl isocyanate, which is in turn an elimination product of methyl 1-(butylcarbamoyl)-2-benzimidazole (the fungicide benomyl). Corn was unaffected by DBU regardless of rate or time of application. DBU did not affect respiration by hydrilla, seed germination, or seedling emergence of cucumber. At a rate of 2.8 kg ha(-1), DBU reduced cucumber root and shoot biomass between 59 and 63%, regardless of time of application. DBU caused dilation of grana and irregularities in the lamellae of cucumber chloroplasts and completely inhibited photosynthesis (measured as decreased oxygen evolution) of hydrilla after 1 h of exposure. DBU also reduced the peak-to-terminal chlorophyll a fluorescence ratio of hydrilla. DBU probably inhibits photosynthesis and consequently plant growth of susceptible plants.