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'-dibutylure a (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 u naffected by DBU regardless of rate or time of application. DBU did no t affect respiration by hydrilla, seed germination, or seedling emerge nce 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 applicati on. DBU caused dilation of grana and irregularities in the lamellae of cucumber chloroplasts and completely inhibited photosynthesis (measur ed as decreased oxygen evolution) of hydrilla after 1 h of exposure. D BU also reduced the peak-to-terminal chlorophyll a fluorescence ratio of hydrilla. DBU probably inhibits photosynthesis and consequently pla nt growth of susceptible plants.