FLAVANOLS AS DEFENSE BARRIERS OF THE FRUIT SURFACE

Flavanol deposition was examined histochemically in the fruit skin of 24 fruit crops. A basic feature of all fruits tested was an increasing accumulation towards the outermost skin region. Even in those fruit s pecies with a very low synthetic capacity for flavanols, such as blueb erry and strawberry, there was some faint staining in the epidermis an d the subtending subepidermal layer By far the most abundant flavanol deposition was shown by the entire fruits of sloe and a 4 mm deep frui t border zone of service tree and banana. The stainable flavanols were either dispersed in the entire central vacuole or deposited as inclus ions of varying size within the central vacuole. Estimated analyticall y, the total flavanols of two extreme species, namely sour cherry and service tree, differed about 1000 fold. There was likewise a large dif ference in the flavanol pattern when the individual flavanols of two s pecies (service tree and gooseberry) were separated.