Light-induced variation in phenolic levels in foliage of rain-forest plants : II. Potential significance to herbivores.

The allelochemic activity of the polyphenolics isolated from the leaves of four west African rain-forest plants,Acacia pennata, Cynometra leonensis, Diospyros thomasii, andTrema guineensis, was examined by means of protein precipitation experiments to estimate their specific activity as precipitants. Results indicated that light-induced phenol synthesis in the more heavily insolated foliage of a species led to greater protein-precipitating capacity in these leaves. It is considered doubtful that this produced a quantitative difference in protein availability to an herbivore as, on average, even in the most shaded leaves there was sufficient tannin present to precipitate all the foliar protein. However, taking into account the considerable variability inherent in the results obtained and the adaptations herbivores possess to circumvent the antinutritional properties of tannins, it was concluded that shaded foliage was generally likely to present a nutritionally more acceptable food package on a statistical basis but that acceptable leaves could be found from throughout the light continuum encountered in any of the species studied.