What Makes a Leaf Tough and How This Affects the Pattern of Castanopsis fissa Leaf Consumption by Caterpillars

The toughness of the midrib, secondary veins and lamina of mature leaves of Castanopsis fissa corresponded to the consumption pattern of caterpillars. Midrib and secondary veins were the toughest tissues and were consumed significantly less than the lamina, which was least tough. 2. Tertiary and higher order veins embedded in the lamina contributed most to lamina toughness but were less tough than secondary veins. Lamina toughness could be predicted by the cell-wall volume fraction of component tissues and by neutral detergent fibre content, confirming that these made leaves tough. 3. Young leaves had higher total soluble phenolics content. Mature leaves had lower phenolics but higher toughness. They were eaten less than young leaves which supports the hypothesis that toughness is the major deterrent to these herbivores.