Responses of Sycamore (Acer Pseudoplatanus) Leaves to Damage by a Typhlocybine Leaf Hopper, Ossiannilssonola Callosa

Abstract

A typhlocybine, O. callosa, had a mean density of only 0.02 adults per leaf on sycamore (A. pseudoplatanus) in a part of a woodland which was foraged by the ant Formica rufa, but 0.44 adults per leaf in the ant-free parts of the wood. Feeding damage caused by O. callosa caged on leaves in the ant-foraged woodland was compared with healthy parts of the leaf lamina which had been kept free of O. callosa and other herbivores by ants. Each adult O. callosa removed the contents of mesophyll cells causing stippling of 4 cm2 of leaf in 10 days by inserting its mouthparts through the abaxial epidermis. Scanning electron microscopy of the abaxial leaf surface showed feeding punctures caused by O. callosa to occur with about the same density and of the same order of size as the stomata. The punctures remained open for at least 3-4 wk after they were made. Water vapor conductance from the stippled areas of the leaf was 18% greater than from undamaged areas during daytime and 75% greater at night. Net photosynthesis was almost 3 times greater on the undamaged part of the lamina compared with the stippled areas and there was evidence of damage to the photosynthetic mechanism. The nature of the feeding damage and its effect on leaf physiology are discussed.