Effects of insect damage on photosynthesis, transpiration and SO2 uptake by sycamore.

This study investigated the effects of damage by the typhlocybine leafhopperOssiannilssonola callosa on the physiology of sycamore seedlings. Feeding by 20 adult leafhoppers for four days produced stippling damage of about 10% of total leaf area. Measurements immediately following removal of the leafhoppers showed a 22% decrease in photosynthesis, 25% decrease in daytime rate of water loss and a 34% increase in night-time rate of water loss, probably due to impaired stomatal function. Sixteen days later control of stomatal function was largely regained with rates of photosynthesis similar to the control plants and slightly higher rates of water loss (6.6% day, 18.0% night) attributable to the still-open feeding punctures of the leafhoppers. Daytime SO2 uptake was similar in damaged and control plants but at night the damaged plants showed a 35% increase in uptake. The hypothesis that leafhopper damage is responsible for this increase is supported by a positive relationship between uptake rate and area of leaf stippled. The physiological effects of leafhopper feeding are greater than the visible damage suggests and the effects are particularly serious when the damage is fresh. Increased rate of air pollutant entry to damaged plants is also a problem, again most marked when damage is fresh.