© 1991 Heron Publishing—Victoria, Canada
Physiological responses of pear thrips-damaged sugar maples to light and water stress
T. E. Kolb, L. H. McCormick and D. L. Shumway
School of Forest Resources, 12 Ferguson Building, Pennsylvania State University, University Park, PA 16802, USA / Received November 6, 1990
Summary
We assessed the effect of feeding damage by pear thrips, Taeniothrips inconsequens Uzel (Thysanoptera:Thripidae), on gas exchange and water relations of sugar maple (Acer saccharum Marsh.) seedlings. Compared to undamaged seedlings, feeding punctures in the leaf epidermis of thrips-damaged seedlings decreased
water use efficiency, increased leaf conductance to water vapor, and decreased predawn water potential. Under conditions of
high soil water and high light intensity, carbon dioxide exchange rate (CER) was greater for thrips-damaged than undamaged
seedlings because of greater CO2 conductance through feeding punctures. Under conditions of low soil water, CER was lower for thrips-damaged than undamaged
seedlings as a result of water stress. Carbon dioxide exchange rate at low light and low soil water was limited by non-stomatal
factors, but no difference in non-stomatal limitation to CER was detected between thrips-damaged and undamaged seedlings.
Leaf tissue water relations differed between thrips-damaged and undamaged seedlings and under high and low soil water conditions.
The results suggest that the reduction in leaf area of thrips-damaged seedlings can be partially compensated by elevated CER
under conditions of high light intensity and high soil water. However, high gas exchange rates through feeding punctures predisposes
thrips-damaged seedlings to water stress that can reduce CER under conditions of low soil water.
