Effect of Simulated Grasshopper Grazing on CO2 Exchange Rates of Western Wheatgrass Leaves13

Abstract
Single, intact, fully-expanded leaves of western wheatgrass, Agropyron smithii Rydb., were mechanically damaged to simulate grasshopper feeding. When 4 cm long notches (ca. 25% of the leaf area) were removed from the base and tip of the blade, net photosynthetic rate (PN) per unit of remaining tissue was reduced by 31% within 1 h and remained at ca. this level over the next 6 days. Photorespiration (Rp) and dark respiration (RD) were unaffected by this treatment. Similar PN reductions occurred when a single notch was removed from the base of the leaf or when the top ⅓ of the blade was severed. Removal of a single notch from the tip end of the blade had little impact on PN. The immediate reduction in PN following simulated grazing does not appear to be related to a disruption in water supply to the tissue above the damaged area.