Abstract
Proteinase inhibitor-inducing factor (PIIF)-induced accumulation of trypsin inhibitory activity was assayed in leaves of 23 species of plants representing 10 agriculturally important genera. Inhibitory activity was assayed in extracts from attached leaves or from excised leaves supplied through the cut petioles for 30 minutes with extracts containing the wound hormone PIIF, obtained from either tomato leaves or from the leaves of each plant under study. During subsequent incubation in light for 72 hours, PIIF-induced trypsin inhibitory activity accumulated in significant quantities in 10 of the 23 species. Alfalfa accumulated the highest levels of inhibitory activity (340 mug trypsin inhibited/ml leaf juice), followed by tobacco, tomato, potato, strawberry, cucumber, squash, clover, broadbean, and grape. It is suggested that the inhibitors might be classed as allelochemics that are present in certain plants and not others in response to environmental pressures during their evolution.