Abstract
Some biological changes were observed in the tissue of the sugar beet leaf injured by Lygus disponsi LINNAVUORI. The dry weight percentage of the injured tissue increased just after the infestation period (3 to 4 days), but then decreased gradually as days elapsed. Polyphenoloxidase and peroxidase activities increased rapidly from the 1st to the 3rd-4th day after the injury and kept high levels till the 18th day. The amount of phenol compounds and phosphatase activity changed with the lapse of days in a way similar to the oxidative enzyme activities. The physiology of the injury caused by L. disponsi was discussed with regard to sugar beet plant.
