Abstract
Plant growth-regulating factor and oxidative enzyme activities in the injured and surrounding tissues of sugar beet leaf attacked by Lygus disponsi were assayed. Phenoloxidase activities increased and substances reacting with SALKOVSKI reagent decreased in the vein tissue injured by L. disponsi and the surrounding mesophyll tissues. A plant growth-regulating factor was not detected in either the injured or the uninjured tissue, whereas a plant growthinhibiting factor was found both in the surrounding mesophyll and in control tissues. Its effect did not differ between the former and the latter. The significance of substances reacting with SALKOVSKI reagent and of the nicrease of phenoloxidase activies in the mesophyll tissues surronding the injured vent tissue is discussed in relation to the occurrence of the leaf malformation in the sugar beet plant.
