Oxidative Enzymes, Ribonuclease, and Amylase in Lemon Buds Infested with Aceria sheldoni (Ewing) (Acarina: Eriophyidae)

Abstract

In lemon buds the optimum for peroxidase activity was a reaction mixture of 0.03 M guiacol, 0.1 per cent enzyme (acetone powder), and 0.0086 per cent H²O², in 0.015 M acetate buffer pH 4.0. For polyphenoloxidase activity the optimum was a reaction mixture of 0.3 per cent catechol and 0.025 per cent enzyme (acetone powder), in 0.05 M phosphate buffer pH 7.0. Both enzymes were strongly affected by mite infestation. The activity of polyphenoloxidase and peroxidase in infested buds reaches respectively two and three times that in uninfested buds. There are indications that the enhanced oxidative activity and corresponding increase in phenol level in the infested buds is part of a defence system which may develop in the plant after infestation. The optimum for RNAase activity was a reaction mixture of 0.06 per cent RNA and 0.02 per cent purified enzyme, in 0.035 M sodium potassium-buffer pH 5.6. An increase of about 30 per cent in RNAase activity occurred after mite infestation. Amylase activity was affected slightly only after a heavy infestation.