Enzyme activity in bioregulator-treated tomato (Solanum lycopersicon) genotypes.

Abstract

The challenges of using exogenous plant bioregulators to manipulate plant responses by researchers and producers are increasing rapidly. In previous studies, we have demonstrated that 100 mg/l concentration of the bioregulators; indole-acetic acid (IAA), indole butyric acid (IBA) and naphthalene acetic acid (NAA) is suitable for tomato growth in the field. In this work, spectrophotometric analysis was conducted to determine the level of enzymes that could affect the keeping quality of the fruits harvested at the orange-red ripe stage following pre-sowing seed treatments with 100 mg/l solutions of the bioregulators. The NHLy 11, NHLy 12, NHLy 13, NHLy 15 and NHLy 16 genotypes were used and the activities of lipoxygenase (LOX), catalase, peroxidase, alcohol dehydrogenase and acid phosphatase determined. All treated genotypes showed high LOX activity with a range of 0.06 - 1.07 mmol.abs.units (A234). The NAA-treated NHLy13 genotype had complete loss of catalase activity after 210 s. Peroxidase activity was higher in NAA-treated genotypes with values between 0.07 and 0.62 abs. units/g (A430) while alcohol dehydrogenase activity suffered a decline in all IBA-treated genotypes. IAA gave consistently higher acid phosphatase activity than IBA and NAA in all the test genotypes. These findings have important implications on the biochemical changes associated with the fruits during storage and processing.