Antioxidant enzyme activities during tomato fruit ripening and in response to phosphorus nutrients
T. Ahn, A. Schofield and G. Paliyath
Proceedings of 26th International Horticultural Congress. Volume of Abstract . Toronto, Canada, 11-17 August, 2002. Abstract S09-O-182. pp. 266.
2002
บทคัดย่อ
Changes in activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POX) and ascorbate perosidase (APX) were determined in cherry tomatoes and processing tomatoes during fruit development. In cherry tomatoes, activities of SOD and POX were the highest at the orange stage, and were the lowest at the red stage, and were nearly similar at the initial stages of dvelopment. By contrast, APX activit was the lowest at the mature green stage. Native PAGE and enzyme activity staining of the gels showed three isozymes of SOD. The staining intensities of the two slowmigrating isozymes were nearly the same at all developmental stages. The third fast-migrating isozyme was present at the young, intermediate and mature green stages, but declined considerably at the orange and red stages. Peroxidase activity was localized in two isozymes, a major fast-migrating isozyme and a minor slow- migrating isozyme. The staining intensity of both these isozymes at all stages was nearly the same. APX was characterized by two isozymes, a minor, fast-migrating isozyme and a highly intense, slow-migrating isozyme. The staining intensity of the slow-migrating isozyme increased condiderably at the orange and red stages, in parallel with the activity estimatiions. A nearly similar profile of antioxidant enzymes was detected in processing tomatoes. In general, soil and foliar phosphorus fertilization enhanced the antioxidant enzymes as revealed by their in vitro activity and activity staining. The maintenance of these enzyme activities during the ripening stages may potentially help in the detoxification of actives oxygen species that are generated during catabolic activities and maintain the quality of fruit longer.