ISHS Acta Horticulturae 487: VI International Symposium on Processing Tomato & Workshop on Irrigation & Fertigation of Processing Tomato
THE ROLE OF INVERTASE IN CARBOHYDRATE METABOLISM OF TOMATO FRUIT |
| Authors: | S.E. Husain, J. Harrison, C.H. Foyer, T. ap Rees, R. Shields |
| Keywords: | Lycopersicon esculentum, L. pimpinellifolium, invertase, hexoses, soluble solids |
| Abstract:
Two tomato species. Lycopersicon esculentum FM 6203 and L. pimpinellifolium LA 722. and PI 126436 showing large differences in fruit acid invertase activity were used to determine the role of invertase in (1) sink strength and (2) the carbohydrate composition of the fruit. Fruit was tagged at the onset of anthesis and harvested randomly from a population of at least 8 plants between 10 and 50 days after anthesis. The age and colour of the fruit was used as a marker for development. Soluble and insoluble invertase activity of fruit harvested at the green, orange and red stages showed broad pH optima. Maximum activities were observed between pH 3.2 and pH 5.0, with a shoulder between pH 5.5 and pH 6.0. There was no peak or shoulder at pH values above pH 6.0. Insoluble invertase activity was less than 5% of the total invertase activity. Glucose and fructose were predominant carbohydrates. Starch decreased with development in all fruit. Ripe fruit from L. pimpinellifolium PI 126436 had the highest sugar contents and invertase activities while L. pimpinellifolium LA 722 the lowest. In all cases, the activity of invertase found was much greater than that needed to hydrolyse the translocated sucrose. We conclude that the two L. pimpinellifolium cultivars differed markedly in their fruit invertase activities and soluble solids contents. Cultivar LA 722 resembled L. esculentum FM 6203 in both invertase activity and fruit carbohydrate metabolism while cultivar PI 126436 had much higher invertase activities and fruit soluble carbohydrates. | |
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