A method for assessing diurnal changes in concentration of sugars and malate in the pericarp of growing tomato fruit

The content of hexose sugars and malate in growing tomato fruit (attached to the parent plant) have been measured by microassay of extracts from small discs cut from the pericarp. The removal of pericarp discs did not significantly affect fruit growth rate and provided sufficient tissue to analyse accurately the contents of hexose and malate. Several discs could be removed from the same fruit during 24 h, allowing an assessment of any diurnal variation in these constituents during changes of temperature, light and growth rate in fruit grown in glasshouse conditions and in artificially lit controlled environments. Data are presented to validate the microassay and sampling methods, and examples of diurnal fluctuations in sugars and malate are presented.