LOCALISATION OF STARCH GRANULES IN DEVELOPING TOMATO FRUIT

Starch is accumulated in developing tomato fruit to levels approaching 20% dry weight at or around 20 days post anthesis. Subsequently levels fall steadily until very little remains in mature fruit. However total levels may mask localised differences between tissues in their handling of starch and other metabolites.

To investigate this possibility several varieties of the commercial processing tomato (Lycopersicon esculentum) were grown under controlled conditions and samples taken for microscopic analysis. A number of techniques were then used to visualise starch including tissue imprinting and wax-imbedding. At early stages, during maximum cell division starch is found predominantely in the placenta with a small amount in the inner pericarp. As the fruit matures and enters the cell expansion stage the numbers of discrete starch granules drop - those remaining are found more and more in the placental region. However in the mature fruit there is almost a complete abscence of granules in the red fruit.

The implications of these results for the different sensitivities of the different cells within the fruit is discussed.