©2004, European Journal of Histochemistry

In Camptotheca acuminata, we studied the cellular sites of accumulation of the alkaloid camptothecin (CPT), in both plants grown in the field and those grown in a greenhouse, subjecting the latter to stress (i.e., draught, nutritional deficit, and pruning). Fresh sections of the leaf, stem, and root were analysed for the presence of CPT by examining the autofluorescence that the CPT molecule emits when exposed to UV radiation. In the plants grown in the field, CPT was observed only rarely. In the greenhouse plants, CPT had accumulated in crystalline form in the vacuole of specialised cells (i.e., segregator idioblasts), which were not morpholog-ically distinguishable from the cells of the surrounding tis-sues. In the organs examined, the segregator idioblasts were localised in parenchymatic and epidermal tissues. CPT crys-tals were also detected in the glandular trichomes on both the stem and leaf