AN ULTRASTRUCTURAL-STUDY OF BRUISING IN STORED POTATO (SOLANUM-TUBEROSUM L.) TUBERS

Potato tubers of the cultivar Pentland Dell were investigated for ultr astructural changes following impact. Studies were carried out on tube rs after 12 and 24 wk of storage using a falling bolt delivering 0.7 J of energy. Ultra-thin sections were examined by light and transmissio n electron microscopy. Tubers stored for 12 wk exhibited no visual bru ise formation, whereas visible bruising resulted following impact of t ubers stored for 24 wk. An ultrastructural sequence of events during b ruising was established as (1) a collapse of intracellular compartment ation, (2) increased ribosomal and mitochondrial abundance within the cytoplasm, (3) increased density of cytoplasm adjacent to the cell wal l and surrounding amyloplasts, and (4) the development of melanin in b ruised cells. These observations are discussed in relation to tuber tu rgor and physiology during storage.