WOUND-HEALING IN WHOLE POTATO-TUBERS - A CYTOCHEMICAL, FLUORESCENCE, AND ULTRASTRUCTURAL ANALYSIS OF CUT AND BRUISE WOUNDS

Healing was investigated in whole tubers wounded by cuts and bruises a nd compared with core, disc, and slice wounds. Bright-field, fluoresce nce, and transmission electron microscopy were used in conjunction wit h cytochemical analyses. Wound reaction cells bordering a wound site r esponded to wounding initially with deposition of callose at the prima ry pit fields followed by intussusception of lignin in the middle lame llae and primary walls and suberization along the inner surfaces of th e primary walls. Suberization was initially detected by the presence o f a prosuberin lamella in which suberin lamellae subsequently develope d. Both lignin and the prosuberin lamella were first detected in wound reaction cells of the cortex at 4 h in cut, core, disc, and slice wou nds and at 8 h in bruise wounds. Healing was completed with formation of a continuous wound cork cambium beneath the wound site. With lignif ication and suberization, wounded potato tubers apparently develop spe cialized barriers against potential pathogens and water loss. The over all healing process proceeds more slowly in bruise wounds than in cut wounds. Moreover, the capacity for wound healing decreases with increa sing age of the tuber, or time in storage.