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 and compared with core, disc, and slice wounds. Bright-field, fluorescence, and transmission electron microscopy were used in conjunction with cytochemical analyses. Wound reaction cells bordering a wound site responded to wounding initially with deposition of callose at the primary pit fields followed by intussusception of lignin in the middle lamellae and primary walls and suberization along the inner surfaces of the primary walls. Suberization was initially detected by the presence of a prosuberin lamella in which suberin lamellae subsequently developed. 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 wounds and at 8 h in bruise wounds. Healing was completed with formation of a continuous wound cork cambium beneath the wound site. With lignification and suberization, wounded potato tubers apparently develop specialized barriers against potential pathogens and water loss. The overall healing process proceeds more slowly in bruise wounds than in cut wounds. Moreover, the capacity for wound healing decreases with increasing age of the tuber, or time in storage.