Other pages about wound healing:
- The Process of Wound Healing
- Healing Factors
- Cutting Seed Tubers
- Handling Seed Pieces
- Wounding at Harvest
- Healing in Storage
When the tuber is cut into seed-pieces, a major wound is formed. This huge break in the skin provides a wide-open portal for a host of pathogens to enter and break down potato tissue. The result of this attack would be low emergence, poor stand, weak plants, and reduced yield and quality. To protect itself from these pathogens, tuber upon being cut or bruised undergoes a healing process referred to as "Wound Healing" or "Tuber Suberization." This process involves the formation of new skin (see panel "Process"). How can wound healing be promoted? What will delay it?
Several factors affect wound healing: Tuber cutting is the most severe of all wounds and has the greatest exposure to pathogens. Some varieties heal faster while others form a thicker protective layer. Physiological age of the tuber affects the extent of the healing (see panel "Tuber Aging"); younger tubers heal better. The three most important and controllable factors are temperature, relative humidity and aeration.
Temperature is the most critical and effective way to promote wound healing or to delay it. Figure 1 shows this effect. As temperature increases, the speed that suberin formation and wound healing is completed increases, that is, it takes less time for the cut to heal. So, if the seed-pieces remain at seed tuber storage temperature, it could take as much as nine weeks to heal but if warmed to room temperature, this would take no more than one week if other conditions are right.
Relative humidity is the next key factor to wound healing. Figure 2 summarizes data from the UK demonstrating the interaction of relative humidity and temperature. At 50 F, higher humidity promotes suberin formation and periderm or skin thickening. Healing at 93% RH gives a distinct advantage over 70%. But at 68 F (room temperature), that distinction disappears. Healing at a humidity above 95% becomes inhibitory as cell proliferation may occur in addition to the danger of condensation on the cut surface blocking out gas exchange.
The last major factor is air. The two key components are oxygen and carbon dioxide, too little of the former and too much of the latter delays cell activity. Remember that wound healing is a cell division process and requires metabolism. Figure 3 summarizes this axiom with regard to wound healing. Wound healing is best when the air contains at least 10% oxygen (O2) and preferably there should be less than 1% carbon dioxide (CO2). Therefore, to promote proper, rapid and healthy healing, the air around seed-pieces must be well ventilated.
Wiggington, M.J. 1974. Effects of temperature, oxygen tension and relative humidity on the wound-healing process in the potato tuber. Potato Res 17:200-214.