Potassium affects enzymatic blackening and after-cooking blackening and low levels of potassium can increase the incidence of after-cooking blackening.
Potassium influences the concentration of organic anions such as citric acid or ascorbic acid (i.e. vitamin C within the tuber). These two molecules have an antioxidative function, which decreases the incidence of enzymatic and non-enzymatic discoloration by slowing down the oxidation processes.
This trial from the USA shows the influence of potassium on enzymatic discoloration on two different varieties.
Low magnesium levels can increase susceptibility to enzymatic discoloration. This trial from the USA shows the influence of magnesium on enzymatic discoloration.
Boron reduces the oxidation of phenols that are responsible for enzymatic discoloration. Thus, a good supply of boron reduces the occurrence of enzymatic discoloration in potato tubers.
This trial from Holland shows the influence of boron on enzymatic discoloration in two different years.