Role of invertase in the accumulation of sugars in cold-stored potatoes

Abstract

Freshly harvested potatoes contain low levels of total invertase and high levels of invertase inhibitor. Total invertase increases sharply when potatoes are placed in cold storage, but the inhibitor is not depleted in all varieties. The absence of basal invertase activity in Norchip tubers indicates that an excess of invertase is not required for reducing sugar formation. Analyses of 37 varieties and seedlings after 3 months cold storage revealed that the reducing sugar content is not proportional to the invertase activity. High sugar contents are associated with low inhibitor levels, but low sugars are not necessarily associated with high inhibitor levels. The results indicate that invertase participates in reducing sugar formation, but other factors are responsible for the regulation of starch-sugar conversion in potatoes during cold storage.