EXPERIMENTS ON SUCROSE FORMATION BY POTATO TUBERS AS INFLUENCED BY TEMPERATURE

Abstract

Analysis of potato tubers during storage at low and high temps, shows that changes take place in the composition of the tubers, not only with regard to starch (which decreases in low temps.), hexoses and sucrose (which increase at low temps.), but also with regard to hexose phosphates. The balance between glucose-6 and fructose-6-phosphate, in particular is greatly affected, the latter being favored at the lower storage temps. Potatoes contain only low amylase activity and this enzyme is essentially inactive in vitro at 0[degree]. This enzyme appears not to be a factor in starch degradation and sugar formation at low temps. Phosphorylase is equally active in potatoes from all storage temps. At no temp, was equilibrium between Cori ester and starch attained in vivo. The fact that phosphorylase does not attack starch in potatoes stored at high temps, seems to have its explanation in the fact that an inhibitor of phosphorylase is formed at high storage temps., but disappears at low storage temps. Hexose interconverting enzymes are more active at low temps. and in tubers stored at low temps. than at high temps. This observation is correlated with the fact that tubers stored at low temps, are high in fructose and fructose-6-phosphate whereas those stored at high temps. are high in glucose and glucose-6-phosphate.