Translucent Tissue Defects in Solanum tuberosum L

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Abstract
Kennebec (cv) potatoes randomly developed translucent areas in their centrally located pith-parenchymal cells during storage. These defective areas were characterized as having reduced starch concentration and increased levels of free sugars (i.e. sucrose and glucose) and inorganic PO43-. Electron micrographs of potato tubers stored at 10.degree. .+-. 1.degree. C for 8 mo. indicated that the amyloplast membrane was still intact and continuous around starch granules in both normal and prematurely sweetened tissue. The total activities of phosphorylase and sucrose-6-P synthase were elavated 5.4- and 3.8-fold, respectively, in the defective tissue compared to healthy nonsweetened tubers while there were no significant differences in the levels of sucrose synthase, UDPglucose pyrophosphorylase, invertase, or .alpha.-amylase. Total and specific activities of acid phosphatase were only slightly elevated in translucent tissue but their increase was significant (P < 0.05, t test) over that seen in healthy tubers. Premature sweetening in storage may be indirectly triggered by moisture and heat stress experienced during development. Translucency eventually led to physical deterioration of the tissue.