Acids in Storage Tissues. Effects of Salts and Aging

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Abstract
The effects of salt composition and concentration of the medium on levels of malate and succinate in discs of red beet tissue, and the relationship between ion absorption and acid accumulation were investigated. Aeration in water induced a roughly 8-fold increase in malate and succinate levels. Progressively larger amounts of acid accumulated as the concentration of potassium phosphate (pH 7.4) was increased, and at 0.1 [image], an 80-fold increase over the initial level of malate occurred. Sodium and ammonium phosphate produced similar effects. Low RQ values were observed during malate accumulation and the results were shown to be consistent with refixation of respired CO2 to produce malate in amounts roughly equivalent to the excess cation absorption. Changes in acid levels and O2-uptake during aging were measured in red beet, carrot, and potato discs. As shown previously by others, the respiration of potato discs aged in CaSO4, KHCO3 solutions was not inhibited by 0.05[imager]M malonate, in contrast to that of slices aged under a variety of other conditions. However, this resistance to malonate was not a qualitative property; increased malonate concentrations produced the anticipated inhibition. Discs aged in CaSO4, KHCO3 solutions were found to accumulate larger amounts of succinate and malate than discs aged in other solutions.