ANATOMY AND COMPOSITIONAL VARIATION WITHIN POTATOES .2. PHENOLICS, ENZYMES AND OTHER MINOR COMPONENTS

Minor components, including principal phenolics and certain enzymes, are distributed within the potato tuber according to patterns that are significant to many practical problems in the growing, handling, and utilization of potatoes. Chlorogenic acid is much more concentrated in outer than in inner tissue zones; is also highly concentrated in the phloem and phloem parenchyma tissues of both cortex and perimedullary zone. Tyrosine is generally distributed but is more concentrated in the stem end than in the bud end of the tuber and probably is also more concentrated in central than in outer tissues. Results of histochemical tests on distribution of these phenolics agree in general with quantitative analytical results. Phenolases and peroxidase also show characteristic patterns of distribution. Peroxidase affects tissue differentiation and specialization and shows strong histochemical relationship with cell-wall specializations. Phenolases show association with distributions of phenolic substrates and usually are associated with cell contents. Distribution patterns are reviewed for other minor constituents, such as, iron, copper, ascorbic acid, thiamine and solanin. © 1969 Springer.