Some Factors Involved in the Blue Color of ‘Heavenly Blue’ Morning Glory Flowers (Studies on the Flower Color of Morning Glory Part II)

Abstract

The pH of the blue petal juice of ‘Heavenly Blue’ morning glory was 6. 88, while the pH of the white parts of the same petal tissues was 5. 88. Rutin, caffeic acid and some metals, which were quantitatively detected in blue petal tissues, did not produce a significant bathochromic shift in the visible λmax of the main petal anthocyanin, dicaffeyl peonidin 3-sophorosido-5-gluco-side. Spectral examinations showed that the high pH of the petal cells was the major factor in the blue pigmentation, and the color stability of the main petal anthocyanin could be attributed to its acyl group, caffeic acid. In contrast with the main petal pigment, its deacylated anthocyanin in McIlvaine's buffer solutions at different pH was easily converted into a colorless pseudobase and besides into other compounds. © 1980, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.