PIGMENTS AND COLOR VARIATION IN FLOWERS O F LAGERSTROEMIA-INDICA

1. To understand the mechanism of flower colour variations from red to purple in crape myrtle cultivars, absorption spectra and Hunter's L, a, b values of intact petals were measured. In this study 67 cyanic pl ants were classified into two groups : red group, lambda(max1), 524 si milar to 544 nm; b/a, (-0.183) similar to (+0.165) : purple group, lam bda(max1) 555 similar to 570 nm; b/a, (-0.785)similar to(-0.442). Rela tively strong absorption about 360 nm was recognized in purple flowers , and high negative correlation (r=-0.897**) was obtained between b/a and E(360)/E(VIS max). 2. Three anthocyanins from the red and purple flowers were isolated, analysed chromatographically and spectrally, an d their ratios determined. All 67 plants contained the 3-glucosides of delphinidin, petunidin, and malvidin as the major anthocyanins. The r atios among these anthocyanins varied widely, but had no correlation t o Hue values (b/a), except that in the red group there was a negative correlation between b/a and the relative malvidin 3-glucoside concentr ation, and a positive one between b/a and relative delphinidin 3-gluco side cone. 3. The pH values measured by tightly pressing the petals to a flat electrode varied from 4.2 to 5.1, but there was no correlation between these values and flower colour. 4. Crude aqueous extracts fro m the red and purple flowers were partitioned with ethyl acetate and t he organic fraction was concentrated; the aqueous fraction was dissolv ed in a buffer solution. Visible absorption maxima shifted bathochromi cally when the above two fractions from red and purple flowers were co mbined. 5. Ellagic acid derivatives detected in the purple flowers are assumed to be the main agents for the blueing of the flowers in crape myrtle.