Analysis of metal elements of hydrangea sepals at various growing stages by ICP-AES

Abstract Flower color in hydrangea is well known to vary greatly. The blue color might develop with aluminum ion (Al 3+ ) from soil; the blue pigment in sepals is an Al-complex with delphinidin 3-glucoside and 5-caffeoyl quinic acid. To clarify the correlation between blue color development and Al-tolerance, flower color and metal content of the sepals were examined with reference to the reflection spectrum and ICP-AES. Blue sepals were found to contain more than 100 ppm Al, and red ones was less than 50 ppm. Change of several element contents along the flower growing stage was also observed. In blue sepals Al ions increased with maturation, but, in red counterpart s the same level was maintained. The content of Fe in blue and red sepals showed a similar behavior to that of Al. However, reconstruction experiments suggested that Al may be responsible for the blue color. Al accumulation and blue color development might reflect a detoxification mechanism for Al in tolerant plants.