title: Role of aluminum in red-to-blue color changes in Hydrangea macrophylla sepals.
abstract: Red, purple, and blue sepals on selected cultivars of Hydrangea macrophylla were analyzed for their aluminum content. This content was determined to be a function of the sepal color with red sepals possessing 0-10 μg Al/g fresh sepal, purple sepals having 10-40 μg Al/g fresh sepal, and blue sepals containing greater than 40 μg Al/g fresh sepal. Accordingly, the threshold aluminum content needed to change H. macrophylla sepals from red to blue was about 40 μg Al/g fresh sepal. Higher aluminum concentrations were incorporated into the sepals, but this additional aluminum did not affect the intensity or hue of the blue color. These observations agreed with a chemical model proposing that the concentration of the blue Al(3+)-anthocyanin complex reached a maximum when a sufficient excess of aluminum was present. In addition, the visible absorbance spectra of harvested red, purple, and blue sepals were duplicated by Al(3+) and anthocyanin (delphinidin-3-glucoside) mixtures in this model chemical system.
authors.affiliation: Department of Chemistry, Virginia Military Institute, Lexington, VA 24450, USA. HS@vmi.edu
authors.forename: Henry D
authors.initials: HD
authors.lastname: Schreiber
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Jones
authors.forename: Corinne M
authors.initials: CM
authors.lastname: Lariviere
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Mayhew
authors.forename: Judith B
authors.initials: JB
authors.lastname: Cain
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D000872:Anthocyanins / Q000737:chemistry; D003116:Color; D035264:Flowers / Q000737:chemistry*; D005960:Glucosides / Q000737:chemistry; D031966:Hydrangea / Q000033:anatomy & histology* / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D008956:Models, Chemical; D015394:Molecular Structure; D010858:Pigmentation
chemical_list: D000872:Anthocyanins; D005960:Glucosides; D007477:Ions; C494120:delphinidin 3-O-glucopyranoside; D000535:Aluminum