Bluing of Eustoma flowers induced by molybdenum in hydroponics

Abstract

A solution of ammonium molybdate (Mo: 1 mM) was infiltrated into floral disks of several flower plants that contain anthocyanin to study the basis of bluing caused by molybdenum. The floral disk colors of Eustoma grandiflorum (Raf.) Shinn. 'Tokinoakari', 'Lination Red' and Tulipa gesneriana L. 'Purple Flag' became blue when treated with ammonium molybdate. Those of Eustoma grandiflorum 'Exrosa Blue' and Iris hollandica hort. 'Blue Magic' became slightly bluish. Molybdenum had no bluing effect on Tulipa gesneriana 'Ile de France', Rosa spp. 'Carienta' and Dianthus caryophyllus L. 'Cain'. The minimum concentrations of molybdenum for bluing of excised flower tissues were 0.5 mM in 'Lination Red' and 1 mM in 'Purple Flag' or 'Exrosa Blue'. Aluminum had no effect on flower colors at any concentrations. The flowers of five varieties which showed bluing by molybdenum contained the anthocyanidin, delphinidin. Molybdenum did not affect the color of flowers containing pelargonidin or pelargonidin and cyanidin. Strong bathochromic shifts with molybdenum were also observed in extracts containing delphinidin glycoside or delphinidin spots on thin layer chromatograms. Furthermore, the flower color of Eustoma grandiflorum 'Exrosa Blue Flash', which was grown in hydroponics supplied with ammonium molybdate (Mo:1 mM) before anthesis became bluish.