Bluing of Eustoma Flowers Induced by Molybdenum in Hydroponics

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' anc 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 'He 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' 01 'Exrosa Blue'. Aluminum had no effect on flower colors at any concentrations. The flowers ol five varieties which showed bluing by molybdenum contained the anthocyanidin, delphinidin Molybdenum did not affect the color of flowers containing pelargonidin or pelargonidin anc cyanidin. Strong bathochromic shifts with molybdenum were also observed in extracts containing delphinidin glycoside or delphinidin spots on thin layer chromatograms. Furthermore, the flowei color of Eustoma grandiflorum 'Exrosa Blue Flash', which was grown in hydroponics suppliec with ammonium molybdate (Mo:l mM) before anthesis became bluish.