Floral pigments and their perception by avian pollinators in three Chilean Puya species

Abstract

The Chilean Puya species, Puya coerulea var. violacea and P. chiliensis bear blue and pale-yellow owers, respectively, while P. alpestris considered to be their hybrid-derived species has unique turquoise owers. In this study, the chemical basis underlying the different coloration of the three Puya species was explored. We rst isolated and identi ed three anthocyanins: delphinidin 3,3′,5′-tri-O-glucoside, delphinidin 3,3′-di-O-glucoside and delphinidin 3-O-glucoside; seven avonols: quercetin 3-O-rutinoside 3′-O-glucoside, quercetin 3,3′-di-O-glucoside, quercetin 3-O-rutinoside, isorhamnetin 3-O-rutinoside, myricetin 3,3′,5′-tri-Oglucoside, myricetin 3,3′-di-O-glucoside and laricitrin 3,5′-di-O-glucoside; and six avones: luteolin 4′-Oglucoside, apigenin 4′-O-glucoside, tricetin 4′-O-glucoside, tricetin 3′,5′-di-O-glucoside, tricetin 3′-Oglucoside and selagin 5′-O-glucoside from their petals. We also compared compositions of oral avonoid and their aglycone among these species, which suggested that the turquoise species P. alpestris has an essentially intermediate composition between the blue and pale-yellow species. The vacuolar pH was relatively higher in the turquoise (pH 6.2) and pale-yellow (pH 6.2) ower species, while that of blue ower species was usual (pH 5.2). The ower color was reconstructed in vitro using isolated anthocyanin, avonol and avone at neutral and acidic pH, and its color was analyzed by re ectance spectra and the visual modeling of their avian pollinators. The modeling demonstrated that the higher pH of the turquoise and pale-yellow species enhances the chromatic contrast and spectral purity. The precise regulation of ower color by avonoid composition and vacuolar pH may be adapted to the visual perception of their avian pollinator vision.