Préliminaires sur la production de nectar chez trois espèces de Vaccinium

Abstract - A study of the Vaccinium flower nectar secretions
In order to determine if the characteristics of the Vaccinium nectars are responsible for the visits of pollinators (bumblebees, honeybees, hoverflies) (table I), the secretions of V myrtillus, V vitis-idaea and V uliginosum have been analysed for quantity, total sugar concentration and relative ratios of sugars. The quantities of extracted nectar differed among dates, flower ages and species (fig 1), as did total sugar concentration (mean: 18.79% for V myrtillus and 16.40% for V uliginosum) (table II). Great differences are shown between species in chromatographic analysis of their relative sugar ratios. V myrtillus nectar showed sucrose dominance (93.33%), V vitis-idaea had a more balanced nectar composition (28.52% sucrose, 53.24% fructose and 18.30% glucose), and V uliginosum nectar was sucrose poor (0.33% sucrose, 62.98% fructose and 35.93% glucose) (table III). An attempt was made to establish relations between these patterns of variation and foraging behaviour of insects. Actually pollinators are quite similar and it is doubtful that nectar characteristics alone determine visits. Further experiments are required.