Cover illustration: Nectar of Australian passerine bird-pollinated Anigozanthos flowers (top: flower of A. flavidus, Haemodoraceae) is largely hexosedominated and meets the nutrition requirements of its pollinators. As such it exemplifies plant-pollinator relationships: its nutritive qualities attract the birds which pollinate it. Interestingly the glucose-to-fructose ratio of the floral nectar is not 1:1. The unbalanced ratio between the two hexoses suggests that vigorous metabolic conversion occurs en route from the vascular bundles to the nectaries instead of invertase-catalysed hydrolysis of sucrose and direct secretion into the lumen of the nectary. Liquid-state 13C NMR spectroscopy and various magnetic resonance imaging techniques (middle: 1H gradient echo image; bottom: 1H spin echo image overlaid by a 1H13C cross-polarization image) were used to analyse carbohydrate transport and conversion in vascular bundles and to visualize the anatomy of floral nectaries. Adetailed model of the intermediary metabolic processes of nectar formation is presented. (Photograph of A. flavidus: courtesy D Kessler; design: courtesy C Paetz; see Wenzler et al., pp. 3425-3434.)
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