Analysis of the different regulation levels and mechanisms of the nectar composition

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Floral nectar is produced by many angiosperm flowers to promote crossing mediated by pollinator visits. Sugars account for the largest share of the total nectar solutes, but it also contains a variety of amino acids, inorganic ions, and other compounds. The composition and concentration of individual nectars varies between species and, albeit to a lesser extent, within species. These differences can have various reasons. Firstly, the floral nectar is part of the pollination syndrome, and its composition may represent putative adaptations to the pollinator’s preferences. Secondly, systematic or phylogenetic relationships may have an impact. Thirdly, climatic factors or internal physiological processes, including the metabolism in the nectaries, may affect the composition in different plant species.Results of the previous project phase show that the pollinator has a much higher influence on specific compounds of the nectar than taxonomic affiliations or environmental factors. Apparently, the sugar composition is clearly influenced by the pollination type, whereas the amino acid and inorganic ion compositions are more influenced by the taxonomic group and several other factors, respectively. The present project’s first aim is to determine the crucial influencing factors on the amino acid and ion composition and concentration in nectars in more detail. Floral nectar and nectaries of the model family Bromeliaceae will be analyzed and correlations with systematic relationships, environmental conditions, morphological plant characteristics, and nectary physiology will be calculated.Environmental factors can also influence the nectar composition and initial studies showed that drought had the largest effect. The changed composition in turn can have an impact on the plant-pollinator interactions. As droughts may increasingly occur due to climate changes, analyses of their influence on nectar composition are of growing importance. Therefore, the project’s second aim is to improve the understanding of changes in nectar composition during drought periods in different bromeliad species.Nectar is produced and secreted in nectaries, the species-specific different metabolisms of which may also cause differences in nectar composition. Therefore, the project’s third aim is to clarify this influence on the nectar composition. The basis for the current working model for nectar secretion are primarily results from studies on eudicots, and the pathways of the metabolism and secretion of nectar compounds are not yet completely understood. This particularly applies to monocots or species with special pollination types. The extent to which the mechanisms of nectar production are conserved across species is of particular interest and is also being researched here. The nectar composition is influenced by different factors. To gain understanding of the key influencing and regulatory mechanisms of this essential biological process, comprehensive analyses are necessary.