Solhaug, Erik2020-09-082020-09-082019-06https://hdl.handle.net/11299/216111University of Minnesota Ph.D. dissertation. 2019. Major: Plant and Microbial Biology. Advisor: Clay Carter. 1 computer file (PDF); 175 pages +14 supplemental files.Floral nectar is a sugary solution produced by plants to entice pollinator visitation. Nectar contains a complex mixture of sugars and other compounds, such as amino acids. Although the mechanism of nectar production is somewhat well known from genetics studies in Arabidopsis, very little is known about how nectar metabolites are produced from a metabolic and biochemical perspective. We used Cucurbita pepo (squash) to examine how carbon and nitrogen metabolites are synthesized, partitioned, and secreted into nectar. Toward this end, we analyzed patterns of global transcript levels, followed by a more in-depth examination of enzymes and metabolites in nectar and nectaries. Here we show that C. pepo nectar is most likely secreted by an eccrine mechanism (facilitated diffusion of sucrose) similar to Arabidopsis. Next, we show evidence that sugar transported directly from the phloem, without prior storage as starch, is important for C. pepo nectar secretion. Similarly, we demonstrate a role for trehalose-based sugar signaling in regulating nectar production. Finally, we have found that nectaries undergo extreme anoxic conditions during nectar secretion and that nitrate reduction to nitric oxide and alanine metabolism are essential for regenerating NAD+ to maintain ATP synthesis for the energetically demanding process of nectar synthesis. These data improve our understanding of how nectar components are produced in an agronomically-relevant species with the potential for use as a model to help us gain insight into the biochemistry and metabolism of nectar secretion in flowering plants.enCarbonMetabolismNectarNitrogenSquashThesis or Dissertation