Browsing by Subject "nectar"
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Item Effects of Gibberellins on Nectar Production in Arabidopsis thaliana(2015-12) Wiesen, LisaGibberellins (GA) are well known for their roles in regulating stem elongation and seed germination, but less understood is the role of GA in regulating floral maturation. We recently identified GA 2-OXIDASE 6 (GA2OX6, At1g02400) as being highly expressed in the actively secreting nectaries of Arabidopsis thaliana, but at low levels in other tissues. GA2OX6 was previously demonstrated to inactivate bioactive GA. Multiple independent ga2ox6 mutants displayed decreased nectar production, which suggests that elevated levels of active GA negatively regulate nectar production. Similarly, spindly (spy) mutants, which also have an increased GA signaling response, displayed decreased nectar production, further supporting the hypothesis that GA negatively regulates nectar production. Wild-type flowers also displayed an intense auxin response in actively secreting nectaries, whereas ga2ox6 and spy mutants had strongly reduced DR5-dependent signal in nectaries. This suggests significant crosstalk occurs between GA and auxin signaling pathways in the regulation of nectar production.Item Insights into the hormonal regulation of nectar production and the biochemical characteristics of antimicrobial nectar proteins(2021-12) Schmitt, AnthonyNectar is a complex, carbohydrate rich solution that facilitates important plant-biotic relationships. Of the utmost importance is nectars ability to effectively attract and manipulate pollinators to maximize plant reproductive success while deterring unwanted consumers that could be deleterious to a plant’s fecundity. Therefore, the regulation of nectar secretion during times of peak pollinator activity, as well as other essential plant reproductive processes, is essential. Very little is known about the detailed mechanisms of nectar regulation and whether these mechanisms are conserved in the plant kingdom. Through the examination of null alleles of JA biosynthesis and response genes in Arabidopsis, this report finds that the octadecanoid pathway plays an important role in nectar production. The nectar-less JA synthesis mutant aos-2 showed no auxin response in nectaries, but both nectar production and the auxin response were restored upon exogenous JA and auxin treatment. Cumulatively, these observations strongly suggest an indispensable role for an octadecanoic acid- and auxin-dependent, but JA- and COI1-dispensible, pathway in regulating nectar production in Arabidopsis. Another important aspect of nectar biology is the chemical constituents of nectar droplets. While sugars are the predominant solutes of nectar, non-sugar solutes have been shown to provide additional levels of functionality to nectar. Some of these non-sugar solutes include amino acids, lipids, ions, secondary metabolites and proteins. Nectars generally secrete small arrays of proteins. Because nectar is a nutrient dense solution, it must be protected against non-mutualistic consumers such as deleterious communities of microorganisms. Nectar proteins generally exhibit direct and indirect antimicrobial activity and are thought to serve as a defense mechanism for nectar. To this end, I characterized non-specific lipid transfer proteins (nsLTPs) that are secreted into the nectar of Arabidopsis (AZI7), Cucurbita pepo (CpLTP1.1), and Brassica rapa (BrLTP2.1). Broadly, these nectar specific nsLTPs appear to have strong antimicrobial activity, particularly against pathogenic plant fungi, are very heat stable, and have some capacity to bind free fatty acids. Overall, these data improve our understanding of the hormonal regulation of nectar and takes the initial steps to gaining broad insight to the biological function of nectar proteins.Item Post-Fire Associations Of Butterfly Behavior, Occupancy, And Abundance With Environmental Variables And Nectar Sources In The Sierra Nevada, California(2015-12) Pavlik, DavidFire can alter the quality of habitat for butterflies. Fire also affects environmental attributes associated with the distribution, abundance, and reproduction of butterflies. The effects of fire on butterfly occupancy, and on environmental attributes that are associated with butterfly occupancy, are largely unknown. In 2014 and 2015, we conducted butterfly and vegetation surveys within the Rim Fire boundary in California. We analyzed sugar and sucrose masses, and proportion of sucrose, in 20 nectar sources. We found no evidence that intensity of use was associated with sugar mass, mass of sucrose, or the relative proportion of sucrose. We found that environmental attributes associated with occupancy of some species were also associated with the abundances of those species. Burn severity affected environmental attributes that were associated with butterfly occupancy and abundance. Understanding how fire affects environmental attributes associated with occupancy and abundance can inform use of prescribed fire or management following wildfire.