| Abstract
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The linking of essential oil composition to growing conditions and to biological activity is necessary to allow for identification of safe, high quality oils. Pelargonium 'Rober's Lemon Rose' when grown in SC, had a dry weight (DW) oil yield of 1 to 1.5%. Its composition was low in geraniol and high in citronellol and sesquiterpenes, precluding its use in perfumes. It was found to be comparable to commercial geranium oils in its inhibition of human pathogenic bacteria. Pelargonium 'Frensham' was found to produce a citral-based essential oil with a DW oil yield of between 0.2 to 0.6%. When exposed to a 14-day treatment of lead at levels of 0, 250, or 750 ppm daily, there was some impact to its photosynthetic apparatus. This plant was not found to hyperaccumulate lead. Lead treatments increased the citral content of the oil, with a trend for lower oil yield, but the impact was not significant. No lead was found in the oil. For both cultivars, the oil composition varied by source of plant material, indicating mislabeling, environmental impacts, or point mutations. Geraniol and Geranium oil Egypt were found to inhibit tumor formation 15 to 38% at doses between 4 and 80 ppm in the Agrobacterium tumor-induction assay, while other geranium oils had no impact. Citronellol was found to substantially increase tumor formation at 20 and 40 ppm. In a broth dilution assay, citral at 2000 ppm was found to be as effective as carbenicillin at the inhibition of Pseudomonas aeruginosa growth (52%), and when used in conjunction with carbenicillin, increased the inhibition to 77%. Citral appeared to inhibit pyocyanin production, but a chloroform extraction found a phenazine pigment, indicating either pyocyanin in its reduced form or one of its precursors or degradation products. Both the spicy and anise chemotypes of Bay oil inhibited mycelial growth of Phytophthora palmivora. Using a modified 24-well agar dilution assay, it was found that both oils at 500 ppm provided 100% inhibition. The anise oil was more effective at 100 ppm, providing 69% inhibition while the spicy oil gave only 26% inhibition.
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