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Richard N. Arteca, Carl D. Schlagnhaufer, and Jeannette M. Arteca

Four concentrations of GA, (0.05, 0.5, 5.0, or 50 mg·liter–1) were applied to the root systems of seven hydroponically grown geranium (Pelargonium × hortorum cv. Empress Irene, Glacier Crimson, Sincerity, Pink Fiat, Sybil Holmes, and Mrs. Parker and P. × domesticum cv. Lavender Grand Slam) cultivars. The relative growth rate of all cultivars tested increased with GA3 treatments. In conjunction with the increase in growth rate, each of the cultivars showed a reduction in the root: shoot ratio and chlorophyll content per unit leaf area with no change in the percent moisture. These Pelargonium cultivars are genetically diverse, showing that GA3 can stimulate growth over a wide range of cultivars. Chemical name used: gibberellic acid (GA3).

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Carl D. Schlagnhaufer, Richard N. Arteca, and Eva J. Pell

Ethylene production is involved in many plant physiological processes including stress responses and is frequently associated with foliar senescence. Ethylene emission is a common plant response to many biotic and abiotic stresses. We have cloned two ACC synthase cDNAs (OIP-1, PAC-1) from the leaves of ozone treated Solanum tuberosum L. plants. Plants treated with ozone produced ethylene within 1 hour following treatment initiation. Levels continued to increase reaching a peak after 2 h. PAC-1 was expressed after 1 hour reaching a maximum by 2 hours and showed a marked decline after 4 h. OIP-1 was first expressed after 2 hours and high levels of expression continued up to 4 hours following treatment initiation. Leaves treated with CuCl2 produced high levels of ethylene within 0.5 hour after treatment initiation. Ethylene levels continued to increase reaching a peak after 2 hours with no change after 4 h. PAC-1 was expressed after 0.5 hour reaching a peak at 1 hour and showed a progressive decline from 2 to 4 h. However, OIP-1 expression was first detected 2 hours following treatment initiation and high levels of expression continued up 4 h. Leaves exposed to Alternaria solani produced increased levels of ethylene 1 day following inoculation reaching a peak after 3 days. PAC-1 was expressed at a low level 1 day after inoculation and expression remained constant for the duration of the experiment, whereas, OIP-1 was not expressed until day 4.

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Richard N. Arteca, Jeannette M. Arteca, Tzann-Wei Wang, and Carl D. Schlagnhaufer

The purpose of this study was to evaluate physiological, biochemical and molecular changes which occur in unrooted Pelargonium ×hortorum cuttings during storage. Pelargonium cuttings of `Sincerity' (good shipper), `Wendy Ann' (moderate shipper), and `Snowmass' (poor shipper) were stored at 25°C and evaluated over a 5-day period. Following removal from storage, cuttings exhibited progressive declines in photosynthesis, respiration, carbohydrate, starch and protein over time which was significant in all three cultivars, however there was little difference among the cultivars. Ethylene levels produced by `Sincerity' and `Wendy Ann' began to increase 3 days following the initiation of storage, whereas `Snowmass' showed an increase after one day reaching a peak at 3 days and was followed by a sharp decline. When unrooted cuttings of `Snowmass' were stored for a 5-day period at temperatures from 4 to 25°C, it was observed that those stored at 4°C had a significantly higher visual rating, chlorophyll content, root and shoot weight than at higher temperatures tested. The decline in quality progressively became greater from 10 to 25°C. Changes in gene expression of two ACC synthases and an ACC oxidase were evaluated in `Snowmass' cuttings which were stored at 4 and 25°C. Correlations between ethylene and ACC levels with gene expression were observed.

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Richard N. Arteca, Jeannette M. Arteca, Tzann-Wei Wang, and Carl D. Schlagnhaufer

The purpose of this study was to evaluate physiological, biochemical, and molecular changes that occur in unrooted Pelargonium ×hortorum cuttings during storage. Pelargonium cuttings of `Sincerity' (good shipper), `Wendy Ann' (moderate shipper) and `Snowmass' (poor shipper) were stored at 25 °C and evaluated over a 5-day period. Following removal from storage, cuttings of all cultivars exhibited steady and significant decline in photosynthesis, respiration, carbohydrate, starch, and protein over time. However, no significant differences were observed among cultivars for all of these parameters. Ethylene levels produced by `Sincerity' and `Wendy Ann' began to increase 3 days following storage; whereas, `Snowmass' showed an increase after 1 day, reaching a peak at 3 days, and then declined. When unrooted cuttings of `Snowmass' were stored for 5 days at temperatures ranging from 4 to 25 °C, it was observed that those stored at 4 °C had a significantly higher visual rating, chlorophyll content, and root and shoot weight than at higher temperatures tested. As temperature increased from 10 to 25 °C, quality of cuttings declined. Changes in gene expression of two ACC synthases and an ACC oxidase were evaluated in `Snowmass' cuttings stored at 4 and 25 °C. Correlations between ethylene and ACC levels with gene expression were observed. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).