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David S. Koranski and Chad G. Ingels

Petunia seeds of `White Cascade', `Red Flash', and `Red Madness' were sown in 406 plug trays on the same date. The first transplanting occurred when the plants could be removed from the cells without root damage. Subsequent transplanting occurred for four weeks. The first transplanting of `White Cascade' flowered two weeks earlier than the second while the third transplanting was one week behind the second. `Red Flash' flowered two weeks earlier for the first transplanting. There was no effect on time to flower for the `Red Madness'. The highest fresh and dry weights corresponded to the earliest flowering transplants. Optimum growth and development for most petunia cultivars was obtained with the earliest transplanting without root damage.

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David S. Koranski and Chad G. Ingels

Tempered water of 50, 60, 70, and 80 degrees F was applied to petunia `Royal Cascade', Impatiens `S.E. Pink', Vinca `Little Bright Eye', and Pansy `Majestic Giant Mix' during seed germination in the plug and in the pack. There was no effect on germination for any of the crops. The height of plug seedlings of petunia and pansy was inhibited by 50 degree F by as much as 20 percent. There was significant effects on plant size in the cell packs. A water temperature of 70 degrees F resulted in the largest plants in all crops. Height of petunia, impatiens, vinca, and pansy was reduced 20, 30, 32, and 49 percent at 60, 50, and 80 degrees F, respectively. Tempered water at 70 degrees F was ineffective in controlling plant height while water temperatures of 50 and 60 degrees F provided the best control of plant compactness. Fresh root weight for all plants was greatest at 70 degree F water. Fresh root weight was reduced 29% in petunias, 34% in impatiens, and 48% in pansy, all at 60 degrees F. Vinca fresh root weight was reduced 33% at 50 degrees F.

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Abdulrhman I. Al-hemaid and David S. Koranski

Petunia `Red Flash', Vinca `Little Blanch', Pansy `Magestic Giant Purple', and Impatien `Super Elfin Red' plugs were held in the greenhouse after they reached the saleable size in 200, 406, 512, and 800 for 1 to 3 weeks Pansy plugs were held in coolers at 40, 50, or 60F under fluorescent light for 16 hrs photoperiod for 1 to 3 weeks in 200, 406, 512, or 800 plug trays. All plants ware transplanted weekly and were grown in the greenhouse until flowering and data were collected. For plants bald in the greenhouse, plants were affected by transplanting time. As the holding time increased the final height, diameter, flower number, and fresh and dry weight of plants decreased. The flowering time was delayed by increase the holding time, regardless of plant variety, As cell size decreased, plant height, diameter, flower number, and fresh and dry weight decreased. For plants held in the coolers, the flowering time was delayed by the transplant time, regardless of cooler temperatures Plant quality was not affected by the treatment. The height, diameter, flowers number, and fresh and dry weight of plants showed a little effects by temperatures, cell size, and transplanting time.

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Abdulrhman I. Al-hemaid and David S. Koranski

Petunia `Red Flash', Vinca `Little Blanch', Pansy `Magestic Giant Purple', and Impatien `Super Elfin Red' plugs were held in the greenhouse after they reached the saleable size in 200, 406, 512, and 800 for 1 to 3 weeks Pansy plugs were held in coolers at 40, 50, or 60F under fluorescent light for 16 hrs photoperiod for 1 to 3 weeks in 200, 406, 512, or 800 plug trays. All plants ware transplanted weekly and were grown in the greenhouse until flowering and data were collected. For plants bald in the greenhouse, plants were affected by transplanting time. As the holding time increased the final height, diameter, flower number, and fresh and dry weight of plants decreased. The flowering time was delayed by increase the holding time, regardless of plant variety, As cell size decreased, plant height, diameter, flower number, and fresh and dry weight decreased. For plants held in the coolers, the flowering time was delayed by the transplant time, regardless of cooler temperatures Plant quality was not affected by the treatment. The height, diameter, flowers number, and fresh and dry weight of plants showed a little effects by temperatures, cell size, and transplanting time.

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Paul T. Karlovich and David S. Koranski

Fifteen lots of impatiens representing five cultivars were used to evaluate the potential of a soak test for predicting the performance of impatiens seeds in plug-production systems. This test would be valuable in breeding programs because it is non-destructive, seed-specific, inexpensive, fast, and does not require large numbers of seed. The soak test submerged individual seeds in one ml distilled water during germination. The results of this test were compared to standard blotter germination and to plug tray performance in the Iowa State University greenhouse and at two commercial greenhouses. Different responses to the soak test were found among lots and cultivars but the differences could not be correlated to the plug tray performance of the seeds. The responses to the soak test do not appear to be genetically related for these cultivars.

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Mehrassa Khademi, David S. Koranski, and Joan Peterson

Seeds of Primula acaulis (L.) J. Hill `Dukaat Helderrose' were imbibed for 48 h at 18C, and Maltrin 600 solution was used to separate them into density classes of 1.10, 1.12, 1.14, 1.16, and 1.18 g·cm-3. Seeds were rinsed, air-dried for 48 h at 22C, and germinated at 18C; 80% were separated into density classes between 1.16 and 1.18 g·cm-3. Percentages of germination and high-vigor seedlings were significantly greater for seeds with densities >1.14 g·cm-3. Soluble protein concentration increased with density, whereas insoluble protein concentration was unchanged. Distinct protein groups with estimated molecular weights of ≈50, 33, and 25 kDa were present in the protein profile of nonseparated imbibed seed. These proteins were most abundant at densities ≥1.16 g·cm-3. The 25-kDa protein was present only in higher density seed. Presence of an additional 14-kDa protein was noted in the insoluble protein profile. Certain proteins in the soluble protein fraction maybe used to test for seed vigor.

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Raymond Kessler, Allan M. Armitage, and David S. Koranski

Plug flats of Begonia × semperflorens-cultorum Hort. `Pizzazz Red', Vodka', and `Viva' were provided 0, 50, 125, or 200 μmol·s-1·m-2 metal-halide supplemental irradiance in the greenhouse for 0, 2, 4, 6, or 8 weeks. Treatments were initiated when seedlings were in the first true leaf stage (2 weeks after sowing). Plug-grown begonias reached transplantable dry weight and leaf area after 4 weeks of 125 μmol·s-1·m-2 supplemental exposure, while those under O and 50 μmol·s-1·m-2 required 6 to 8 weeks. Fewest number of days to visible bud and anthesis and the fewest number of nodes for all cultivars occurred after 2 weeks of 125 μmol·s-1·m-2 supplemental exposure. The same conditions achieved the greatest final leaf area and plant height; however, final dry weight was unaffected. Additional supplemental irradiance and/or exposure time did not accelerate flowering or improve vegetative growth of finished plants.

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Gary F. Polking, Richard J. Gladon, and David S. Koranski

Generation of pregerminated seeds at a central facility and subsequent mechanical sowing at a remote facility require that radicle elongation during shipment be minimized. Low-oxygen treatments were applied to pregerminated `Super Elfin Salmon Blush' impatiens seeds to suppress radicle growth during a subsequent one-day simulated shipping period in air. In the first experiment, O2 concentrations of 0, 3, 7, 10, 13, and 20% were applied for 24 and 48hr. The 0% O2/24-hr and the 0% O2/48-hr treatments held the radicle length close to the desired length of 1.0mm, but both of these treatments decreasad 7-day hypocotyl length and percentage normal seedlings, when they were compared with the control treatment (untreated pregerminated seeds) In the second experiment, O2 concentrations of 0, 1, 2, 3, 7, and 20% were applied for 24 and 48hr. Five treatments (0, 1, and 2% O2/24-hr and 0 and 1% O2/48-hr) held the radicle to a length <1.0mm. Of these five treatments, only the 2% O2/24-hr treatment resulted in recovery parameters (7-day hypocotyl length and percentage normal seedlings) that compared with those of the control treatment.

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Gary F. Polking, Richard J. Gladon, and David S. Koranski

Germinated Impatiens wallerana Hook. f. `Super Elfin Salmon Blush' seeds were exposed to subatmospheric O2 concentrations for 12, 24, or 48 hours at 25C. Suppression of radicle growth during a subsequent 24-hour simulated shipping period was monitored, as was plant growth during a subsequent growth cycle. One percent to 2% O2 for 12 or 24 hours limited radicle elongation to <1.0 mm during the simulated shipping period (darkness, ambient O2) and caused no permanent damage to seedlings. Suppression of radicle elongation with low O2 was greater with a 24-hour than a 12-hour exposure. Oxygen at 0% for 24 hours or at 0% to 1.5% O2 for 48 hours damaged seedlings irreversibly. These results show that specific subatmospheric O2 treatments can restrict radicle elongation of germinated seeds during subsequent shipment to a grower and that the low O2 treatment does not decrease subsequent plant growth.

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Mehrassa Khademi, David S. Koranski, David J. Hannapel, Allen D. Knapp, and Richard J. Gladon

Water uptake by impatiens (Impatiens wallerana Hook. f. cv. Super Elfin Coral) seeds was measured as an increase in fresh weight every 24 hours during 144 hours of germination. Seeds absorbed most of the water required for germination within 3 hours of imbibition and germinated at 60% to 67% moisture on a dry-weight basis. Germination started at 48 hours and was complete by 96 hours at 25C. Water stress of -0.1, -0.2, -0.4, and -0.6 MPa, induced by polyethylene glycol 8000, reduced germination by 13%, 49%, 91%, and 100%, respectively, at 96 hours. Under the same water-stress conditions, increases in fresh weight were inhibited by 53%, 89%, 107%, and 106%, respectively. Three distinct groups of storage proteins were present in dry seed; their estimated molecular weights were 1) 35, 33, and 31 kDa; 2) 26, 23, and 21 kDa; and 3) two bands <14 kDa. Major depletion of storage proteins coincided with the completion of germination. Water potentials that inhibited germination also inhibited degradation of storage proteins. During germination under optimum conditions, the soluble protein fraction increased, coinciding with a decrease in the insoluble fraction.