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David R. Dreesen and Robert W. Langhans

Uniformity of growth response of impatiens (Impatiems wallerana Hook. f.) plug seedlings was examined in four identical growth rooms. Differences among growth rooms for dry weight, height, and leaf area of 10- to 24-day-old seedlings were generally not significant. During six experiments over 6 months, an individual growth room was maintained under contant baseline environmental conditions. Differences in growth response over time appear to be related to nutrition and irradiance levels. For three experiments with nearly identical irradiance, temperature, and nutrition levels, dry weight and height growth differences over time were only rarely significant. These results illustrate that rather unsophisticated growth rooms can provide consistent growth response over time among experimental units.

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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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Brian A. Krug, Brian E. Whipker, Jonathan Frantz, and Ingram McCall

Reports of distorted terminal growth of pansy, petunia, and gerbera plants have become more prevalent, specifically in plugs grown in the high heat and humidity conditions of summer. The problem, considered to be a deficiency of calcium (Ca) or

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George Lazarovits

Plant growth-promoting rhizobacteria (PGPR) enhance plant development by many mechanisms. Indirect growth effects result from PGPR activities that displace soilborne pathogens and thereby reduce disease. Direct effects include improved nutrition, reduced disease due to activation of host defenses, and bacterial production of phytohormones. An understanding of the mode of action is essential for exploitation of PGPR for field use. For instance, bacteria that act as biological control agents can only be of benefit at locations where disease occurs. PGPR that stimulate plant growth directly will likely have more universal uses and greater impacts. Thus, we have been developing model systems for identifying PGPR with such traits. In this presentation, the effects of bacterization of tissue culture-grown plants, plug transplants, and seed with a growth-promoting Pseudomonas sp. (PsJN) will be described. Potential uses for this and other PGPR will also be identified. The talk will consider the advantages and limitations of: a) screening methods used for selection of PGPR, b) model systems available for studying the mechanisms of action, and c) why transplants offer an ideal delivery system for rhizobacteria. Results from field trials with PGPR with different modes of action will be presented and their future role in agriculture considered.

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M. P. Kaczperski and A. M. Armitage

The effects of differing storage conditions prior to transplanting were examined for Salvia splendens `Red Hot Sally', Impatiens wallerana `Super Elfin White', Viola × wittrockiana `Universal Beaconsfield' and Petunia × hybrida `Supercascade Lilac'. Plug-grown seedlings were stored for 0, 1, 2 or 3 weeks at 5C or 10C and irradiance levels from incandescent bulbs at 0, 2 or 12 μmol s-1 m-2. A second group of plants were stored at 18C and irradiance from fluorescent bulbs at 105 μmol s-1 m-2 for the same time period. Temperature was more important than irradiance in maintaining plant quality over the storage period. Impatiens and salvia could be stored successfully for a minimum of 2 weeks at 5 or 10C with no appreciable loss of quality, petunia and pansy up to 3 weeks. Seedlings of all species showed diminished quality when stored longer than 1 week at 18C. After storage, petunias stored at 18C flowered sooner than those stored at 5 or 10C. However, these plants were single stemmed, with long internodes and few flowers while those plants stored at 5 or 10C developed multiple branching and a short, compact growth habit at flowering.

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M.P. Kaczperski and A.M. Armitage

The effects of storage conditions before transplanting were examined for Petunia × hybrida Vilm. `Supercascade Lilac', viola × wittrockiana Gams `Universal Beaconsfield', and Salvia splendens F. Sellow ex Roem. & Schult `Red Hot Sally'. Plug grown seedlings were stored for 0, 7, 14, or 21 days at 5 or 10C and with continuous irradiance levels from incandescent bulbs at 0, 2, or 12 μmol·m-2·s-1. A second group was stored at 18C with irradiance from fluorescent bulbs at 105 μmol·m-2·s-1 and a 16-hour photoperiod for the same durations. Temperature was more important than irradiance in maintaining a commercially acceptable plant during the storage period. Petunia and pansy could be stored successfully for 21 days at 5 or 10C with no appreciable loss of quality; salvia could be stored for a minimum of 14 days. Seedlings of all species elongated excessively when stored >7 days at 18C and 105 μmol·m-2·s-1 irradiance. After 14 days of storage, petunias stored at 18C flowered sooner than those stored at 5 or 10C but time in a production environment (days to flower - days in storage) was similar for petunias stored at 5 or 18C.

Open access

J.D. Fry and P.H. Dernoeden


Little research has been conducted to determine the influence of fertilizer sources and rates on zoysiagrass (Zoysia japonica Steud.) establishment. Our objectives were to determine the influence of slow-release N sources, water-soluble N from urea, and N, P, and K combinations on rate of zoysiagrass establishment. Prior to field planting of zoysiagrass plugs, N rates of 98, 196, and 392 kg·ha-1 from ureaformaldehyde (UF, 38N-0P-0K), isobutylidine diurea (IBDU, 31N-0P-0K, and a composted sewage sludge (1.0N-0.9P-0.2K) were incorporated into a soil with existing high P (193 kg·ha-1) and intermediate K levels (86 kg·ha-1). In a separate study nitrogen from urea (46N-0P-0K, 195 kg·ha-1), P from treble superphosphate (0N-19P-0K, 126 kg·ha-1) and K from muriate of potash (0N-0P-32K, 103 kg·ha-1) also were incorporated before planting. Five months after planting, none of the slow-release N sources or N-P-K combinations had enhanced coverage of the zoysiagrass. No additional fertilizer was applied in the 2nd year. Although statistically significant differences were found among treatments by the end of the 2nd growing season, the actual increases in zoysiagrass coverage provided by the fertilizers were no greater than 5% more than the unfertilized zoysiagrass. In a 3rd study, N (49 kg·ha-1) from urea, applied as a topdressing either once, four, or seven times annually, resulted in a negative linear [coverage = 63.8 − 0.02 (kg N/ha per year), r 2 = 0.57] response in zoysiagrass coverage the initial year, but not in the 2nd year. Nitrogen from urea (49 kg·ha-1) applied bimonthly or monthly the 2nd year had a greater beneficial effect on zoysiagrass growth than topdressing or preplant incorporation of N the initial year.

Open access

Joshua K. Craver, Krishna S. Nemali, and Roberto G. Lopez

. Upon hypocotyl emergence, seedlings were irrigated with 16N–0.94P–12.3K water-soluble fertilizer (Jack’s LX Plug Formula for High Alkalinity Water; J.R. Peters, Allentown, PA) providing (mg·L −1 ): 100 N, 10 P, 78 K, 18 Ca, 9.4 Mg, 0.10 B, 0.05 Cu, 0

Free access

Toshio Shibuya, Yoshiaki Kitaya, Toyoki Kozai, and Masaichi Nakahara

Net photosynthetic and evapotranspiration rates of tomato (LAI = 2.3) and lettuce (LAI = 6.6) plug sheets were estimated based on measurements of the weight of plug sheets and vertical profiles of CO2 concentration above the plug sheets. The measurements were continued in situ for several days in a greenhouse when plugs were at transplant stage. The maximum net photosynthetic rates of tomato and lettuce plug sheets were 0.8 and 2.0 mg CO2/m2 per sec on a plug sheet area basis, respectively. The maximum evapotranspiration rates of those sheets were 100 mg·m–2·s–1. Net photosynthetic and evapotranspiration rates of tomato and lettuce plug sheets increased linearly with an increase in solar radiation flux, with a correlation coefficient of 0.9.

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Jeff S. Kuehny, Aaron Painter, and Patricia C. Branch

Plug production has increased the finished quality and uniformity of bedding plants, making them one of the most important greenhouse crops grown. The wide range of cultural practices used by different growers to produce plugs, may influence the efficacy of plant growth regulators applied to the same crop in postplug production. Ten bedding plant species were grown from plugs obtained from two sources using different cultural practices. The plugs were transplanted to jumbo six packs and sprayed with either chlormequat/daminozide tank mix, ancymidol, or paclobutrazol at three concentrations at three times of year. The effect of each plant growth regulator varied by plant species and time of year applied. Source of plug material did have a significant effect on height and time of flowering of finished bedding plants and the use of plant growth regulators did not minimize the differences in height between sources in most cases.