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Kristin L. Getter

The effects of paclobutrazol (PBZ), a plant growth retardant, and average daily temperature (ADT) on geranium (Pelargonium ×hortorum), petunia (Petunia ×hybrida), marigold (Tagetes erecta), and pineapple mint (Mentha suaveolens) were quantified. Treatments consisted of four PBZ spray concentrations (0, 15, 30, or 45 ppm) and three ADTs (constant day and night greenhouse temperatures set to 16, 22, or 28 °C). The effectiveness of PBZ was dependent on species. Greenhouse ADT was significant for all species for both growth index (GI) and dry weight (DW). Whether the GI or DW was impacted by the interaction between ADT and PBZ levels were also species dependent. As ADT increased, the trialed levels of PBZ were less effective. Three species (all but petunia) had a significant ADT and PBZ interaction for DW. The 0 ppm PBZ treatment for geranium exhibited a larger DW at 28 °C compared with 16 °C, whereas the 30 and 45 ppm PBZ treatments each had smaller DWs at 28 °C than at 16 °C. However, marigold and pineapple mint generally had larger DWs at higher ADTs than lower ADTs within a PBZ treatment.

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Iftikhar Ahmad, John M. Dole, Atyab Amjad, and Sagheer Ahmad

Effects of wet and dry storage methods were compared to improve postharvest performance of specialty cut flower species. While increasing duration of storage reduced vase life, vase life declined less with dry storage for marigold (Tagetes erecta) and rose (Rosa hybrida), but not for zinnia (Zinnia elegans) or lisianthus (Eustoma grandiflorum) over wet storage. Marigold stems had 1.9, 4.6, and 1.5 days longer vase life after 1, 2, or 3 weeks in dry storage, respectively, as compared with storage in water. Zinnia stems did not tolerate either wet or dry storage, while lisianthus stems had a longer vase life when stored in water as compared with dry storage. For rose, dry storage for 2 weeks increased vase life compared with wet storage. Dry stored marigold and lisianthus stems had higher water uptake after being placed in the vase as compared with the stems stored in water, while zinnia and rose had less uptake. Storage method had no effect on leaf relative water content (LRWC) in lisianthus, marigold, and zinnia; however, LRWC decreased with increased storage duration. This necessitates evaluation of storage method and duration effects for each species and cultivar to ensure extended storage life and improve postharvest quality.

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Jillene R. Summers, Gail R. Nonnecke, Cynthia A. Cambardella, Richard C. Schultz, and Thomas M. Isenhart

Improving soil quality and suppressing weeds are two challenges facing strawberry growers. Cover crops, such as perennial ryegrass (Lolium perenne) and sorghum-sudangrass (Sorghum sudanense), have been used in rotation with strawberry in the Midwest. The objective of the field study was to investigate the effects of various cover crops on soil quality and weed populations for strawberry production. The experiment was established in 1996 at the Iowa State Univ. Horticulture Station, Ames, in plots that previously were planted continuously in strawberry for 10 years. Nine treatments were arranged in a randomized complete-block design with three replications. Treatments included cover crops of Indian grass (Sorghastrum avenaceum), switchgrass (Panicum virgatum), big bluestem (Andropogon gerardii), black-eyed susan (Rudbeckia hirta), marigold (Tagetes erecta `Crackerjack'), sorghum-sudangrass, perennial ryegrass, strawberry (Fragaria ×ananassa `Honeoye'), and bare soil (control). Data from 1998 showed that both annual and perennial cover crops were established more readily (higher treatment-plant populations and less weed populations) than in 1997. Water infiltration rates were highest in bare soil plots and lowest in P. virgatum plots. Bare soil plots and S. sudanense plots had the lowest percent soil moisture.

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Jonathan M. Frantz*, Dharmalingam S. Pitchay, James C. Locke, and Charles Krause

Silica (Si) is not considered to be an essential plant nutrient because without it, most plants can be grown from seed to seed without its presence. However, many investigations have shown a positive growth effect if Si is present, including increased dry weight, increased yield, enhanced pollination, and most commonly, increased disease resistance, which leads to its official designation as a beneficial nutrient. Surprisingly, some effects, such as reduced incidence of micronutrient toxicity, appear to occur even if Si is not taken up in appreciable amounts. The literature results must be interpreted with care, however, because many of the benefits can be obtained with the counterion of the Si supplied to the plant. Determining a potential benefit from Si could be a large benefit to greenhouse plant producers because more production is using soilless media that are devoid of Si. Therefore, Si must be supplied either as a foliar spray or nutrient solution amendment. We investigated adding Si to New Guinea Impatiens (Impatiens hawkeri Bull), marigold (Tagetes erecta), pansy (Viola wittrockiana), spreading petunia (Petunia hybridia), geranium (Pelargonium spp.), and orchid (Phalaenopsis spp.). Using SEM, energy dispersive X-ray analysis, and ICP analysis, Si content and location was determined. This information and other growth characteristics will be used as a first step in determining the likelihood of using Si as a beneficial element in greenhouse fertilizer solutions for higher quality bedding plants with fewer agrochemical inputs.

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David A Gilbertz

Seven to 9 cvs each of Begonia semperflorens, Tagetes erecta, T. patula, and Petunia hybrida (grandiflora and multiflora types) were sown into seedling trays. One to 3 weeks after transplanting to flats (75 cm3/cell), paclobutrazol (PB) was sprayed at concentrations of 10 (begonia), 60 (marigold) or 100 (petunia) mg liter-1 at a 200 ml m-2 rate. Uniconazole (UC) was applied at one-half the PB concentrations. Plant height was measured before planting in the field May 17 and monthly through July. Species were analyzed separately and generally, there were no cultivar by triazole interactions. During the greenhouse phase, the triazoles controlled height of both marigold species compared to control, but in July the PB and UC treated plants were 100 and 91%, respectively, of control plant height. Flowering was delayed up to 4 days for UC treated T. patula plants. Height of triazole-treated petunias was 60-67% of control height during the greenhouse phase and 84-95% after 2 months in the field. Begonia height was reduced by triazoles during both phases. After 2 months in the field, PB and UC treated begonias were 72 and 44%, respectively, of control plant height.

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Nancy K. Todd

Marigolds are susceptible to a specific nutritional disorder known as “bronze speckling”. It has been reported that the disorder is caused by excessive uptake of iron by the plant, which may be due to high levels of Fe in the soil solution or low soil pH. In this experiment, 12 cultivars of marigold (Tagetes erecta and T. patula) were grown using increasing levels of Fe (0, 5, 15, and 20 mg/l) from Fe DTPA. In the susceptible cultivars, symptoms were observed within 5 days of initial treatment and appeared as a chlorotic mottling. Initial symptoms resembled spider mite damage on older leaves, which gradually became bronze colored in appearance, and finally became necrotic. Downward cupping of leaves was observed in severely affected plants. Severity of necrosis and percent of plant leaves affected (dry weight basis) were evaluated to determine susceptibility of the different cultivars to the disorder. There was a direct correlation between increasing concentration of Fe and occurrence and severity of symptoms. The most susceptible to least susceptible cultivars were determined to be: First Lady, Inca, Discovery, Galore, Pineapple Crush, Perfection Excel, Voyager All Seasons, Nugget, Zenith, Voyager F1 and Diamond Jubilee.

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Carl E. Niedziela Jr., Stephen A. Emerson, and Guochen Yang

Plug seedlings of Tagetes erecta L. `Gold Coin Mix' were planted in four production systems (harvest lugs, lay-flat bags, pots, and polystyrene trays) on 5 May 2005. Production systems were randomized in a Latin-square design with four replications of each system. Each treatment plot was 0.7 m × 1.1 m. Planting density was 31 plants/m2. The harvest lugs were 55 cm × 37 cm × 16 cm. The lay-flat bags were 114 cm × 30 cm × 3 cm. The pots were 25-cm bulb pans. The polystyrene trays were 67 × 34 × 5 cm and contained 32 square cells. All of the containers were filled with the same tobacco germination media. The plants in the harvest lugs, lay-flat bags, and pots were irrigated on alternate days with 150 mg·kg-1 N from 20N–4.4P–16.6K. The plants in the polystyrene trays were floated on a solution of 150 mg·kg-1 N from 20N–4.4P–16.6K. Float solutions were monitored and adjusted weekly for volume and fertilizer concentration. Individual stems were harvested at the appropriate stage of development for market. The fresh weight, stem length, and dry weight of individual stems were recorded. The rate of growth and maturation differed between production systems and locations in the greenhouse. Detailed results will be presented.

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Marc W. van Iersel and Krishna S. Nemali

We examined the effectiveness of an elevated capillary mat system to maintain constant and different moisture levels in the growing medium and verify the potential of drought stress conditioning in producing small and compact bedding plants. To differentiate between plant height and compactness, we determined compactness as the leaf area or dry mass per unit stem length. Marigold `Queen Sophia' (Tagetes erecta L.) seedlings were grown in square, 9-cm-wide, 10-cm-high containers filled with a soilless growing medium. A capillary mat was laid on top of a greenhouse bench which was raised by 15 cm on one side compared to the other side to create an elevation effect. Seedlings were subirrigated by immersing the low end of the capillary mat in a reservoir of water. The amount of water moving to the higher end of the mat progressively decreased with elevation. The moisture content in the growing medium averaged from 26 to 294 mL/pot at different elevations. Regression analysis indicated that growth parameters including, shoot dry mass, leaf area, leaf number, and plant height decreased linearly with decreasing soil moisture content in the growing medium. Of all the measured growth parameters, plant height was found to be least sensitive to decreasing moisture content in the growing medium. Plants in high moisture treatments had more dry mass and leaf area per unit length of the stem compared to those in low moisture treatments. Our results indicate that drought stress can produce small, but not truly compact bedding plants.

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Arvazena E. Clardy and Stephen Garton

Two cultivars of Tagetes erecta Marigolds—Hero Yellow and Safari Tangerine—were grown hydroponically in two different nutrient solutions. The experiment was implemented in the greenhouses on the campus of Alabama A&M Univ., from March to May 1995. The experiment was to assess the effects of growth and development of Marigolds. Heights of seedlings, germinated in grodan (rockwool) cubes were measured and placed randomly in the hydroponic units. Plants were drenched with five rates of either Paclobutrazol (Bonzi) and Uniconazole (Sumagic). The experiment was laid out as a randomized complete block design with either three or four replications of the treatment, which were factorial combinations of variables. After 75 days measurements were made of plants heights, flower bud numbers and dry weights of shoot and root systems. Shoot dry weights were affected by growth regulator treatments, variety, nutrient treatments and a combination of variety and nutrient treatments. Root dry weights were affected by nutrient treatments. Flower bud formation and numbers were affected by the combination of nutrient and variety. Heights were affected by growth regulator treatments, variety and nutrient treatments.

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Joseph P. Albano and Donald J. Merhaut

The objectives of the study were to determine effects of iron (Fe) source on plant growth, plant nutrition, substrate chemistry, and runoff chemistry. Iron source (FS) treatments consisted of Fe-aminopolycarboxylic acid (APCA) complexones iron ethylenediaminetetraacetic acid (FeEDTA), iron [S, S′]-ethylenediaminedisuccinic acid (FeEDDS), iron diethylenetriaminepentaacetic acid (FeDTPA), and iron ethylenediaminedi(o-hydroxyphenylacetic) acid (FeEDDHA) and non-chelated iron sulfate (FeSO4) added to a base nutrient solution at the rate of 1 mg·L−1 Fe final concentration. Marigold (Tagetes erecta) ‘First Lady' was grown in peat-based media fertilized with FS treatments over a period of 22 d. Iron source treatments were nonsignificant for foliar Fe, manganese (Mn), or zinc (Zn) averaging 162 μg·g−1 Fe, 228 μg·g−1 Mn, and 35 μg·g−1 Zn but were significant for foliar copper (Cu). Main effect of FS on pour-through (PT) leachate pH was statistically different but not practically significant, averaging 6.42. The FeDTPA treatment resulted in higher levels of Cu, Fe, and Zn in PT extracts. Leachate-runoff (LR) was collected and analyzed over the course of the study. Results of LR were similar to PT with levels of Cu, Fe, and Zn for the FeDTPA treatment resulting in higher concentrations of these metals. In both PT and LR, the highest concentration of Mn was associated with the FeEDTA treatment. Spectrophotometer analyses of PT and LR leachates determined the presence of all Fe chelates tested in those solutions.