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Mahmoud R. Shedeed, Khairy M. El-Gamassy and Alaa M. Almulla

The experiment was designed to investigate the effect of Fulifertil at levels 0,2 and 4 gm/L and growth regulators GA3 at 0,100,200 and 300 ppm also kinetin at 0,25,50 and 75 ppm and their combination on croton plants. In general the results indicate that there were increases in the carbohydrates, nitrogen, phosphorus and potassium content. The anthocyanins and carotenoids pigments were increased while chlorophyll `a” and “b” pigments were decreased. These findings are required to give colorful leaves which give good display.

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Aristidis S. Matsoukis, Ioannis Tsiros and Athanasios Kamoutsis

identification of the experimental plants.

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Billy J. Johnson

Two separate experiments (one and two applications and dates of treatment) were conducted on plant growth regulator (PGR) injury and seedhead suppression of centipedegrass [Eremochloa ophiuroides (Munro) Hack.]. Mefluidide caused less injury to centipedegrass than either imazethapyr or flurprimidol + mefluidide. Mefluidide applied at 0.56 kg·ha-1 in each of two applications at 2-week intervals suppressed seedheads of centipedegrass for 10 weeks. A single 0.56-kg·ha-1 application of the mefluidide failed to suppress seedheads when applied any time from mid-June until late July. A single treatment with flurprimidol + mefluidide severely injured centipedegrass, and seedhead suppression was poor regardless of date of treatment. Centipedegrass was severely injured when flurprimidol + mefluidide was applied at 1.68 + 0.28 kg·ha-1 in each of two applications, but seedheads were suppressed for 10 weeks. Imazethapyr applied at 0.30 and followed by 0.15 kg·ha-1 suppressed seedheads 10 weeks after treatment in 1987 and 6 weeks after treatment in 1988 without reducing turf density. When this PGR was applied as a single treatment at 0.30 kg·ha-1, seedhead suppression was generally greater for 8 weeks when applied mid- to late July than mid- to late June. Chemical names used: N-[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl]amino]phenyl]acetamide (mefluidide); α -(1-methylethyl)- α -[4-(trifluoromethoxy)phenyl]-5-pyrimidinemethanol (flurprimidol); and (±)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-ethyl-3-pyridinecarboxlic acid (imazethapyr).

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Seung-Hyun Kim, A.A. De Hertogh and P.V. Nelson

Two experiments were conducted to determine the effects of applied ancymidol, chlormequat, daminozide, paclobutrazol, and uniconazole on early spring (March) and late (May) spring forcing of Dutch-grown Bleeding Heart [Dicentra spectabilis (L.) Lem.] as a flowering pot plant. Most of the plant growth regulator (PGR) treatments delayed flowering, however, the average time to flower after planting was from 17 to 21 days for untreated plants and delays were only 3 to 6 days with PGR treatments. Thus, the effect is not important commercially. Acceptable plant quality and height control not only at flowering but also 14 days later was obtained with two sprays of 3000 mg·L-1 (ppm) daminozide or two sprays of 50 mg·L-1 paclobutrazol. Uniconazole reduced total plant height, however, because the inflorescence did not elongate, plant quality was greatly reduced. Most ancymidol sprays were phytotoxic producing a chlorosis of the leaf margins. Media drenches of ancymidol or chlormequat did not control total plant height. Sprays and media drenches of ancymidol, daminozide, paclobutrazol, and uniconazole produced plants with a very deep green leaf color, but chlormequat did not. The total number of shoots per tuberous root, the number of shoots with flowers, and stem strength were not significantly affected by PGR treatments. If the tuberous roots have been properly cold treated, they initiate growth rapidly after planting. Thus, the first PGR spray must be applied immediately after shoot growth is initiated, which was 6 to 8 days after planting, followed by a second spray 5 days later. Two applications are necessary because of uneven shoot emergence and growth from the tuberous roots.

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E.W. Stover and D.W. Greene

Plant response to foliar application of plant growth regulators (PGRs) is often variable, in part due to environmental factors. Weather prior to application is thought to influence cuticle development and thus PGR uptake. For example, in growth chamber studies foliar uptake of 1-naphthaleneacetic acid (NAA) is sometimes increased when fruit trees are placed in low temperature and high humidity several weeks prior to application. Environmental conditions over an extended period of time after application may influence PGR conversion to active form (e.g., ethephon), PGR metabolism, or metabolic factors that affect PGR activity in the plant. The effects of environmental conditions on PGR uptake have been investigated extensively in laboratory studies. In many cases, uptake is clearly increased by high temperatures immediately after application. Laboratory studies report a linear positive correlation between temperature and uptake and greater temperature response above 25 °C (77.0 °F). High humidity and longer drying time often are also reported to increase PGR uptake in laboratory studies. These results are consistent with many grower observations on effects of weather on chemical thinning and have been incorporated into many product labels and extension recommendations. However, relatively few field experiments have been reported in which the relationship between PGR response and environmental conditions were assessed. Wash-off studies have demonstrated that rain shortly after application may reduce efficacy of NAA. Several studies demonstrate environmental interaction with metabolic activity involved in PGR action. For example, shading after thinner application is reported to increase fruitlet abscission and enhance effectiveness of some thinning agents. Chemical thinning of apples (Malus ×domestica) with ethephon is reported to correlate strongly with temperature in the days after application, while studies suggest that higher temperatures after aminoethoxyvinylglycine (AVG) application may reduce control of preharvest drop. However, the stage of fruitlet development at apple thinning often appears to be more important than environmental conditions at the time of PGR application. In addition, field experiments indicate that longer drying times at lower temperatures seem to largely compensate for greater uptake rates at higher temperatures. This paper discusses data from published and previously unpublished experiments in order to understand the effects of environment on PGR response variability.

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Amy Lynn Bartel and Terri W. Starman

Angelonia angustifolia `Blue Pacific', Asteriscus maritimus `Compact Gold Coin', and Heliotropium aborescens `Fragrant Delight' are three vegetatively propagated species of annuals. The objective of this study was to find which plant growth regulator chemicals could be used to control height and produce compact, well-branched, flowering plants. The plants arrived as rooted plugs and were transplanted to 10-cm plastic containers. When the roots of the transplanted plugs reached the edge of their containers, 15 days after transplanting, the plant growth regulator chemicals were applied. Five different chemicals were used in spray applications at two rates measured in mg/L: ancymidol at 66 and 132; daminozide at 2500 and 5000; paclobutrazol at 20 and 40; ethephon at 500 and1000; and uniconazole at 10 and 20. One drench application of uniconazole at 1 and 2 mg/L and one control (water spray) were also used. Total plant height, plant width, flower number, node number, stem length, internode length, and numbers of days to visible bud were recorded. Ancymidol at both rates caused stunting and flower distortion in asteriscus; however, it was not effective on angelonia or heliotrope. Paclobutrazol and uniconazole sprays were ineffective in controlling height on all three species. Ethephon at both rates was effective in controlling height, and producing well-branched plants in all three species, yet it caused a delay in flowering. Uniconazole drench at both rates was also effective in controlling height but caused stunting. In general, daminozide at 5000 mg/L was most effective in controlling foliage height without a delay in flowering or decrease in flower size or number in all three species.

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Y.D. Park, H.S. Kim and B.K. Kang

The development of genetic transformation systems has led to remarkable progress in the area of plant molecular biology. This has included the introduction of useful traits, such as resistance to viruses, herbicides, and insects. Transformed plant cells can be selected, using chimeric genes that confer resistance to toxic drugs, such as kanamycin, hygromycin, streptomycin, gentamycin, and bleomycin. Expression of these chimeric genes in the transformed cells confers the ability to survive and proliferate on the selective medium, while non-transformed cells die. In this study, we report a simple and efficient system to regenerate Chinese cabbage plants and study of the effects of plant growth regulators, AgNO3, initial dark treatment, various antibiotics, and herbicide on shoot induction from hypocotyl or cotyledon of Chinese cabbage. Shoots were induced at various combinations of naphtalene acetic acid (NAA) and benzyladenine (BA) levels. The best combination of plant growth regulators was 2.0 mg/L NAA and 1.0 mg/L BA for cotyledon, and 1.0 mg/L NAA and 5.0 mg/L BA for hypocotyl. The experiment investigating the effect of AgNO3 demonstrated that 16.7 mg/L AgNO3 was effective for inducing shoot regeneration from both of explants. Three to five days of initial dark treatments had significant effects for increasing the number of regenerated shoots; however, different growth regulator combinations showed various responses to duration of dark treatments. The effects of kanamycin, hygromycin, cefatoxime, carbenicillin and phosphinothricin (PPT) on shoot induction from cotyledon and hypocotyl were tested. Shoot induction was completely inhibited by kanamycin at 10 mg/L, hygromycin at 5 mg/L, PPT at 5 mg/L or higher, but not by carbenicillin and cefatoxime.

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Jeffrey Adelberg, Maria Delgado and Jeffrey Tomkins

, plant dry weight (DW), and subsequent growth in the greenhouse ( Gollagunta et al., 2004 ). Sugar and water use estimates for targeted crops would be useful to guide scale-up to larger bioreactor vessels. Plant growth regulators influenced nutritional

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P.D. Petracek, F.P. Silverman and D.W. Greene

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Gamil A. Kabbabe and William J. Carpenter

Verbena seed when harvested, has a natural dormancy that gradually dissipates during a 5 to 8 month period of dry storage. In this study, the gradual loss of the dormancy causing factor was correlated with germination percentage. Acetone treatment of verbena seeds was found to cause a slight, but non-significant, reduction in total germination. However, the infusion of gibberellic acid (GA4/7) and kinetin (KIN) with the acetone at various concentrations improved germination. The traditional method of seed osmoconditioning using Polyethylene Glycol (PEG 8000) at -1.0 MPa caused a non-significant reduction in percent germination, similar to that with acetone. When growth regulators were mixed with the osmoconditioning solution, at the concentrations used with acetone, a definite and significant improvement in terms of rate and percent of germination was observed.