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Susan S. Han

Effects of the duration of cold storage, as well as the concentrations, timing, and means of application of a growth regulator solution on the postharvest quality of cut Oriental and Asiatic lilies were evaluated. Without cold storage, lower leaves of Oriental lily `Stargazer' began to turn yellow ≈1 week after placing stem in an interior environment. The development of leaf yellowing continued to progress upward until the end of the vase life when there was an average of >25% chlorotic leaves. Cold storage worsened the leaf disorder. The longer the duration of cold storage, the earlier the development of leaf yellowing and the higher the percentage of leaves that were chlorotic. Spraying leaves with a solution containing 25 mg·L-1 each of BA and GA4+7 significantly reduced cold-storage-induced leaf yellowing and bud abortion in both Oriental and Asiatic lily. Concentration of the growth regulator solution was inversely related to the development of leaf yellowing. Timing of the growth regulator application was not critical, as there were no differences in leaf yellowing or bud development when the growth regulator solution was sprayed before or after the cold storage. Addition of the growth regulators to the preservative solution completely prevented leaf yellowing but also induced bud abortion. For practical application, spraying growth regulators prior to or after the cold storage would significantly improve the postharvest quality of cut lilies.

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Wayne L. Schrader

Three trials were conducted in 1989 to evaluate the effects of chilling, freezing, growth regulator, and acid scarification treatments on the seed germination of two artichoke varieties. Soaking seed in a 500, 1000, or 2000 ppm ethephon solution for 5 minutes significantly increased the rate and uniformity of germination. Chilling, freezing, gibberellin, and cytokinin treatments did not affect germination rate. Freezing moistened seed and acid scarification significantly delayed germination. Ethephon treatments did not affect subsequent seedling development.

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Patrick E. McCullough, Haibo Liu, Lambert B. McCarty and Ted Whitwell

Dwarf bermudagrass morphological characteristics following the use of plant growth regulators have not been reported. The objective of this greenhouse study was to determine short-term effects of seven plant growth regulators on clipping yield, chlorophyll concentration, and root mass of `TifEagle' bermudagrass. Growth regulators tested included ethephon, fenarimol, flurprimidol, maleic hydrazide, mefluidide, paclobutrazol, and trinexapac-ethyl. Two applications of each compound were made over a 6-week period. Root mass was reduced 39% by fenarimol and 43% by flurprimidol, while other PGRs had root mass similar to untreated turf. `TifEagle' bermudagrass treated with paclobutrazol, mefluidide, fenarimol, and flurprimidol averaged 45% less root mass than trinexapac-ethyl-treated turf. Trinexapac-ethyl was the only compound to reduce clippings and enhance turf quality without negative rooting effects. Chemical names used: [4-(cyclopropyl-[α]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester] (trinexapac-ethyl); {α-(1-methylethyl)-α-[4-(trifluoro-methoxy) phenyl] 5-pyrimidine-methanol} (flurprimidol); (+/-)-(R*,R*)-β-[(4-chlorophenyl) methyl]-α-(1, 1-dimethyl)-1H-1,2,4,-triazole-1-ethanol (paclobutrazol); (N-[2,4-dimethyl-5 [[(trifluoro-methyl)-sulfonyl] amino]phenyl]acetamide) (mefluidide); [1,2-dihydro-3,6-pyridazine-dione] (maleic hydrazide); [(2-chloroethyl)phosphonic acid] (ethephon); and (2-(2-chlorophenyl)-2-(4-chlorophenyl)-5-pyrimidinemethanol) (fenarimol).

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Miklos Faust

At the beginning and near to the end of the endodormant period, cytokinin-type growth regulators are effective to end dormancy in apple. The same growth regulators are not effective during the middle of this period. Terminal buds require less chilling than lateral buds to emerge from the dormant period. Lateral buds on decapitated shoots also require less chilling, indicating that auxin may be involved in dormancy. Replacing the terminal with IAA keeps water in bound state in the lateral buds, indicating the effect of IAA in dormancy. We have developed the theory that the beginning and the end of the winter-dormant period is governed by apical dominance. It appears that only this period can be manipulated either with dormancy avoidance methods or with dormancy-breaking chemicals. The central portion of the dormant period is not subject to manipulation. Therefore, it is important that the depth of the dormancy is quantified. Certain growth regulators can be used for determining the state of bud dormancy. Thidiazuron gives results within 2 to 4 days.

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Susan S. Han

Leaf yellowing of excised Easter lily leaves was significantly delayed by application of gibberellic acids ≥250 mg·liter-1 or benzyladenine ≥50 mg·liter-1. Rapid development of foliar chlorosis following cold storage was delayed significantly by applying 500 mg·liter-1 of GA3 or BA before storage. Poststorage treatments were less effective. Development of chlorosis was associated with rapid loss of fresh weight and was not related to the aperture of the stomates (diffusive resistance). Respiration rates of leaves treated with growth regulators were significantly lower than those of the controls.'

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Marco Volterrani, Nicola Grossi, Monica Gaetani, Lisa Caturegli, Aimila-Eleni Nikolopoulou, Filippo Lulli and Simone Magni

seeding is routinely adopted for several field crops. Properly sized sprigs could fit precision seeding machinery thus with the potential of being planted at a defined depth and spacing. Plant growth regulators (PGRs) are known for their ability to modify

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Martin J. Bukovac

The importance of spray application and the role of spray additives are reviewed in reference to increasing the effectiveness of plant growth regulators (PGR). The spray application process is composed of a number of interrelated components, from formulation of the active ingredient into a sprayable, bioactive solution (emulsion/suspension), to atomization, delivery, retention, and penetration into the plant tissue. Each of these events is critical to performance of the PGR. Also, each can be affected by spray additives, particularly adjuvants, which may be incorporated in the formulation of the active ingredient or added to the spray mixture. The role of the individual components and effects of spray adjuvants, particularly surfactants and fertilizer adjuvants, on the component processes are discussed.

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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.

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Kenneth C. Sanderson

Cuttings (3 per 1.5-liter pot) of `Annette Hegg Lady' and `V-14 Glory' poinsettias were directly rooted under mist and subsequently grown for treatment with various growth regulator sprays. Sprays of 40 ppm and 61 ppm paclobutrazol, 2,500 ppm daminozide plus 1,500 chlormequat, 20 ppm and 40 ppm ethephon, 150 ppm ancymidol, 5,000 ppm daminozide, 20 ppm and 40 ppm uniconazole, and 25 ppm and 50 ppm flurprimidol were applied to the plants with a low pressure, high volume sprayer on October 23. Sprays of 40 ppm uniconezole caused the most height retardation with both cultivers, however 4000 ppm ethephon, 20 ppm uniconazole and 61 ppm paclobutrazol often gave comparable height retardation. Bract area of both cultivars was most severely retarded by 40 ppm uniconazole and 4,000 ppm ethephon.

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William J. Carpenter and Eric R. Ostmark

The storage and germination environments were evaluated to determine the cause of low total germination percentages and highly irregular germination of Coreopsis lanceolata L. seed. Highest total germination and most rapid and uniform germination of seed occurred at constant 15C, other constant temperatures and all alternating temperature regimes caused lower total germination or delayed it. Seeds tolerated -20C during storage, but total germination was reduced below -5C. Recently harvested seeds had 44% total germination, but 54% to 81% germination was achieved after 6 hours of soaking seeds in 1000 ppm GA3, 1000 ppm ethephon, or 25 ppm kinetin alone or in combination. Growth regulators reduced the number of days to 50% of final germination (T50), and the span in days between 10% and 90% of germination (T90 - T10). Storing fresh seeds without chemical treatment for > 6 months at 5C and 10% to 20% relative humidity (RH), or 15C at 20% to 35% RH, increased total germination to 75% and 80%, respectively. Ten days were required to achieve T50 after 5 to 6 months of storage at 5C and 10% to 20% RH or 15C and 10% to 40% RH, with longer periods to T50 at other storage durations and RH levels. The germination spans (T90 - T10) were lengthened the higher the seed storage temperatures between 5 to 25C, with longer spans as seed storage durations and relative humidities increased. Total germination was similar after storing seeds at 5 or 15C and 10% to 30% RH and after soaking recently harvested seeds in GA3 + ethephon, but the days to T50 and T90 - T10 were shorter after growth regulator treatment. Chemical names used: (2-chloroethyl) phosphonic acid (ethephon); gibberellic acid (GA3); 6-furfurylaminopurine (kinetin).