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Ross E. Byers

Ethephon applied 12 to 26 days after full bloom at 1000 to 1500 mg·liter-1 not only substantially inhibited apple (Malus domestia Borkh., spur `Delicious' strains) tree growth but also caused fruit abscission. Gibberellin plus ethephon did not prevent fruit abscission when ethephon was used at these rates. Several low weekly doses of ethephon controlled tree growth without causing fruit abscission. Ethephon increased fruit soluble solids concentration and substantially reduced fruit starch in the application year. Ethephon greatly increased flowering and fruit set the following season. Fruit length: diameter ratio was not altered by the previous seasons' low weekly doses of ethephon. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).

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Tao Yuan, Qiuying Wei, and Gary Bauchan

regulator treatments, especially those including gibberellin ( Cadman et al., 2006 ). Germination of P. cernua seeds can increase to >92% if they are treated with kinetin, gibberellin GA3, and 2, 4-D for 24 h compared with 18% in untreated controls ( Gu et

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Yong-Ping Gao, Hino Motosugi, and Akira Sugiura

Ungrafted trees of seven apple rootstock cultivars, M.4, M.7, M.11, M.26, M.27, MM.106, and Maru. bakaidou (Malus prunifolia Borkh. var. ringo Asami; weeping type), and `Fuji' (Malus domestics Borkh.) trees grafted on these seven plus M.9 and M. 16 rootstock were grown in sand. They were regularly supplied with nutrient solutions of N as ammonium alone (A), nitrate alone (T), and both (AT). With both ungrafted and grafted trees, the shoot growth of six rootstock (M.11, M.4, M.7, MM.106, M.26, and M.27) was significantly less with A than with T. With `Fuji' trees grafted on the above six rootstock, the number of flowering buds and the ratios of flowering buds to total emerged buds were significantly enhanced by treatments A and AT, especially in the formation of axillary flowering buds. Flowering and shoot growth of `Fuji' trees grafted on M. prunifolia and M.16 were slightly affected by the form of supplied N. In the xylem sap, cytokinin-like activity was detected in a single zone in paper chromatography in all rootstock and `Fuji' trees. The activity in six ungrafted rootstock (M.4, M.7, M.11, M.26, M.27, and MM.106) and `Fuji' trees grafted on these plus M.9 rootstock were higher with A than with T. Gibberellin-like activity in the same sap was detected in two zones, Rfs 0.3 to 0.4 and Rfs 0.7 to 0.8 in paper chromatography. In the six ungrafted rootstock and in `Fuji' trees grafted on these plus M.9, A led to higher activity at Rfs 0.7 to 0.S, but T led to higher activity at Rfs 0.3 to 0.4. Cytokinin-like and gibberellin-like activities in ungrafted M. prunfolia and `Fuji' trees grafted on M. prunifolia or M.16 were not affected by the form of N.

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R.E. Byers, D.H. Carbaugh, and C.N. Presley

data; a bbott Laboratories (gibberellin), Miller Chemical Co. (Vapor Gard), and Uniroyal (daminozide) for chemical supplies: and to the Virginia State Horticultural Society and a bbott Laboratories for partial financial assistance. The cost of

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Aneta K. Studzinska, David S. Gardner, James D. Metzger, David Shetlar, Robert Harriman, and T. Karl Danneberger

duration, are in part mediated by gibberellins (GAs) ( Hedden and Kamiya, 1997 ; Sponsel and Hedden, 2004 ). GAs are phytohormones that are involved in many developmental processes including stem elongation ( Davies, 2007 ). GAs act by inducing genes

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Brent L. Black and Mark K. Ehlenfeldt

applications of a plant growth regulator would provide a low-labor, low-cost method to suppress flowering. Foliar applications of commercially formulated gibberellin (GA 3 ) are now a common industry practice in tart cherry production to prevent precocious

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Alexander D. Pavlista, Dipak K. Santra, James A. Schild, and Gary W. Hergert

, to raise lower pods higher off the ground and allow the cutting blades on a direct harvester to cut the stem below those pods. This may be accomplished by application of a growth-stimulating compound such as GA 3 . The ability of gibberellins to

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Abraham H. Halevy, Eitan Shlomo, and Ofra Ziv

Experiments aiming to adapt the perennial balloon flower (Platycodon grandiflorus) as a commercial cut flower crop were conducted for 4 years under various growing conditions: four controlled-temperature rooms at two photoperiods in a phytotron, heated and unheated greenhouses, and a saran net-house (15% shade). Best flower yield was obtained following crown cooling for 12 weeks at 2 to 4 °C. Platycodon is a day-neutral plant, but produce more flowering stems under long days. Flower initiation and development is enhanced with increased growing temperature from 17/12 °C (day/night) to 27/22 °C. At very high temperatures (32/24 °C), however, only a few flowers are formed. Best quality stems were produced at 12 to 14 °C night temperature. At higher night temperatures, flowering stems were thin and weak. Gibberellin treatments to the crowns and the plants did not affect flowering time. Chemical name used: gibberellin (GA3).

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Bo Meyering, Adam Hoeffner, and Ute Albrecht

plant internal conditions ( Simpson and Dean, 2002 ). Bioactive gibberellins (GA) are a class of endogenous phytohormones that positively direct seed germination, stem elongation, and floral initiation and significantly interact with the auxin

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Richard L. Harkess and Robert E. Lyons

BA and GA4+7, were applied to vegetative, mature Rudbeckia hirta plants at the beginning of long days (LD). There were no synergistic effects, but BA inconsistently affected branching and had no effect on flowering. Floral initiation of the terminal inflorescence was promoted by GA4+7, although axillary inflorescences were not. Increasing GA4+7 levels decreased the time to terminal inflorescence anthesis. However, the interval between the terminal and second axillary inflorescence anthesis was increased. The net result was no significant effect on the time to second axillary inflorescence anthesis. Gibberellins may enhance the LD effect on the apical meristem of Rudbeckia, but axillary meristems, which initiate later, remained unaffected. Chemical names used: benzyladenine (BA), gibberellin4+7, (GA4+7).