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M.M. Jenderek and A.J. Olney

The ability of Hibiscus syriacus explants to produce regenerable callus was investigated. Fragments of cotyledons, hypocotyl, and roots were cultured on MS media supplemented with two different auxins (2,4-D and NAA, both 0.3 mg/L) and three different cytokinin (BA, 2iP and kinetin, all 0.1 mg/L). Plants were regenerated on McCown media with three different cytokinins at two different concentrations (0.1 and 1.0 mg/L). The biggest volume of callus was produced on medium containing 2,4-D/2iP (2,821 mm3/explant). The smallest mass of callus was induced on medium with NAA/kinetin (120 mm3/explant). On BA-supplemented media, the auxin type had no significant influence on the amount of callus produced. The highest number of shoots and leaves was produced on callus induced on NAA/BA supplemented media and regenerated on medium with 0.1 mg/L BA (4.2 shoots and 20 leaves/explant). Callus cultured on medium with 1.0 mg/L of BA produced significantly less shoots (2.4 shoots/explant). The lowest number of shoots was observed on callus originating from NAA/kinetin and NAA/2iP callus media and grown on medium with kinetin or 2ip (both 1.0 mg/L). The highest number of roots was produced by cultures originating from NAA/BA callus medium grown on the BA regeneration medium, irrespective of the cytokinin level. The longest shoots were observed on medium supplemented with 1.0 mg/L BA (18 mm). In this study, the best plant regeneration results were obtained for callus initiated on NAA/BA supplemented medium and regenerated on medium with 0.1 mg/L BA, however, the highest production of callus was observed on medium with 2,4-D/2iP.

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Rongcai Yuan and Duane W. Greene

BA applied at the 10-mm stage at 50 and 100 ppm thinned, increased fruit size, and seed abortion. Net photosynthesis was decreased and dark respiration was increased when temperature following BA application was high (30°C), whereas there was no effect when temperature was lower (20°C). The seed number in abscising fruit was greater in BA-treated fruit than in control fruit. The number of viable seeds in BA-treated fruit was reduced. Tipping the bourse shoot increased fruit set, regardless of BA treatment. BA did not thin fruit with 25 leaves or greater. The translocation of 14C-sorbital from leaves to fruit was promoted by BA application to the fruit, but not when BA was applied to the leaves. The thinning induced by BA will be discussed in relation to available carbohydrate.

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M.R. Pooler and R. Scorza

Shoots were regenerated from cotyledons of mature stored seed of three peach rootstock cultivars (`Flordaguard', `Nemared', and `Medaguard'). Shoot regeneration rates were highest when cotyledons were cultured for 3 weeks in darkness on Murashige and Skoog (MS) medium with 2.5% sucrose and a combination of IBA (1.25 or 2.5 μm) and TDZ (6.25 or 12.5 μm). Regeneration rates for `Flordaguard', `Nemared', and `Nemaguard' were as high as 60%, 33%, and 6%, respectively. Length of seed storage (1 to 3 years) did not affect regeneration rates. Seventy percent of regenerated shoots produced rooted plants. This regeneration method is rapid and simple, and stored seed can be used year-round. It may be a useful regeneration system for gene transfer in seed-propagated peach rootstocks. Chemical names used: 5 indole-3-butyric acid (IBA); thidiazuron (TDZ).

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James A. Bryan and John R. Seiler

Foliar application of the synthetic growth regulator BA was evaluated for increasing the duration and extent of Fraser fir [Abies fraseri (Pursh.) Poir.] seedling growth. Aqueous solutions of 0, 222, or 444 μm BA (0, 50, or 100 ppm) were sprayed on the shoots of Fraser fir seedlings biweekly from 18 until 38 weeks after planting. Foliar sprays of 444 μm BA increased seedling height 19%, increased shoot weight 57%, reduced root weight 22%, and increased total weight 27%. Apical meristem activity was stimulated and the long periods of dormancy typical of Fraser fir seedlings were avoided. Chemical name used: 6-benzylaminopurine (BA).

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Dale T. Lindgren and Brent McCown

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Don C. Elfving and Dwayne B. Visser

A new bioregulator, cyclanilide (CYC, Bayer Environmental Science, Montvale, N.J.), was tested for growth-related effects on apple trees over three years. Although treatment with CYC produced small reductions in shoot length, its principal effect was to stimulate the formation of lateral shoots on current-season's shoot growth and from spurs on older wood. CYC treatment of `Scarletspur Delicious' apple trees in the nursery more than doubled the formation of well-developed feathers with wide crotch angles (≈60°) and with no effect on final tree height. CYC appeared to flatten the apples and reduce fruit size in one trial. CYC appears promising for lateral branch induction in apple, especially in the nursery. Chemical names used: 1-(2,4-dichlorophenylaminocarbonyl)-cyclopropane carboxylic acid (Cyclanilide); calcium 3-oxido-4-propionyl-5-oxo-4-propionylcyclohex-3-enecarboxylate (prohexadione-Ca, Apogee); N-(phenylmethyl)-1H-purine-6-amine + gibberellins A4A7 (Promalin); polyoxyethylenepolypropoxypropanol, dihydroxypropane, 2-butoxyethanol (Regulaid).

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James O. Denney and George C. Martin

Fruit removal force (FRF) and percent leaf drop (LD) of fruit-bearing olive (Olea europaea L.) shoots were examined 120 hours after being sprayed with ethephon at 600 mg·liter-1 and held under controlled-environmental conditions analogous to those found in the field in California at harvest time in mid-October. FRF was not significantly affected by solution pH, but FRF of all treated shoots was significantly lower than that of the untreated controls. Only at pH 5 was percent LD significantly greater than that of the controls, but, of the shoots treated with ethephon, the lowest percent LD occurred at pH 3. Percent LD after treatment with ethephon at pH 3 was not affected by application time, but FRF was significantly less than the controls' when shoots were treated at 7 am or 12 pm but not at 5 pm or 10 pm. Adding NAA to the ethephon solution raised FRF and adding BA lowered FRF compared to ethephon alone. Adding NAA or BA did not mitigate percent LD significantly. Adding BA advanced anthocyanin production in fruit. Ethephon penetration of rachides was ≈70% that of petioles. Correlation between ethephon penetration of petioles and percent LD was greater than that between penetration of rachides and FRF. Correlation was significant for both tissues only in the 12 pm pH 3 treatment; correlation was also significant for petiole penetration and percent LD at pH 5. Autoradiographic studies of the 14C-ethephon penetration showed no pH effect, greater penetration into petioles than rachides, and that radioactivity was limited largely to intercellular spaces, with accumulation in vascular bundles, especially xylem. Regardless of treatment, FRF and percent LD are negatively correlated (r 2 = 0.615). Mean results to be expected using ethephon as an olive harvest aid under these conditions are an FRF of ≈3 N and a percent LD of ≈15%. The desired low FRF and percent LD were obtained by applying ethephon alone at pH 3 at 7 am. Raising ethephon solution pH does not increase harvest effectiveness. Chemical names used: (2-chloroethyl)phosphonic acid (ethephon), naphthalene acetic acid (NAA), 6-benzylaminopurine (BA).

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Diane M. Camberato, James J. Camberato and Roberto G. Lopez

), benzyladenine (BA), chlormequat chloride (CC), daminozide (DZ), dikegulac-sodium (DS), ethephon (EP), flurprimidol (FP), gibberellic acid (GA), gibberellic acid/benzyladenine (GA/BA), paclobutrazol (PB), and uniconazole (UC) ( Table 1 ) on final solution pH was

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Martín Mata-Rosas and Víctor M. Salazar-Rojas

shoot formation. ( A ) Flowering plant. ( B ) Multiple shoot formation from protocorms in Murashige and Skoog medium + 13.3 μM N 6 -benzyladenine. ( C ) In vitro-rooted shoots ready for ex vitro culture. ( D ) Plants obtained from in vitro culture after

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Takahiro Tezuka, Masashi Harada, Masahumi Johkan, Satoshi Yamasaki, Hideyuki Tanaka and Masayuki Oda

PGRs 1-naphthaleneacetic acid (NAA) and 6-benzyladenine (BA), which are commonly used in tissue culture, were applied to decapitated plants as foliar sprays to understand the physiology of shoot regeneration by CDM and to improve the efficiency of shoot