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Berardo Escalante and Alan R. Langile

Foliage of non-induced `Katahdin' potato plants was treated with BAS-111. Other plants were sprayed with GA3 solution and placed in an inducing chamber. All treatments were repeated the following week. After final treatment, apical, sub-apical, medial, and basal nodal stem segments were taken from each plant, surface-sterilized, and placed on MS culture media. After 3 weeks in a darkened incubator, cultures were examined. Induced plants produced 5.5 times more tubers than did non-induced segments. BAS-111 applied to non-induced plants was associated with 63% reduction in rhizome length and 3.2-fold increase in tuber number. GA treatment to induce plants resulted in improved rhizome elongation, delayed and reduced tuberization when compared with control explants. Lower nodes produced more and larger tubers than did younger tissues. Results will be discussed in light of current literature.

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Wallace G. Pill and Elizabeth A. Kilian

`Moss Curled' seeds of parsley (Petroselinum crispum L.) were primed osmotically in polyethylene glycol or matrically in fine, exfoliated vermiculite at -0.5 MPa for 4 or 7 days at 20 or 30 °C with 0 or 1 mm GA3. All priming treatments stimulated and hastened germination. Matric priming resulted in greater germination (89%) than osmotic priming (83%) when seeds were primed for 7 days at 30 °C, but priming agent had no effect on germination percentage following priming at 20 °C or for 4 days. In seeds primed for 4 days at 20 or 30 °C, matric priming hastened germination more than did osmotic priming. Germination was generally less synchronous with matric than with osmotic priming. Increasing priming time from 4 to 7 days increased the rate of germination, but increased germination synchrony only when seeds were primed a t 20 °C. Inclusion of 1 mm GA3 during priming had little or no effect on germination. All matric priming treatments (other than 4-day priming) were repeated to assess seedling emergence in a greenhouse (25°C day/22 °C night). Priming increased the percentage, rate and synchrony of emergence, and increased hypocotyl length at 3 weeks after planting. Priming at 30 °C with 1 mm GA3 resulted in the greatest emergence percentage, hypocotyl length, and shoot dry weight. We conclude that matric priming is a satisfactory alternative to osmotic priming of parsley seeds. Chemical name used: gibberellic acid (GA3).

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Moo R. Huh, Beyoung H. Kwack, and Leonard P. Perry

Shoot length, leaf length and width, root length, and crown diameter were affected by 0.0-, 0.5-, 1.0-, and 5.0-mg·liter–1 uniconazole drench and 25- or 50-mg·liter–1 GA3 spray but not significantly by 0.0%, 2.5%, and 5.0% NaCl. Leaf width of H. syriacus Sieb. & Zucc. was not affected and that of H. syriacus L. significantly decreased, as NaCl concentration increased. Effect of NaCl on H. syriacus leaf width was offset by treatment with uniconazole but not by GA3 treatment. With 2.5% NaCl, dry weight of H. hamabo treated with uniconazole or GA3 increased and that of treated H. syriacus decreased. With 5.0% NaCl, dry weight of both species decreased with uniconazole or GA3. Calcium at 13.35 or 133.5 mM decreased the reduction of dry weight by NaCl treatment. The dry: fresh weight ratio of H. hamabo and H. syriacus treated with NaCl plus uniconazole was higher than that only treated with NaCl. GA3 treatment with NaCl did not affect the dry: fresh weight ratio for either species

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Will G. Neily, Peter R. Hicklenton, and David N. Kristie

Experiments were conducted to determine the effects of treatment with gibberellic acid (GA) on changes in diurnal growth rhythms caused by maturation and day/night temperature differential (DIF) in zinnia (Zinnia elegans Jacq. `Pompon'). Plants were treated with GA3 or with the GA biosynthesis inhibitor daminozide under three DIF regimes (+5 DIF: 21 °C DT/16 °C NT; 0 DIF: 18.7 °C constant; –5 DIF: 16.5 °C DT/21.5 °C NT), each with a daily average temperature of 18.7 °C, at two developmental stages: stage 1, the period of vegetative growth before flower bud formation; and stage 3, growth just before anthesis. Instantaneous stem elongation rates (SER) were measured using linear voltage displacement transducers. The DIF regime, as has been previously shown, influenced stem elongation primarily by altering the size of an early morning peak in SER; peak height increased as DIF became more positive. GA3 increased SER throughout the diurnal period with a proportionately larger effect on nighttime growth. Conversely, daminozide decreased SER more or less equally throughout the diurnal period. Neither GA3 or daminozide transformed growth patterns to match those of positive or negative DIF plants, but instead simply increased or decreased growth amplitude. Furthermore, neither growth regulator altered the basic diurnal SER pattern at any DIF, or influenced the observed shift to greater nighttime growth as plants matured from stage 1 to stage 3. The results suggest that neither the effects of DIF, or the age-related shift in diurnal growth distribution can be explained by changes in total availability of GA in the plant. Chemical name used: mono (2,2-dimethylhydrazide) butanedioic acid (daminozide).

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Henry R. Owen and Louis H. Aung

A relationship between ovary size at anthesis and final fruit diameter of 12 tomato (Lycopersicon esculentum Mill.) cultivars with a range of fruit sizes, shapes, and maturation rates was determined. `Fireball', `Michigan/Ohio Hybrid', and `New Yorker' produced nonfasciated, spherical fruits of intermediate maturation rate and showed a significantly higher correlation between ovary diameter at anthesis and final fruit diameter than `Small Fry', `Roma VF', `Early Cascade', `Campbell 1327', or `Ponderosa'. A linear regression of final fruit diameter at maturity on ovary diameter at anthesis of the cultivars was highly significant (r2 = 0.92**; ÿ = 22.5X - 0.3). Continuous root application of 0.01 μm BA to seedlings of `Fireball' significantly delayed anthesis. A single foliar application of 0.37 mM NOA to `Fireball' plants at the appearance of the first inflorescence significantly increased ovary diameter on the first inflorescence, but decreased ovary diameter on the second inflorescence. Treatment with NOA altered final fruit shape but not final fruit diameter. Single foliar applications of 0.1 mM GA stimulated stem and peduncle elongation but did not affect fruit size. Chemical names used: ß-naphthoxyacetic acid (NOA), N6-benzylaminopurine (BA), gibberellic acid, (GA).

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Fang Geng, Renae Moran, Michael Day, William Halteman, and Donglin Zhang

These studies were conducted to determine the most effective methods for increasing shoot elongation during the initial proliferation stage of micropropagation in two dwarfing apple, Malus ×domestica (Borkh.), rootstock cultivars. Several experiments were conducted to compare explant collection date, exposure to chilling (5 ± 1 °C) temperatures, and varying concentrations of plant growth regulators in Murashige and Skoog (MS) media. Microshoot growth of ‘Geneva 41’ (‘G.41’) was very low and unaffected by chilling duration from 0 to 8 weeks or by gibberellic acid (GA3) concentration from 0 to 1.0 mg·L−1, but was improved by an additional subculture which increased shoot length from 1 to 15 mm. In ‘Geneva 30’ (‘G.30’), shoot elongation was most affected by date, chilling explants, and by optimizing cytokinin concentration and type. Explant collection date in April increased shoot growth compared with August or November. Microshoot growth of ‘G.30’ was increased by chilling nodal explants for 4 and 6 weeks when explants were collected in August and November, but not in April. Eight weeks chilling was detrimental for explants collected in April, and generally had little or no effect with August and November. The cytokinin 6-benzylaminopurine (BA) increased shoot number to a greater extent than thidiazuron (TDZ) or zeatin (ZT), and was also more effective for increasing shoot elongation with concentrations of 0 to 2.0 mg·L−1. In ‘G.30’, GA3 increased shoot growth at the optimum concentration of BA, but not with lower concentrations. ‘G.30’ microshoots were fewer and shorter with 24-epi-brassinolide (EBR) at concentrations of 0.1 and 1.0 mg·L−1. Chemical names: N-phenyl-N’-(1,2,3-thiadiazol-5-yl)urea (TDZ), 6-(4-hydroxy-3-methylbut-2-enylamino)purine (ZT).

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I. Baktir, S. Ulger, L. Kaynak, and David G. Himelrick

Changes in hormone concentrations in leaf, node, shoot tip, and fruit samples of three Turkish olive (Olea europaea L.) cultivars (`Gemlik', `Memecik', and `Tavsan Yuregi') were monitored at monthly intervals over two successive years of the alternate-bearing cycle. Concentrations of abscisic acid (ABA), indole acetic acid (IAA), gibberellic acid-like substances (GA), and kinetin-like cytokinin were determined and their relationship to flower bud formation were examined during “on” and “off” years. Results showed significant differences in IAA, ABA, GA3-like, and kinetin-like cytokinins between “on” and “off” cropping years in various tissues of olive trees. Relative balances between GA3-like and ABA concentrations of tissues appears to exhibit evidence of being a key regulator of floral development and alternate bearing.

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Smit le Roux and Graham H. Barry

As part of a larger study to improve rind color of citrus fruit, this initial study was conducted to determine the concentration of various gibberellin-biosynthesis inhibitors required to elicit a biological response in citrus trees as measured by

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Jennifer Han, Jan E. Murray, Qingyi Yu, Paul H. Moore, and Ray Ming

spherical fruit produced by females ( Higgins and Holt, 1914 ). Plant hormones play diverse roles in growth and development with most having pleiotropic effects. Gibberellin is a major phytohormone that functions to not only promote normal growth and