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

balance in developing shoots, with red and blue light altering endogenous auxin and gibberellins ( Baraldi et al., 1995 ). We hypothesized that light quality may alter responses of apple rootstocks to exogenous GA 3 . The purpose of this study was to test

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

, M.A. Brick, R.M. Harveson, and G.D. Franc (eds.). Dry bean production & integrated pest management, 2nd ed. Colorado State Univ. Reg. Bul. 562A Takahashi N. Phinney B.O. MacMillan J. 1991 Gibberellins. Springer-Verlag, New York, NY

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Donglin Zhang, Diemeng Hu, and John Smagula

Iris versicolor (blue-flag iris) is a native aquatic plant that grows from Maine to Virginia. It is an important species of wetland regeneration and restoration. Unfortunately, seed germination seldom occurs in the wild. To address this problem, seeds of Iris versicolor were soaked with gibberellin acid (0, 500, 1000, and 1500 ppm) for 24 h after 120 days of cold treatment at 4 °C and then were randomly assigned to three germination temperatures (constant 21 °C; 24 °C/18 °C; 27C/15 °C) and placed in darkness. Germination rates for the three temperature treatments were 54.4% (21 °C), 96.5% (24 °C/18 °C), and 96.0% (27C/15 °C). Oscillating temperature treatments had significantly greater germination rate than constant temperature. Gibberellin acid had significant influence on germination rate; only the constant 21 °C was not favorable for germination. The germination rate was higher at 1000 than at 500 ppm or 1500 ppm or more. Germination occurred within 10 days under germination temperature treatments. All seedlings in petri dishes were successfully transplanted into growing flats.

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Mauricio J. Sarmiento and Jeff S. Kuehny

Rhizomes of Curcuma alismatifolia Roxb. `Chiang Mai Pink', C. gracillima Roxb. `Violet', and C. thorelii Roxb. were soaked in gibberellin (GA4+7) at 0, 200, 400, or 600 mg·L-1 (ppm) and planted into 15.2-cm-diameter (6 inches) containers. The plants were grown in a greenhouse at 30 °C day/23 °C night (86.0/73.4 °F) temperatures. When shoot height was 10 cm (3.9 inches), the plants were drenched with 118 mL (3.9 fl oz) of paclobutrazol at 0, 2, 3, or 4 mg a.i. per 15.2-cm-diameter container. Gibberellin4+7 delayed shoot emergence and fl owering but did not affect the fl ower number. Paclobutrazol rates were not effective in controlling height of C. alismatifolia `Chiang Mai Pink' averaging 85 cm (33.5 inches), C. gracillima `Violet' averaging 25 cm (9.8 inches), or C. thorelii averaging 17 cm (6.7 inches). Curcuma alismatifolia `Chiang Mai Pink', C. gracillima `Violet', and C. thorelii had postproduction longevities of 4.6, 2.6 and 3.8 weeks respectively, making these three species of curcuma excellent candidates for use as fl owering pot plants.

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Alan R. Langille and P.R. Hepler

Non-induced Katahdin potato plants were treated with three anti-gibberellins: CCC, BAS-106 and BAS-111. Other plants were sprayed with GA3 and placed in an inducing chamber. All treatments were repeated the following week. After final treatment, apical, sub-apical, medial and basal leaf bud-cuttings were taken from each plant and placed 1n a mist chamber. After two weeks, cuttings were examined for tuberization. BAS-111 and CCC were associated with 3.5 and 2 fold increase, respectively, in tuberization of cuttings over the non-induced control. Although induced control cuttings exhibited 100% tuberization, application of GA to plants grown under identical conditions, reduced tuberization 20 fold. In non-induced control cuttings and those treated with CCC, basal cuttings tuberized significantly better than those taken from higher on the stem. This pattern was reversed for plants treated with BAS-111. These results will be discussed in light of current understanding of the tuberization phenomenon.

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Mariken Rebers, Evert Vermeer, Erik Knegt, and Linus H.W. van der Plas

To find a suitable indicator for properly cold-treated tulip bulbs (Tulipa gesneriana L. cv. Apeldoorn), the content of the endogenous free gibberellins (GAs) GA1, GA4, GA9, GA24, and GA34 was investigated. GA levels were measured in the shoots and basal plates at the start and at the end of a complete cold treatment of 12 weeks at 5 °C by combined gas chromatography–mass spectrometry using deuterated internal standards. Bulbs stored at 17 °C for 12 weeks served as controls and the experiment was repeated three times. Before the cold treatment, GA1 and GA4 were the major occurring GAs in the shoots. After 12 weeks, GA4 was the main GA component and the levels of GA1 were low in precooled and nonprecooled bulb shoots. The levels of GA4, GA9, GA24, and GA34 in precooled and nonprecooled bulb shoots and basal plates were similar. Hence, no direct correlation between cold-stimulated growth and a change in the endogenous GA status in shoots or basal plates was determined during the cold treatment. The free GA content in shoots or basal plates at the end of bulb storage cannot be used as a marker in a test for properly cold-treated `Apeldoorn' tulip bulbs.

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Kathryn Keeley, John E. Preece, and Bradley H. Taylor

Hardwood and softwood cuttings of Vitis aestivalis Michx. 'Norton' were rooted under intermittent mist in a series of experiments using cuttings collected from two local vineyards. Hardwood cuttings treated in late March responded in a similar manner to KIBA and KNAA. Although there was little increase in the percentage rooting above 22.29 mm KIBA or 20.72 mm KNAA (5000 mg·L-1 of either auxin), root number (but not root length) increased linearly on cuttings treated with up to 44.58 mm KIBA or 41.44 mm KNAA (10000 mg·L-1 auxin). Cuttings treated with 10000 mg·L-1 auxin produced up to 4 times more roots than the nontreated controls. The gibberellin biosynthesis inhibitors CCC and PAC had little effect on either hardwood cuttings or softwood cuttings that were harvested, treated and placed in the propagation bench in June. However, when softwood cuttings were collected in August, the most roots were found on cuttings treated with 50.6 mm CCC or 0.85 μm PAC. Although all hardwood cuttings were collected at the same time and stored under refrigerated conditions, rooting percentage increased as storage time increased, especially on the nontreated control cuttings. When the cuttings were stored for the longest time (six weeks), KIBA no longer caused more roots per cutting. Chemical names used: potassium salt of indole-3-butyric acid (KIBA), potassium salt of α-naphthaleneacetic acid (KNAA), chlormequat chloride (CCC), paclobutrazol (PAC).

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Moritz Knoche and Martin J. Bukovac

Gibberellin A3 (GA) applied to virus-infected sour cherry (Prunus cerasus L., `Montmorency') trees inhibits flower initiation and promotes spur formation. However, response to a given dose may vary. Differential foliar absorption has been suggested as a major source of this variation. Therefore, we studied if surfactants would reduce variation in GA absorption. Uptake through the abaxial surface exceeded that through the adaxial surface by about one order of magnitude (adaxial surface 1.1 vs 7.8% in 1988, 0.7 vs 16.6% in 1989). GA uptake was markedly affected by surfactants. Over a 24-hr uptake period, Activator 90 and Ortho X-77 were most effective (abaxial surface 38.3 and 37.4% in 1989), whereas Regulaid did not affect GA uptake. L-77 significantly depressed absorption (abaxial surface 9.1% in 1989). In addition to the level of uptake, surfactants also changed GA absorption kinetics. Penetration increased linearly over a 96-hr time period when Regulaid was included. However, with Ortho X-77, uptake was rapid initially but levelled off within 96 hr. These findings will be discussed in relation to biological response data obtained in the field experiments.

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Yicheng Tu, Peter Hirst, Ronald Coolbaugh, and Richard Pharis

It is believed that gibberellins (GA) produced in apple seeds act as an inhibitory signal to flower induction in the neighboring buds. The alternate bearing behavior of an apple cultivar is therefore likely to be associated with the activity of endogenous GAs in the seeds of that cultivar. To elucidate the impact of GAs on the flowering of biennial and non-biennial apple cultivars, fruits were sampled from `Fuji' (biennial, on-year) and `Gala' (non-biennial) trees periodically during the early part of the growing season. Seeds were removed from fruits immediately, frozen in liquid Nitrogen and freeze dried. Full scan analysis for GAs using GC-MS identified 16 GAs: GA1, GA3, GA4, GA7, GA20, GA31, GA34, GA35, GA44, GA50, GA54, GA61, GA63, GA68, GA80, and GA88. In addition, we also traced a number of GA-like mass spectra that do not match any published GA mass spectrum reference. The possible structures of these GA-like compounds were also proposed. More types of GAs were found in `Fuji' seeds than in those of `Gala'. This suggests higher GA activity in `Fuji' considering almost all the GAs identified are biologically active. Unlike the results of recent researches on GAs in other apple cultivars, we found that the major GA types in both cultivars are GA80 and GA63, rather than GA4 and GA7. `Fuji' contained significant amounts of GA88, which did not appear in `Gala' samples. Other studies are currently underway to quantify specific GAs from these seeds using deuterated internal standards.

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Grete Grindal Patil, Vibeke Alm, Roar Moe, and Olavi Junttila

The role of phytochrome in control of stem elongation by daily temperature alternations is unclear. The aim of this work was to study the involvement of phytochrome B in thermoperiodism in cucumber (Cucumis sativus L.), and the interaction with gibberellin (GA). The wild type and the phytochrome B deficient, long-hypocotyl (lh) cucumber mutant were grown under alternating day (DT) and night temperature (NT) and either with or without an exposure to end-of-day far-red light (EOD-FR). Without EOD-FR, hypocotyl and internodes of the wild type plants were shorter under a low DT (19 °C)/high NT (25 °C) (negative DIF) compared with a high DT/low NT regime (positive DIF), while the number of leaves was reduced by 12%. EOD-FR enhanced elongation of hypocotyl and internodes. However, EOD-FR reduced the effect of alternating temperature on hypocotyl elongation. The lh cucumber mutant did not respond to EOD-FR treatments, but internode length was slightly increased by positive compared with negative DIF. The results suggest that phytochrome B is required for a maximum effect of daily temperature alternations on stem elongation in cucumber. Additional GA4 reduced the difference between positive and negative DIF, but it had a minor effect only on the difference between EOD-FR and EOD red light (EOD-R) in the wild type. Plants depleted for endogenous GA by the GA biosynthesis inhibitor paclobutrazol, did not respond at all to DIF or EOD treatments. When seedlings were treated with prohexadione-calcium, which blocks both biosynthesis and inactivation of GA4, response to applied GA4 was enhanced by EOD-FR. The present results suggest that, in cucumber, EOD-FR, and probably also positive DIF, enhances tissue sensitivity to GA4. In addition, catabolism of GA4 can be enhanced by negative DIF.