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Y. Manakasem and P.B. Goodwin

Field surveys were conducted on cultivated strawberries (Fragaria ×ananassa Duch.) to determine the time of flower initiation and its relation to maximum and minimum temperatures and daylength. Stereomicroscopy and scanning electron microscopy (SEM) were compared. Flower initiation in `Torrey' strawberry was more dependent on minimum temperature than on daylength or maximum temperature. Flower initiation in the day-neutral `Aptos' occurred regardless of daylength or temperature during sampling. For the study of flower initiation and inflorescence development, SEM gave more detail than stereomicroscopy.

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Brian P. Pellerin, Deborah Buszard, Alex Georgallas, and Richard J. Nowakowski

, spring frost, diseases, light interception, and canopy architecture manipulation can also impact the bearing pattern of apple trees ( Davis, 2002 ; Fulford, 1965 ; Willaume et al., 2004 ). High crop yields inhibit flower initiation. Chan and Cain (1967

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James R. Schupp, Thomas M. Kon, and H. Edwin Winzeler

The objective of these studies was to evaluate the efficacy of several concentrations of 1-aminocyclopropane carboxylic acid (ACC) for thinning apple at the standard growth stage for chemical thinning timing and a late thinning growth stage. ACC was applied at concentrations of 0, 100, 300, or 500 mg·L−1 to ‘Golden Delicious’/Bud.9 apple trees at 10 mm or 20 mm fruit diameter. Treatments were applied to the point of drip to individual whole trees in a completely randomized design with five (2010) and six (2011) replications. When ACC was applied at 20 mm, there was a linear dose relationship between concentration and fruit thinning in both years. ACC was ineffective at 10 mm. The naturally occurring compound ACC shows potential for use as a reliable late chemical thinner for apple.

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Ryan M. Warner and John. E. Erwin

Flowering of many herbaceous ornamentals is reduced or eliminated under high temperatures. On warm, sunny days, greenhouse growers often cover crops with light-reducing screening materials to reduce air and plant temperature. However, low irradiance can also reduce flowering on many species. To examine the impacts of temperature and irradiance on herbaceous ornamental flowering and to select a model to study high temperature-reduced flowering, Antirrhinum majus L. (snapdragon) `Rocket Rose', Calendula officinalis L. (calendula) `Calypso Orange', Impatiens wallerana Hook.f. (impatiens) `Super Elfin White', Mimulus ×hybridus Hort. ex Siebert & Voss (mimulus) `Mystic Yellow', and Torenia fournieri Linden ex E. Fourn (torenia) `Clown Burgundy' were grown at constant 32 ± 1 °C or 20 ± 1.5 °C under a 16-hour photoperiod with daily light integrals (DLI) of 10.5, 17.5, or 21.8 mol·m-2·d-1. Flower bud number per plant (all flower buds ≥1 mm in length when the first flower opened) of all species was lower at 32 than 20 °C. Reduction in flower bud number per plant at 32 compared to 20 °C varied from 30% (impatiens) to 95% (torenia) under a DLI of 10.5 mol·m-2·d-1. Flower diameter of all species except snapdragon was less at 32 than 20 °C. Decreasing DLI from 21.8 to 10.5 mol·m-2·d-1 decreased flower diameter of all species except snapdragon. Calendula, impatiens, and torenia leaf number below the first flower was greater at 32 than 20 °C, regardless of DLI. Increasing DLI from 10.5 to 17.5 mol·m-2·d-1 increased shoot dry mass gain rate of all species, regardless of temperature. Further increasing DLI from 17.5 to 21.8 mol·m-2·d-1 at 20 °C increased shoot dry mass gain rate of all species except snapdragon and mimulus, indicating that these species may be light saturated below 21.8 mol·m-2·d-1. Under DLIs of 17.5 and 21.8 mol·m-2·d-1 shoot dry mass gain rate was lower at 32 than 20 °C for all species except torenia. Torenia shoot dry mass gain rate was 129 mg·d-1 at 20 °C compared to 252 mg·d-1 at 32 °C under a DLI of 17.5 mol·m-2·d-1. We suggest torenia may be a good model to study the basis for inhibition of flowering under high temperatures as flowering, but not dry mass gain, was reduced at 32 °C.

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Martin Makgose Maboko and Christian Phillipus Du Plooy

reduced preharvest fruit drop with increased number of fruits per plant and increased yield as a result of the application of NAA or β-NAA spray. Repeated application of 27 mg·L −1 NAA at the beginning of flower initiation significantly increased

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Lisa Wasko DeVetter, Rebecca Harbut, and Jed Colquhoun

) evaluate flower initiation, bud development, and potential return bloom across cultivars; and 2) determine the relationship between external appearance of buds and the presence/absence of flower initials. Information on these characteristics will be

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Duane W. Greene, James R. Schupp, and H. Edwin Winzeler

Experiments were conducted over a 5-year period to determine the effects of abscisic acid (ABA) and benzyladenine (BA) applied alone and in combination on fruit set, fruit quality, and return bloom of ‘McIntosh’ and ‘Fuji’ apples. ABA thinned in 3 of the 5 years used and it thinned ‘McIntosh’ when applied at bloom, petal fall, and at the 10-mm fruit size stage. On ‘Fuji’, ABA thinned over a range of concentrations from 150 to 1000 mg·L−1. It caused leaf yellowing on ‘McIntosh’ but not on ‘Fuji’. When BA was applied with ABA on ‘McIntosh’, even at a rate as high as 1000 mg·L−1, it either dramatically reduced or prevented leaf yellowing and leaf abscission. The usefulness of applying BA with ABA was inconclusive because of variability in thinning response. ABA advanced surface red color on ‘McIntosh’ and when combined with BA, it reversed the reduction in red color caused by BA.

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Audrey I. Gerber, Karen I. Theron, and Gerard Jacobs

Protea L. sp. can be assigned to groups according to similar times of flower initiation and harvest. The stages occurring during flower initiation and their synchrony relative to shoot growth were investigated for three cultivars when flower initiation occurred on the spring growth flush. For all three cultivars, the spring flush was preformed and enclosed in the apical bud before spring budbreak. During elongation of the spring flush, the apical meristem produced floral primordia which differentiated into involucral bracts. After completion of the spring flush, meristematic activity continued and produced floral bracts with florets in their axils. The different cultivars were characterized by differences or similarities in the time of budbreak, and the rates of shoot growth, appendage formation, and flower development. Insight into the time of flower initiation relative to vegetative growth could be useful in making management decisions, as well as forming a basis for manipulation of the flowering process.

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Saquib Waheed, Yuan Peng, and Lihui Zeng

has higher activity under SD conditions, suggesting that DlGI may play a role in responding to SD conditions and inducing flower initiation in longan. Variation in GUS activity under different photoperiods indicates that the conserved motif

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Steven Dupee Dr. and Peter Goodwin

The strategy of this study was to determine the period of floral initiation for both species and then to determine the critical regulator(s) of flower initiation and floral development. Plants grown under different temperature regimes gave best shoot extension and flower initiation at temperatures with 10°C night and 15 to 25°C day. Field data from four locations showed a correlation of time of flower initiation and temperatures over the same range.

Temperature is an important determinant of the vegetative flush period of both species. The stem diameter of all shoots is a consequence of the vegetative flush growth and in turn is well correlated with flower initiation. Plants given day temperatures of 20°C or above remain in the vegetative phase. Flower abortions in Protea neriifolia and reversions from floral to vegetative shoots in Protea cynaroidesresult from high day temperatures.

Daylength was not found to be critical for flower initiation. A cool temperature period acts as a control to change shoots from the vegetative to reproductive phase.