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Christine Yung-Ting Yen, Terri W. Starman, Yin-Tung Wang, Andreas Holzenburg, and Genhua Niu

already induced but not yet differentiated. Therefore, to investigate flower differentiation, axillary buds were sampled only after they had protruded 2 mm from the pseudobulb epidermis. Fig. 3. Longitudinal sections of vegetative apex and

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K. Yonemori, A. Sugiura, K. Tanaka, and K. Kameda

Patterns of floral differentiation were studied in two monoecious-type Japanese persimmon (Diospyros kaki L.) cultivars Hana-gosho and Kakiyama-gaki. In both cultivars, the pistillate and staminate floral primordium started to differentiate in early June, and differentiation progressed until August, when the sepal primordia in pistillate flowers and petal primordia of staminate flowers had become evident. The buds then entered a quiescent, overwintering state. Thus, flower sex of monoecious-type persimmons was determined at a relatively early stage of floral development. Moreover, in both cultivars, sex differentiation was associated with previous history of the current season's shoots. Current season's shoots that bore pistillate flowers differentiated pistillate buds (mixed buds from which pistillate flowers emerge) at significantly higher rates than for shoots that bore staminate flowers. Similarly, shoots that bore staminate flowers produced staminate buds (mixed buds from which staminate flowers emerge) at a higher percentage than shoots that had borne pistillate flowers. With `Hana-gosho', the flower type was also predictable with fair accuracy by bud position on the current season's shoot, i.e., pistillate flowers emerged from distal mixed buds, whereas staminate flowers arose predominantly from basal buds.

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J.H.M. Barten, J.W. Scott, N. Kedar, and Y. Elkind

To identify the stage of flower development sensitive to low temperature-induced rough blossom-end scarring (RBS) in tomato (Lycopersicon esculentum Mill.), short-term low-temperature treatments (1, 3, and 5 days continuously at 10C or 6, 9, and 12 days at 18/10C day/night) were applied to young, flowering plants and to plants at the six-leaf stage. Flowers were tagged at anthesis over 4 weeks and the growth stage of the flowers at the beginning of the treatments was determined in days relative to anthesis. The blossom-end scar index (BSI), a measure for blossom-end scar size relative to fruit size, and number of locules were recorded for mature fruits. In three experiments, 5 days at 10C or 6 days at 18/10C, applied during early flower differentiation, induced RBS in mature fruits. For each of the three cultivars tested `Horizon', Waker', and `Solar Set'), flower buds were most sensitive from 26 to 19 days before anthesis. In this experiment, RBS induction was not caused by an increase in the average number of locules per fruit. A short period of sensitivity during very early flower development explains the variation in RBS among seasons and within plants encountered in field situations. This study also presents a standard induction technique for further investigation of physiological and morphological backgrounds of the disorder and possible genotype screening.

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Jose Lopez-Medina and James N. Moore

Root cuttings of A-1836, APF-13, and NC194 primocane-fruiting (PF) blackberry (Rubus subgenus Rubus) genotypes were dug from the field on 31 July 1997 and stored in plastic bags at 2 °C for 32 days. On 1 Sept. freshly dug root cuttings, along with the cold-treated ones, were planted in pots, which were kept in a lath house for 4 weeks and then moved to a heated greenhouse under natural daylength. Cold-treatment hastened emergence of all genotypes. Transition from vegetative to floral phase was first observed in cold-treated A-1836 and APF-13 at the fifth node, with floral appendages clearly evident in both genotypes at the seventh node 45 days after planting (DAP). Bloom started on 26 Nov. and 5 Dec. 1997 and the first fruits were picked on 10 and 25 Jan. 1998 in cold-treated APF-13 and A-1836, respectively. Plants of cold-treated NC194 and of all non-cold-treated genotypes remained stunted with rosetted leaves, showing no signs of floral initiation until 150 DAP. These findings show that exposure to chilling prior to shoot emergence greatly promotes flowering in PF blackberries, and may have application in greenhouse culture of blackberry.

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Ying Gao, Hao Liu, and Dong Pei

transport contributes to the independent regulation of preanthesis filament elongation; hence, auxin is an important physiological regulator of staminate flower differentiation. Using immunologic techniques, auxin can be detected in situ in plant tissues

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Yi-Lu Jiang, Yuan-Yin Liao, Tzong-Shyan Lin, Ching-Lung Lee, Chung-Ruey Yen, and Wen-Ju Yang

a long day is required for further flower differentiation ( Fig. 3A ). Daylength extension or night-breaking may regulate the vegetative and reproductive growth of cactus plants ( Boyle, 1991 ; Gutterman, 1995 ). Yen and Chang (1997) reported the

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Adriana Beatriz Sanchez-Urdaneta, Raquel Cano-Medrano, and Jorge Rodrl̀guez-Alcazar

The purpose of this research was to investigate the effect of 1% N foliar sprays (0, 2, and 4 sprays at weekly intervals) and girdling (G) on budbreak of three peach advanced selections CP95-1 °C, CP91-8, and CP91-17, and its relationship with both reduced nitrogen (RN) and polyamine contents. Foliar N was applied in July, before flower initiation was detected and girdling was performed 30 days after nitrogen sprays (DAT) The results indicate that 4N+G treatment had the highest content of (RN) with values between 232 and 1000 mg N/g of DW. CP 91-17 and CP95-1 °C selections showed higher RN content than that of CP91-8. Both 2N+G and 4 N+G showed the highest content of putrescine (Put) (908 and 1635 nmol·g-1 FW, respectively). Among peach selections CP91-8 was the one with the highest content of Put. Putrescine content went down as the flower differentiation process evolved. Four N+G treatment promoted budbreak in CP95-1 °C advancing it in 55 days as compared to the control. Budbreak began earlier in the three peach selections treated with 4N+G (11/12/98) followed by 2N+G treatment (7/001/99), and the control (4/02/99). Fruit set was 19%, 12%, and 11% for 4N+G, 2N+G, and control treatments, respectively.

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Peter M. Hirst and Wendy M. Cashmore

Spurs were collected periodically throughout three growing seasons from the 1-year-old section of wood of `Royal Gala' trees growing in New Zealand. Three classes of spurs were sampled: purely vegetative spurs, those that flowered but did not carry fruit, and spurs on which a single fruit was borne. The bourse bud, in which flowers may form for the following year's crop, was dissected and bud appendages classified and counted. In addition, axillary buds from current-season shoots were sampled and dissected. Over the period 50–200 days after full bloom, the number of appendages in buds on vegetative spurs increased from ≈14 to 22, whereas the increase in buds on fruiting spurs was 14 to 20. In contrast, axillary bud appendage numbers increased from ≈11 to 14 over this period. By the end of the growing season, flowers were evident in a high proportion of buds of all classes. The critical appendage number at which the change from a vegetative to floral status became visible was ≈18 for spurs on 1-year-old wood, but 13 for axillary buds. The time at which flowers were able to form varied among years. The degree of flower differentiation that occurred prior to leaf fall was highest in vegetative buds and was reduced by flowering and fruiting, and was lowest in axillary buds.

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Raul De la Rosa, Luis Rallo, and Hava F. Rapoport

In the olive (Olea europaea L.), inflorescence and flower differentiation occur in the early spring following a period of winter chilling and dormancy of the potentially reproductive buds. We examined the size, structure, and starch content of these buds during winter rest in the field and during forcing under standard growth-chamber conditions. Basic bud structure and dimensions remained unchanged during the rest period, but starch content increased in the bud's central axis. When cuttings were forced in the growth chamber, the buds followed a morphogenetic pattern similar to that observed in the field, but the sequence of developmental events could be timed more precisely. The first changes observed were the onset of axis growth and the differentiation of axillary primordia within 3 days of transfer to the growth chamber. This was followed by the initiation of new nodes, and, at 15 to 18 days, by the first signs of floral differentiation in the terminal and axillary bud apical meristems. Bud growth and differentiation were accompanied by a decrease in starch content.

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Norberto Maciel and Richard Criley

The colorful and pendulous inflorescence of Heliconia rostrata Ruiz & Pavon terminates an erect and herbaceous-musoid axis of a sympodial rhizome system. Each hapoxanthic axis bears a variable number of leaves (5 to 10) subtending the inflorescence. The number depends on the time between shoot emergence and flowering stimulus. Inflorescence initiation and development occurs without external evidence of this process until the inflorescence emerges from the pseudostem. The morphological changes occurring at the terminal shoot apex of the H. rostrata as it changes from vegetative to the flowering stage are described and illustrated by photomicrographs in this paper. The anatomical sections reveal that the apex on vegetative phase is domed, and a maximum of four furled leaves including one leaf primordium can be observed surrounding it. The growth of the leaf primordium is highly synchronized with growth of the most recently formed leaves. With the transition to inflorescence development, more primordia are observed on the apex, which ultimately give rise to the bracts. Except for the first sterile bract, a cincinnus primordium (flower cluster) is detectable in the axil when the next bract begins to develop. Flower differentiation on the cincinnus begins when many bracts are well-developed. The increase of longitudinal height on the internodes is among the first detectable morphological changes in the apex. Under inductive conditions, the transition to the reproductive stage is achieved early in plants with three or more unfurled leaves. The reproductive plant status is easier to detect under the microscope when the inflorescence has at least three bracts.