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Nobuhiro Kotoda, Masato Wada, Sadao Komori, Shin-ichiro Kidou, Kazuyuki Abe, Tetsuo Masuda and Junichi Soejima

Two apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] homologous fragments of FLO/LFY and SQUA/AP1 (AFL and MdAP1, respectively) were analyzed to determine the relationship between floral bud formation and floral gene expression in `Jonathan' apple. The AFL gene was expressed in reproductive and vegetative organs. By contrast, the MdAP1 gene, identified as MdMADS5, which is classified into the AP1 group, was expressed specifically in sepals concurrent with sepal formation. Based on these results, AFL may be involved in floral induction to a greater degree than MdAP1 since AFL transcription increased ≈2 months earlier than MdAP1. Characterization of AFL and MdAP1 should advance the understanding of the processes of floral initiation and flower development in woody plants, especially in fruit trees like apple.

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Samuel Salazar-García, Elizabeth M. Lord and Carol J. Lovatt

Inflorescence and flower development of the `Hass' avocado (Persea americana Mill.) were investigated at the macro- and microscopic level with three objectives: 1) to determine the time of transition from vegetative to reproductive growth; 2) to develop a visual scale correlating external inflorescence and flower development with the time and pattern of organogenesis; and 3) to quantify the effect of high (“on”) and low (“off”) yields on the flowering process. Apical buds (or expanding inflorescences) borne on summer shoots were collected weekly from July to August during an “on” and “off” crop year. Collected samples were externally described and microscopically analyzed. The transition from vegetative to reproductive condition probably occurred from the end of July through August (end of shoot expansion). During this transition the primary axis meristem changed shape from convex to flat to convex. These events were followed by the initiation of additional bracts and their associated secondary axis inflorescence meristems. A period of dormancy was not a prerequisite for inflorescence development. Continued production of secondary axis inflorescence meristems was observed from August to October, followed by anthesis seven months later. In all, eleven visual stages of bud development were distinguished and correlated with organogenesis to create a scale that can be used to predict specific stages of inflorescence and flower development. Inflorescence development was correlated with minimum temperature ≤15 °C, whereas yield had little effect on the timing of developmental events of individual inflorescence buds. However, the high yield of the “on” year reduced inflorescence number and increased the number of vegetative shoots. No determinate inflorescences were produced during the “on” year. For the “off” year, 3% and 42% of shoots produced determinate and indeterminate inflorescences, respectively.

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Valentina Schmitzer, Robert Veberic, Gregor Osterc and Franci Stampar

al., 2008a ; Mayak and Halevy, 1972 ; Sood and Nagar, 2003 ). Little information is available on phenolic content of developing rose petals. Sood and Nagar (2003) observed a sharp increase during flower development from the flower bud opening to

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Zhen Shu, Yimin Shi, Hongmei Qian, Yiwei Tao and Dongqin Tang

their flower development and senescence. The aim of our present study was to comparatively characterize the respiratory and physiological changes during flower development and senescence in Freesia hybrid and to provide physiological basis for its

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Valentina Schmitzer, Robert Veberic, Gregor Osterc and Franci Stampar

bound phenols as well as total anthocyanins in rose petals and measured an increase in the initial stages of flower development, followed by a decrease at the fully open stage. However, in these studies on cut rose flowers, no data were reported on the

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M. Oren-Shamir, L. Shaked-Sachray, A. Nissim-Levi and D. Weiss

Little is known about the effect of growth temperature on Aster (Compositae, Asteraceae) flower development. In this study, we report on this effect for two aster lines, `Suntana' and `Sungal'. Growth temperature had a dramatic effect on the duration of flower development, ranging from 22 days for plants growing at 29 °C up to 32 days for plants grown at 17 °C. Flower longevity was ≈40% shorter under the higher temperature for both lines. Growth temperature also affected flowerhead form: `Suntana' flowerhead diameter was 20% larger at 17 °C than at 29 °C. The number of `Sungal' florets per flowerhead was four times greater at the lower temperature. Shading (30%) under temperature-controlled conditions had no effect on any of the parameters measured. For plants grown outdoors, our results suggest that shading plants may increase quality by reducing the growth temperature.

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L. C. Cushman, H. B. Pemberton and J. W. Kelly

Orange end Red Sunblaze miniature rose plants were forced. to flower in a glasshouse in 10 cm pots. At harvest, flower stage (FST) 1 (tight bud), 2 (reflexed calyx), and 3 (petals starting to reflex) flowers were designated and tagged. The plants were then stored at 4, 16 or 28°C for 2, 4, or 6 days. Subsequent to the simulated shipping treatments, plants were evaluated in a simulated home interior environment (21° with 30 μmoles M-2 sec-1 cool-white fluorescent light). After summer forcing, flowers of both cultivars developed at least 1 FST during simulated shipping. Flower development increased as storage duration increased for FST 1 and 2, but storage duration did not affect development of FST 3 flowers. The higher the temperature the faster flowers developed, but development was less than 1 FST at 4°. After winter forcing, flowers developed less than 1 FST during simulated shipping. Flower development increased with increasing temperature. In summer, plants with FST 2 flowers could be shipped at up to 16°, but plants with FST 3 flowers should be shipped at 4°. In winter, plants can be shipped at up to 16° with FST 3 flowers.

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Z. Wang, M.C. Acock and B. Acock

Flower development in opium poppy (Papaver somniferum L.) has been divided into four phases from emergence to anthesis, which mark changes in its sensitivity to photoperiod: a photoperiod-insensitive juvenile phase (JP), a photoperiod-sensitive inductive phase (PSP), a photoperiod-sensitive post-inductive phase (PSPP), and a photoperiod-insensitive post-inductive phase (PIPP). To predict flowering time under field conditions, it is essential to know how these phases are affected by temperature. Plants were grown in artificially lit growth chambers and received three temperature treatments: 15/10, 20/15, and 25/20°C in a 12-hr thermoperiod. Plants were transferred within each temperature regime from a non-inductive 9-hr to an inductive 16-h photoperiod or vice versa at 1- to 4-day intervals to determine the durations of the four phases. Temperature did not affect the durations of the first two phases (i.e., JP lasted 3 to 4 days and PSP required 4 to 5 days). The most significant effect of temperature was on the duration of PSPP, which lasted 28, 20, and 17 days at 15/10, 20/15, and 25/20°C, respectively. The temperature effect on PIPP was small (maximum difference of 3 days for treatments) and the data too variable to indicate a significant trend. Our results indicate that PSPP is the only phase that clearly exhibits sensitivity to temperature.

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Julie A. Plummer, T. Eddie Welsh and Allan M. Armitage

Zantedeschia aethiopica (L.) K. Spreng. `Childsiana' is a dwarf white calla lily with potential for pot culture. Nine stages of flower development from macrobud to senescence were described and shelf life under a low-light postproduction environment was examined. Flowers at the macrobud stage opened in the postproduction environment. Plants with flowers at the macrobud stage (Stage 1) and plants with spathes fully opened but before pollen shed (Stage 5) had shelf lives of 26 and 11 days, respectively.

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Z. Wang, M.C. Acock and B. Acock

Flower development in opium poppy (Papaver somniferum L. `album DC') is enhanced by long photoperiods (PP ≥ 16-hours). Predicting time to flower in field-grown opium poppy requires knowledge of which developmental stages are sensitive to PP and how the rate of flower development is changed by changes in PP. The objective of this work was to determine when poppy plants first demonstrated developmental changes in response to PP and how long PP continued to influence the time to first flower under consistent temperature conditions. Plants were grown in artificially lit growth chambers with either a 16- (inductive) or a 9-hour PP (noninductive). Plants were transferred at 1 to 3-day intervals from a 16- to a 9-hour PP and vice versa. All chambers were maintained at a 12-hour thermoperiod of 25/20°C. Poppy plants demonstrated developmental changes in response to PP four days after emergence and required a minimum of four inductive cycles before the plant flowered. Additional inductive cycles, up to of a maximum of nine, hastened flowering. After 13 inductive cycles, flowering time was no longer influenced by PP. These results indicate four phases between emergence and first flower: 1) a photoperiod-insensitive juvenile phase (JP); 2) a photoperiod-sensitive inductive phase (PSP); 3) a photoperiod-sensitive post-inductive phase (PSPP); and 4) a photoperiod-insensitive post-inductive phase (PIPP). The minimum durations (days) of these phases under the conditions of our experiment were JP = 4, PSP = 4, PSPP = 9, and PIPP = 14.