Citrus flowering is a complex phenological process influenced by a number of interacting factors. Low winter temperatures are recognized as an important factor, but the flowering response has not been quantified under Variable natural conditions. A study was conducted to monitor the flower bud induction response of `Valencia' and `Hamlin' sweet orange trees [Citrus sinensis (L.) Osbeck] to naturally occurring winter weather conditions during the 1999 and 2000 seasons. The flowering response was quantified and related to shoot age, bud position along the shoot, local weather information, and crop load status. Results indicate that buds on previous summer shoots developed 2.52 and 3.59 to 1 flower on spring shoots, for `Hamlin' and `Valencia', respectively. In addition, buds at apical positions produced more flowers than buds located far from the apex. These basal positions buds required higher induction levels. Under Florida conditions, greater accumulation of hours of temperatures 11 to 15 °C increased floral intensity by the combined effect on the number of sprouting buds with reproductive growth and the number of flowers per flowering bud. Some statistical analyses indicated that high winter temperatures reduced flowering in `Valencia' and `Hamlin' oranges. The presence of fruit consistently reduced reproductive response for both cultivars. Crop load reduced flowering by an average of 41.5% compared to no crop and varied by cultivar. A discussion on the different induction requirements as well as on the differential effect of crop load on flowering by cultivar is presented.
Juan I. Valiente and L. Gene Albrigo
Rodney Serres and Brent McCown
The capability to uniformlyinduce flowering in cranberry (Vaccinium macrocarpon Ait. `Stevens') in < 1 year from microculture was investigated to accelerate cranberry breeding and to study woody plant reproductive biotechnology. Flower buds were induced on newly micropropagated cranberry plants during the first growing season. A treatment of 2.5 mg of paclobutrazol applied as a soil drench per 2- to 3-month-old potted plant in midsummer, when the plants were grown in coldframes under natural daylength and air temperatures, resulted in 70% of the plants flowering. Plants not treated with paclobutrazol did not flower. Reduced but significant flower bud set was observed on plants treated with paclobutrazol but grown in the greenhouse under natural daylength. Flowering was stimulated by cold treatment coupled with gibberellin sprays and/or repotting to nonpaclobutrazol-treated medium. Chemical name used: β -[(4-chlorophenyl)methyl]-ct-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).
L. Gene Albrigo
Three hurricanes in Florida starting in late Summer 2004 caused severe leaf loss, which stimulated many fall shoots. Flush occurred after each hurricane and by December, shoots were 6- to 12-weeks-old when cool temperatures capable of causing flower bud induction started. To evaluate the potential for these flushes to mature buds that could be induced to flower, flushes that were stimulated on potted trees in a greenhouse were allowed to mature 4, 6, 8, or 10 weeks before moving trees to flower-inducing conditions for 6 weeks (15 °C day/10 °C night). Plants were then returned to the greenhouse, which was kept at 20 °C or higher (ambient), until buds sprouted. Only 1% of sprouting buds on shoots that matured for 4 weeks had flowers. In shoots that matured for 6 weeks, 18% of sprouting buds had flowers. After 8 weeks of growth, 57% of the buds that sprouted were flower buds, while after allowing 10 weeks for shoots to mature, induction resulted in 76% of the sprouting buds producing flowers. Consequently, 8 weeks of development were necessary for citrus shoots to develop mostly mature buds that responded to flower inductive conditions. This is about the same amount of time required for new citrus leaves to fully mature.
Jiwei Ruan, Guoxian Wang, Gongwei Ning, Chunmei Yang, Fan Li, Linmeng Tian, and Lifang Wu
’ should be developed according to the local climate and production systems. Plant nutrient status, especially N status, is another factor that influences flower bud induction ( Guttridge, 1985 ). In general, less N can promote flower bud induction ( Seo et
Jinxin Wang, Tao Luo, He Zhang, Jianzhu Shao, Jianying Peng, and Jianshe Sun
promoted flower bud induction ( Li et al., 1996 ). However, the low level of IAA was beneficial to flower formation ( Cao et al., 2000 ; Wang et al., 1989 ). Our results showed that the content of IAA increased slowly during the physiological
Fumiomi Takeda, D. Michael Glenn, and Gary W. Stutte
red light from LED lamps directed at the crown delayed flower bud induction in ‘Strawberry Festival’ strawberry. Flower bud emergence was observed in only 17% of plants compared with 38% of control (unlit) plants on 19 Sept. (data not presented). For
Ying Gao, Hao Liu, Ningguang Dong, and Dong Pei
flower formation in perennial woody plants has been studied by high-performance liquid chromatography [HPLC ( Guo et al., 2010 ; Li et al., 1996 ; Liu et al., 2007 )], which indicated that high levels of IAA promote flower bud induction in apple trees
Juan Carlos Melgar, Jill M. Dunlop, L. Gene Albrigo, and James P. Syvertsen
. 2004 Flower bud induction, flowering and fruit-set of some tropical and subtropical fruit tree crops with special reference to Citrus Acta Hort. 632 81 90 Bain, J.M. 1958 Morphological, anatomical, and physiological
Eduardo J. Chica and L. Gene Albrigo
signals from the floral pathway integrator FT at the shoot apex Science 309 1052 1056 Albrigo, L.G. Galen-Saúco, V. 2004 Flower bud induction, flowering and fruit-set of some tropical and subtropical fruit tree crops with special reference to citrus Acta
Takashi Ikeda, Keisuke Yamazaki, Hiroshi Kumakura, and Hiroshi Hamamoto
the terminal inflorescence had already started during cold storage (i.e., flower bud induction treatment). Because there were no duration of flower bud emergence on the terminal inflorescence (data not shown), it might have been possible to transplant