arabidopsis, FT is also a point of integration of floral-promoting and -inhibiting signals initiated by vernalization, gibberellins, and plant developmental signals ( Samach et al., 2000 ). In citrus, floral induction is generally considered to be
Eduardo J. Chica and L. Gene Albrigo
Neil O. Anderson
The increasing number of crops being grown for the floriculture market has frustrated educators faced with limited classroom and laboratory time. Time constraints necessitate selection of crops to serve as examples of floral induction treatment(s) and provide an accurate scope of production requirements for all cultivated species. Since flowers are the primary reason for purchasing most floricultural products—with the notable exception of cut and potted foliage—the various treatments required for flower bud initiation and development were used to categorize potted plants. New and old crops (>70 species) are categorized for flower bud initiation and development requirements, including photoperiod (short, long day, day neutral; facultative/obligate responses), vernalization, temperature, autonomous, rest period, and dormancy. Crop-specific temperature, irradiance, and photoperiod interactions are noted, as well as temperature × photoperiod interactions. A course syllabus can be modified to ensure that at least one crop from each category is presented to serve as a model. It is recommended that the class focuses on example crop(s) from each floral induction category and then reviews other crops within each category for differences or similarities. This method allows coverage of floral induction categories without leaving information gaps in the students' understanding. This method was used with students in the Fall 1999, floriculture production class (Hort 4051) at the University of Minnesota, St. Paul.
Xiuren Zhang, David G. Himelrick, Floyd M. Woods, and Robert C. Ebel
`Chandler' strawberry plants (Fragaria Xananassa Duch.) were greenhouse grown under natural lighting and then placed into growth chambers at two constant temperatures of 16 and 26 °C and 2 daylengths of 9 h (SD) and 9-h photoperiod (NI) which was night interrupted with 3 hours of incandescent radiation at 30-45 μmol·s-1·m-2 PAR. Plants were given different numbers of inductive cycles in growth chambers and then moved to the greenhouse. Flowering and growth were monitored. Flowering was completely inhibited at 26 °C, regardless of pretreatment growing conditions such as pot sizes and plant ages, photoperiod, and inductive cycles. At 16 °C, SD promoted floral induction compared to NI under all inductive cycles except a 7-day induction. The minimum number of inductive cycles required at 16 °C for floral induction was dependent on photoperiod and prior greenhouse treatment. Flowering rate was also affected by greenhouse treatment, photoperiod, and inductive cycles. Runner production was affected by photoperiod and temperature × inductive cycle.
Olivia M. Lenahan, Matthew D. Whiting, and Donald C. Elfving
This paper reports on the potential of gibberellic acid (GA3 and GA4+7) to reduce sweet cherry (Prunus avium L.) floral bud induction and balance fruit number and improve fruit quality in the season following application. In 2003, GA3 was applied to `Bing'/`Gisela 1' trees at 50 and 100 mg·L-1 at the end of stage I of fruit development, end of stage II, and on both dates. These treatments were compared to the industry standard application of 30 mg·L–1 applied at the end of stage II and an untreated control. Fruit quality was evaluated in the year of application (i.e., nontarget crop) and return bloom, fruit yield and quality were assessed in the subsequent season (2004). In 2003, GA3 delayed fruit maturity proportional to rate. In 2004, bloom density and fruit yield were related negatively and linearly to GA3 concentration. GA3 reduced the number of reproductive buds per spur and did not affect the number of flowers per reproductive bud. Nonspur flowering at the base of 1-year-old shoots was more inhibited by GA3 than flowering on spurs. Double applications significantly reduced bloom density and yield versus single applications. Trees treated with two applications of 50 and 100 mg·L–1 yielded fruit with 7% and 12% higher soluble solids, 15% and 20% higher firmness, and 7% and 14% greater weight, respectively. However, no treatment improved crop value per tree. In a separate isomer trial, GA3 and GA4+7 were applied to `Bing'/`Gisela 1' trees at 100 and 200 mg·L–1 at both the end of stage I and II in 2004. GA3 and GA4+7 applied at 100 mg·L–1 reduced bloom density similarly by 65%. GA3was more inhibiting than GA4+7at 200 mg·L–1, reducing bloom density by 92% versus 68%. We observed a 4- to 5-day delay in flowering from both GA formulations at 200 mg·L–1. At both concentrations, GA3 reduced yield by 71% and 95% versus 34% and 37% reduction by GA4+7. Fruit weight and soluble solids were unaffected but fruit firmness was increased by all treatments (6% to 17%). However, crop value per tree was highest from untreated control because improvements in fruit quality were insufficient to offset reductions in yield. GA3 shows potential as a novel crop load management tool in productive `Bing' sweet cherry orchard systems.
Fernando Ramírez, Thomas L. Davenport, Gerhard Fischer, and Julio Cesar Augusto Pinzón
-Elisea, 1997 ; Núñez-Elisea and Davenport, 1995 ). The age of the last flush of vegetative stems, thus, appears to be the primary factor regulating floral induction in warm climates. Bueno and Valmayor (1974) indicated that leaves must become brittle as
Ryan M. Warner and John E. Erwin
Thirty-six Hibiscus L. species were grown for 20 weeks under three lighting treatments at 15, 20, or 25 ± 1.5 °C air temperature to identify flowering requirements for each species. In addition, species were subjectively evaluated to identify those species with potential ornamental significance based on flower characteristics and plant form. Lighting treatments were 9 hour ambient light (St. Paul, Minn., November to May, 45 °N), ambient light plus a night interruption using incandescent lamps (2 μmol·m-2·s-1; 2200 to 0200 hr), or ambient light plus 24-hour supplemental lighting from high-pressure sodium lamps (100 μmol·m-2·s-1). Five day-neutral, six obligate short-day, six facultative short-day, three obligate long-day, and one facultative long-day species were identified. Fifteen species did not flower. Temperature and lighting treatments interacted to affect leaf number below the first flower and/or flower diameter on some species. Hibiscus acetosella Welw. ex Hiern, H. cisplatinus St.-Hil., H. radiatus Cav., and H. trionum L. were selected as potential new commercially significant ornamental species.
R. Fernandez-Escobar, M. Benlloch, C. Navarro, and G.C. Martin
GA3 scaffold injections applied between May and November to nonbearing olive (Olea europea L.) trees inhibited flowering the following year, increased shoot width when applied in May, June, and July, and increased inflorescence length when applied in November and February. Fruit removal and seed destruction were effective in improving the return bloom in `Manzanillo' olives when done before endocarp sclerification. Depending on-the year, endocarp sclerification takes place 7 to 8 weeks after full bloom (AFB), usually about 1 July. Fruit removal had no effect on flowering when done after this time. Scaffold injection of paclobutrazol applied to bearing trees between May and September did not affect flowering the following year. The results of our research supports the hypothesis that olive flower induction occurs around the time of endocarp sclerification. Chemical names used: gibberellic acid (GA3), (2RS,3RS)-1-(4-chlorophenyl)-4-dimethyl-2-1,2-4-triazol-1-yl) pentan-3-ol(paclobutrazol).
Gilles Galopin, Laurent Crespel, Jean C. Mauget, and Philippe Morel
to floral induction. Thus, temperatures below 18 °C ( Bailey and Weiler, 1984 ; Post, 1942 ) and a short photoperiod of less than 12 h ( Guo et al., 1995 ; Morita et al., 1980 ; Shanks et al., 1986 ) are favorable to floral transformation. Despite