The transition from vegetative growth to reproductive growth is carefully controlled by a number of independent signal transduction systems, one of which interprets photoperiod. Photoperiodic control of flowering time has been well-described in Arabidopsis and rice, revealing the presence of a generally common network of regulatory proteins. Timely and appropriate progression to flowering is critical to profitable production of cultivated strawberry (Fragaria ×ananassa), a species that includes long-day, short-day, and day-neutral cultivars. In an effort to characterize the photoperiodic flowering control mechanism in strawberry, the Fragaria orthologs of the photoperiod pathway genes were cloned and sequenced. Strawberry versions of Constans, Constans-like, Leafy, Flowering Locus T, and Suppressor of Constans Overexpression 1 were identified by screening cDNA libraries and through degenerate PCR approaches. Expression of these transcripts in short-day and day-neutral cultivars was tested under long and short photoperiods. Functional complementation of Arabidopsis mutants was performed where appropriate, alleles were identified, genetic linkage was determined where possible, and relationships between the strawberry genes and homologs from other species were studied. These trials define the mechanistic elements of an agriculturally important pathway in this valuable crop, and lays the foundation for transgenic studies in strawberry to manipulate the floral transition.
Philip J. Stewart, Ashley R. Winslow and Kevin M. Folta
Yosuke Yoshioka, Ryo Ohsawa, Hiroyoshi Iwata, Seishi Ninomiya and Naoko Fukuta
Petal shape and picotee colour pattern of lisianthus [Eustoma grandiflorum (Raf.) Shinn.] were qualitatively evaluated by means of personal computer-based methods. In lisianthus, many cultivars have been improved to obtain various floral characteristics. Picotee color patterns and flower shape are commercially important in this species and the availability of an objective and quantitative evaluation method is of vital importance for investigations related to the genetic and physiological aspects of these characteristics. Our objectives were to evaluate petal shape variation quantitatively and to establish a new quantitative evaluation method for picotee color patterns. We succeeded in quantitatively evaluating petal shape variation by means of elliptic Fourier descriptors and principal-components analysis, and in evaluating picotee color patterns by a newly developed procedure based on comparative marginal distribution. Petal shape variation was divided into symmetrical and asymmetrical elements of the entire shape variation. Both groups were additionally divided into several components. The variations in picotee color pattern were effectively described by the first through fourth principal components. Comparing the varietal effect of these components, nested analyses of variance showed that the differences between cultivars in picotee color pattern were smaller than those of the symmetrical shape elements. In addition, the environmental effects on picotee color formation were greater than those of symmetrical shape formation. The evaluation methods described in this study are effective for further investigations, and are applicable to other floricultural crops as well as lisianthus.
John M. Dole and Michael A. Schnelle
Floricultural producers, cut flower wholesalers, mass market retailers and general retailers were surveyed to compare and contrast the industry in terms of attitudes and problems. Questions involved general business information, as well as specific crops. Overall, all four segments of the industry were neutral to negative on potted flowering plants, but were positive to neutral on bedding and foliage plants. However, producers were slightly negative concerning the postharvest life of bedding plants. While cut flower wholesalers had a positive attitude concerning cut flowers, retailers and mass marketers tended to be neutral to negative. In particular, retailers and mass marketers felt cut flowers were too expensive and too short lived. Floral preservatives were used by 81.6% of general retailers, while only 18.8% of mass market retailers used preservatives. All cut flower wholesalers used preservatives. Capital availability and market demand were the factors most limiting to expansion for producers and general retailers; mass market firms listed competition as their most limiting factor. Results from other questions will also be provided.
Zhi-Rong Li, Kang-Di Hu, Fen-Qin Zhang, Shi-Ping Li, Lan-Ying Hu, Yan-Hong Li, Song-Hua Wang and Hua Zhang
Broccoli ( Brassica oleracea var. italica ) is an important vegetable of high nutritional value and a common component of the human diet. Floral heads of broccoli are harvested during the immature stage when florets are composed of male and female
Steven J. McArtney and Dick Unrath
Experiments were carried out in the southeastern United States between 1998 and 2006 to evaluate the potential for applications of NAA, Ethrel, or both, in the on-year of a biennial bearing cycle to increase return bloom in apple. Four bi-weekly applications of 5 ppm NAA beginning in mid June (summer NAA) increased return bloom, measured as the percentage of floral spurs in the year after treatment. The level of return bloom on trees receiving a summer NAA program was more than 2-fold higher than on untreated control trees, averaged across seven different experiments. Four applications of 5 ppm NAA at weekly intervals leading up to harvest (August/September) increased return bloom also. Combining 150 ppm Ethrel with summer NAA sprays resulted in an additive effect on return bloom compared to NAA or Ethrel alone. The effect of flower cluster density on return bloom the following year was more negative on control trees than it was on trees sprayed with Ethrel in the previous year. Treatment effects on fruit maturity at harvest were generally neutral, although flesh firmness was reduced in some experiments. NAA or Ethrel sprays in the on-year of a biennial bearing cycle may provide a strategy for achieving more consistent flowering and cropping in apple.
N. Kuanprasert, A.R. Kuehnle and C.S. Tang
Flowers emit volatile compounds that attract pollinators. In ornamental plant breeding programs, fragrance is a significant character that adds value to flowers for its consumer appeal. In Hawaii, anthurium (Araceae) is an important crop used for cut flowers and flowering potted plants. Unlike other ornamentals, fragrance is not presently associated with commercial anthuriums. However, several anthurium species are known to have distinctive scents. To obtain the novelty trait of fragrance in anthurium, an understanding of anthurium scent genetics, physiology, and chemistry is required. Scented anthurium species and hybrids in the Univ. of Hawaii germplasm collection have been studied. Fragrance emission among species varies with time of day—some species being scented only in the morning, only at night, or all day long. Fragrance emission also varies with stage of spadix development, with some species having scent as pistillate and/or staminate flowers. The species sampled comprise five categories: A. amnicola, A. formosum, and A. lindenianum are minty; A. armeniense is sweet; A. gracile is floral; A. bicollectivum, A. cerrobaulense, A. folsomii, and A. harleyii are fruity; and A. supianum is fishy. Some of the chemical components are illustrated.
Amber L. Robertson*, Karianne M. Kusner and Sara E. Patterson
Abscission, an active process resulting in the removal of an organ from the main body of a plant, occurs naturally in response to pathogens, disease, or when the plant part is no longer needed. Several delayed abscission mutants have been identified from the Univ. of Wisconsin T-DNA tagged mutant populations in Arabidopsis thaliana. One of the identified mutants, dab 5-1, is characterized by a delay in abscission causing the floral organs to remain attached past position ten; however, all other plant functions are normal. dab 5-1 has been thought to be involved in the secretory pathway. The present study was conducted to further characterize dab 5-1 expression at the cellular, tissue, and organelle levels using reporter gene constructs, light microscopy, scanning electron microscopy, and RT PCR. dab 5-1 expression was found in the roots, root tips, cotyledons, meristem, abscission zone, and anthers. Early abscission can lead to loss in yield and quality and we believe that understanding genes such as DAB5 will ultimately lead to crop improvement.
Bin Liu and Royal D. Heins
The objectives of this study were to quantify the effects of the radiant-to-thermal energy ratio (RRT) on poinsettia plant growth and development during the vegetative stage and develop a simple, mechanistic model for poinsettia quality control. Based on greenhouse experiments conducted with 27 treatment combinations; i.e., factorial combinations of three levels of constant temperature (19, 23, or 27°C), three levels of daily light integral (5, 10, or 20 mol/m2 per day), and three plant spacings (15 × 15, 22 × 22, or 30 × 30 cm), from pinch to the onset of short-day flower induction, the relationship between plant growth/development and light/temperature has been established. A model for poinsettia quality control was constructed using the computer software program STELLA II. The t-test shows that there were no significant differences between model predictions and actual observations for all considered plant characteristics; i.e., total, leaf and stem dry weight, leaf unfolding number, leaf area index, and leaf area. The simulation results confirm that RRT is an important parameter to describe potential plant quality in floral crop production.
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.
Beth Ann A. Workmaster, Jiwan P. Palta and Jonathan D. Smith
In Wisconsin, the cranberry plant (Vaccinium macrocarpon Ait.) is protected from freezing temperatures by flooding and sprinkle irrigation. Due to the high value of the crop, growers typically overprotect by taking action at relatively warm temperatures. Our goal is to provide recommendations for improved frost protection strategies by studying seasonal hardiness changes in different parts of the cranberry plant (leaves, stems, buds, flowers, fruit). Stages of bud growth were defined and utilized in the hardiness determinations. Samples were collected from mid-April to mid-Oct. 1996 and cuttings were subjected to a series of freezing temperatures in a circulating glycol bath. Damage to plant parts was assessed by visual scoring and observation, ion leakage, and evaluation of the capability to regrow. The following results were obtained: 1) Overwintering structures, such as leaves, stems, and buds, can survive temperatures <–18°C in early spring, and then deacclimate to hardinesses between 0 and –2°C by late spring. 2) In the terminal bud floral meristems are much more sensitive to freeze–thaw stress than are the vegetative meristems. 3) Deacclimation of various plant parts occurred within 1 week, when minimum canopy temperatures were above 0°C, and when the most numerous bud stage collected stayed the same (bud swell). 4) Fruits >75% blush can survive temperatures of –5°C for short durations. By collecting environmental data from the same location we are attempting to relate plant development, frost hardiness, and canopy temperatures (heat units).