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- Author or Editor: A.A. De Hertogh x
Abstract
At the University level, horticulture is one of the most dynamic fields in Agriculture. Undergraduate student enrollments, both for majors and nonmajors, have never been higher. The number of requests for graduate student assistantships are increasing. Extension personnel are under constant pressure from their clientele for more and more programs and information. The requirements for research have never been greater. In addition, with the democratic system which has been developed, scientists are spending more time on administrative matters than ever before. All of these points have their advantages and disadvantages but the time is past due for a detailed analysis of their impact on our programs by the individuals who are directly involved in carrying out the research, teaching, and extension functions. This is particularly true for those of us in the field of floriculture and ornamental horticulture.
Abstract
Exercises are described to familiarize horticultural students with the ‘Standard Forcing’ of potted tulips, hyacinths, daffodils, Iris reticulata, Crocus and grape hyacinths as well as cut tulips and daffodils. Procedures are outlined for ‘Special Precooling’ of tulips and Dutch iris as cut flowers. In addition, a simplified list of readily available cultivars of the spring-flowering bulbs covered is provided. The exercises utilize Valentine’s Day as the marketing holiday.
Abstract
This column has had articles on many subjects that need to be addressed, e.g., funding research (4), horticultural education (2), professions in horticulture (5), and interdisciplinary research (3). After reading these articles, and I encourage all members to do so, I came to the conclusion that they tend to concentrate on only one point. The question remains: what is the primary mission of horticultural science? I believe that the answer is simple and straightforward: to service production horticulture. This was the original purpose of establishing the land-grant university system and the USDA-Agricultural Research Service. It remains our primary mission and horticultural scientists must not lose sight of it.
Abstract
Cell-free extracts which incorporated mevalonate-2-14C (MVA) into terpenes were obtained from shoot tissue of Tulipa gesneriana L. cv. Golden Melody. Maximal incorporation occurred at pH 6.5 in 0.1 M KH2 PO4-K2HPO4 buffer with an incubation temperature of 35°C. Total incorporation was linear up to 5 mg protein/assay and it could be enhanced by increasing MVA concentration up to 8 × 10-8 M. After differential centrifugation, all enzymatic activity was located in the 100,000 × g supernatant. In combination Mg++ and Mn++, ATP stimulated incorporation more than CTP, GTP, and UTP. Using ATP as the energy source, Mn++ was highly stimulatory at 1 and 5 × 10-3 M. Mg++ alone or in combination with Mn++ was less effective than Mn++.
The radioactivity from MVA was recovered in 2 fractions: the “neutral” fraction isolated by extraction with benzene, and the “acid hydrolyzable” fraction extracted with benzene after acid hydrolysis of the residual aqueous “neutral” fraction. For subsequent identification of the neutral terpene products, the optimal conditions are either high protein concentration (18 mg/assay) after a 15,000 × g centrifugation and a 4-hr incubation period or high protein concentration without centrifugation and a 1-hr incubation period. The optimal conditions for identification of the acid hydrolyzable products are low protein concentration (5 mg/assay) and 1-hr incubation.
Abstract
Potted ‘Ace’ lily bulbs were treated with 1000 ppm of either gibberellin A3 (GA3) or gibberellins A4+7(GA4+7) as a soil drench using 200 ml per pot on January 6, 1971. GA treatments had no effect on the time of floral initiation, however, GA3 decreased the days to flowering when compared to either GA4+7 or water controls. GA4+7 and GA3 reduced the number of primary flowers initiated. and completely inhibited the initiation of secondary flowers. GA4+7 increased the number of primary flowers which aborted shortly after initiation and GA3 did not. Both GAs increased plant height; GA4+7 had the greater effect. GA4+7 significantly reduced the length of the lower leaves, but none of the treatments affected the number of leaves produced.
Abstract
Using a standard forcing program for early February flowering, the histogenesis of the tulip apical meristem from the vegetative state to the differentiated, immature flower was observed with the scanning and light microscopes. Root and central bulblet development were observed only with the light microscope. Total scape and root growth were measured from initiation to anthesis. The apex was vegetative on July 21, prefloral on August 1, and reached the reproductive stage “G” on August 15. The first internode was formed by August 7 and the last internode was formed just prior to reaching stage “G”. Cell division was observed in the scape from formation until after planting at 9°C. A second phase occurred in the epidermal cells, nodal regions, and vascular bundles immediately after the plants were placed in the greenhouse. It preceded the rapid rate of cell elongation in the scape. Root initiation had commenced by late July. Root growth and differentiation continued in the basal plate until mid-September, resumed during the cold treatment, and continued after the plants were placed in the green-house. The central bulblet was initiated by early August and continued to develop throughout the forcing program.
Abstract
Dutch-grown tuberous-rooted dahlias, ‘Kolchelsee’ and ‘Park Princess’, were forced from January to June in 1975 and 1976. In all experiments, plant height was controlled by applying 0.5 mg/pot of ancymidol 2 weeks after planting.
Fertilization was essential and an application of one of several slow-release formulations of Osmocote or weekly applications of 20N—8.8P—16.6K (200 ppm N) as a soluble fertilizer produced high quality plants which flowered in approximately 70 days. The highest quality plants and best height control was obtained with 25°C day and 16° night temperatures. Flowering was delayed at 24/12° day/night temperatures, and although flowering was accelerated at 28/17° and 29/20° day/night temperatures plant quality was adversely affected.
Natural spring photoperiods which increased from 10 to 14 hours were optimal for forcing. Long days given either as a 16-hour photoperiod or as a 4-hour night break delayed flowering slightly. Dahlias grown under an 8-hour photoperiod flowered the earliest but not all plants flowered. Dahlias required high light intensities during forcing. Under 50% shading plants were too tall for pot plant use even after treatment with ancymidol.