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- Author or Editor: A.A. De Hertogh x
- Journal of the American Society for Horticultural Science x
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.
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.
Dutch-grown `Deutschland', `Fanal', and `Rheinland' Astilbe, harvested 1 Nov. 1992 and shipped to the United States, were dissected to determine the stage of floral development after 0, 2, 4, 6, 8, 10, 12, or 15 weeks of 2C storage. Astilbe crowns were also planted after 15 weeks of 2C storage and floral development was determined after 1, 2, or 3 weeks of greenhouse forcing. On arrival, multiflower inflorescences were clearly visible. A pattern of abortion and reinitiation occurred during 2C storage. Floral development was markedly repressed when ecodormancy was imposed, but development resumed during greenhouse forcing. During the observational period, floral organ numbers were variable, and morphological abnormalities were observed. In a second experiment, physiological maturity of the crowns was evaluated by harvesting crowns of `Bumalda', `Europa', `Federsee', and `Rheinland' on 15 Sept., 1 Oct., 15 Oct., 1 Nov., and 15 Nov. in The Netherlands. Optimal harvest period was from 1 Oct. to 1 Nov., depending on the cultivar. Crowns harvested before this period were physiologically immature. Crowns harvested during the 4-week window produced the highest overall plant quality and performed as physiologically mature crowns. Astilbe crowns harvested after the 4-week window produced plants with lower forcing qualities and were determined to be beyond the optimal physiological state for forcing.
Abstract
Flowering of ‘Kees Nelis’ (Tulipa gesneriana L.) tulip bulbs was not impaired after 4 weeks of storage at 17°C in either 3 or 5% oxygen. ‘Kees Nelis’ bulbs stored in air or 1% O2 for 4 or 6 weeks and ‘Prominence’ bulbs stored at any reduced O2 level for 4 or 6 weeks flowered unsatisfactorily. Bulbs specially precooled later in the forcing season yielded unsatisfactory flowering after storage at 17°C regardless of cultivar. Low O2 levels (1 to 5%) reduced the respiration rate of bulbs stored at 17°C for 6 weeks compared to bulbs stored in air. Storage of ‘Kees Nelis’ bulbs for 3 weeks in air with 5 ppm ethylene caused flower abortion upon forcing. Three or 5% O2 reduced ethylene-induced flower abortion during storage.
Abstract
The effects of a 63° period of development prior to cooling on the forcing of Lilium longiflorum were compared with precooling treatments. Different bulb sizes of ‘Ace’ and ‘Nellie White’ lilies were used. It was found that a growing period at 63° prior to cooling significantly increased the number of leaves and floral buds. It had no consistent effect on the number of days to flower or final plant height.
With the ‘Ace’ lily, the greatest number of floral buds was observed with a treatment of 3 weeks at 63° followed by 5 weeks at 38°. Within a single bulb size, the ‘Ace’ lily produced more floral buds, was a taller plant, and had more leaves than ‘Nellie White’. The number of leaves and floral buds increased with an increase in bulb size regardless of the type of low temperature treatment or cultivar used.
Abstract
Procedures are described for critical point drying the shoot apical meristems of Easter lilies for viewing in the scanning electron microscope. This preparatory technique was superior to either freeze-drying or the use of freshly isolated meristems. Photomicrographs of the morphological development of the entire shoot apex from the vegetative through several reproductive stages are presented. The morphology of a single flower is also illustrated.
Meristem diameter measurements revealed seasonal and bulb source variations. Diameter increased with increasing bulb size. When compared to non-cooled bulbs, low temperature treatments reduced meristem diameter prior to flower initiation. The average date of flower initiation of controlled temperature forced ‘Ace’ lilies over a 5-year period was January 21; whereas precooled lilies initiated about 1 week earlier. Greenhouse temperatures of 17−25°C accelerated the date of flower initiation when compared to 13°. A simplified technique for measuring the meristem diameter and observing the stage of development was developed.
The Easter lily forms 2 classes of primary flowers, initial and raised. They can also form secondary flowers. The number of initial primary flowers was correlated with meristem diameter. Larger bulb sizes resulted in a greater number of raised primary flowers. In general, only large bulbs formed secondary flowers. A greenhouse temperature of 13°C promoted the formation of raised primary flowers, while 21° promoted the formation of secondary flowers.
A measurement of the sprouting index showed seasonal and bulb source differences.
Abstract
Potted ‘Ace’ lily bulbs were treated with gibberellic acid (GA3) as a soil drench using varying concentrations, numbers of applications and at different stages of development. There was no consistent effect on the forcing days to flower, plant height or the number of leaves, however, specific treatments with 1000 ppm significantly reduced the number of floral buds initiated. It appears that the most sensitive stage of application is that period just prior to flower initiation and that the GA3 must be applied at this time in order to reduce the number of floral buds initiated. A preliminary experiment indicated that GA4+7 was more effective than GA3. GA4+7 influenced plant height and leaf length as well as the number of floral buds but had no effect on the forcing days to flower.
Abstract
Factors affecting floral stalk elongation of tulips during the period from floral bud coloring (budded flower) to the senescence of the perianth were studied. All internodes elongated, however, the greatest elongation occurred in the internode directly beneath the flower and most of the elongation occurred in the upper two-thirds of the internode. Cut tulips elongated less than plants left in the forcing flats. Removal of the budded flower inhibited elongation of the last internode while removal of the leaves was stimulatory with some cultivars. With cut tulips, the perianth appeared to be the primary organ controlling floral stalk elongation followed by the gynoecium and androecium. When the flowers were left intact on the plant the gynoecium exerted the greatest control followed by the perianth and androecium. When the complete flower was removed and IAA or NAA was applied as a lanolin paste to replace the flower, the last internode elongated in a manner similar to the intact flower. Similar applications of kinetin and GA3 were ineffective.