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- Author or Editor: Anton M. Kofranek x
Garden chrysanthemums [Dendranthemum ×grandiflorum (Ramat.) Kitamura] are characterized by early flowering in September and October when grown out-of-doors and by rapid flowering in short days (SD). However, as rooted cuttings of these cultivars frequently have flower buds present at the time of planting, their true response to daylength cannot readily be determined. Vegetative shoots were obtained by growing rooted cuttings in long days (LD), removing the terminal bud, and then pinching the emerging side shoots at a very early stage. On transfer to SD, the vegetative secondary side shoots quickly initiated flower buds that developed to anthesis more rapidly than those of `Bright Golden Anne' (BGA), a lo-week response group cultivar. `Bandit', `Buckeye', `Compatriot', `Freedom', `Jackpot', and `Sunburst Cushion' appeared to be in the 7-week response group, with `Baby Tears' in the 6-week and `Powder River' in the 8-week response groups. All cultivars rapidly initiated flower buds in LD and, although they produced significantly more leaves than in SD, flower initiation began within ≈13 LD from pinching. When pinched twice and grown using black cloth in summer, garden chrysanthemums can form attractive, uniformly flowering pot plants. Their rapid-flowering characteristic could also be of value in breeding programs for cut-flower chrysanthemums.
Abstract
Net photosynthesis, as measured by dry matter changes, was reduced following the dark periods when foliage plants were grown in extended, alternate dark-light cycles. Longer dark periods resulted in greater reduction; however, recovery was observed if the light duration was increased. No visual quality reduction was observed in Tradescantia fluminensis Veil and Asparagus setaceus Jessop which was grown under 14 days light: 14 days dark cycles for 84 days. Similarly, the quality of mature leaves and stems of Philodendron scandens Subsp. oxycardium (Schott) Bunt grown under 24 days dark: 24 days light cycles for 96 days was not impaired; however, new shoots and leaves were abnormal. Dry matter partitioning of Philodendron was affected by light conditions and growth activity. In plants with no active growth, the dry weight of leaves, stems, and roots was increased under adequate light condition and decreased under darkness. Stems were stronger sinks than leaves. In all treatments, when new shoots started their active growth, they became the main carbohydrate sinks with a concomitant reduction of weight of the mature organs. Reduction in percent dry matter following the lowering of the light intensity was observed. Determining and measuring the critical percent dry matter at which plant injury occurs are suggested as practical methods to evaluate the plant’s condition and how it may respond during and after the marketing period.
Abstract
Frequent irrigation regimes, and cool storage increased the sensitivity of carnation cut flowers to ethylene which was reflected by a shorter residual flower life. A combination of cytokinins, 0.23 m<sc>M</sc> kinetin or isopentyl adenine (IPA), with 5% w/v sucrose reduced the sensitivity to ethylene and increased longevity 2 to 2.6 times, respectively. The reversible and irreversible wilting response to ethylene is discussed.
Abstract
Foliar spray of dikegulac-sodium in a 20% formulation (Atrinal) at concentration of 0.4 and 0.6% active ingredient in aqueous solutions were found to effectively pinch ‘California Sunset’, ‘Chimes’, ‘Dogwood’, ‘Gloria’, ‘Knute Erwin’ and ‘Rose Queen’ evergreen azaleas (Rhododendron simsii Planch.) but not ‘Red Wing’. Pinching was effective under several environmental conditions but was enhanced by late afternoon applications when temperature and light were lower and the relative humidity higher. Atrinal was effective on both vegetative and early reproductive shoots.
Abstract
The relative efficiency of several types of fluorescent lamps (General Electric) for dry matter production was examined both experimentally and by mathematical calculations. The highest yield of Tradescantia fluminensis plants per electrical energy input unit was obtained with Cool White lamps. In comparison to Cool White lamps the yield under other lamps was: Daylight = 88%; Cool White Deluxe = 73%; Plant Light = 72%; Pink + Blue = 36%. Similar results were found using calculations based on the action spectriim for photosynthesis of an “average leaf” proposed by McCree (8), the spectral energy distribution curves of the different lamps and the illuminance (lux) at the plant level. Measurement of the relative efficiency based on input wattage of Cool White (General Electric) and Agro-lite (Westinghouse, F-40/AGRO) fluorescent lamps for dry matter production of 9 foliage plant species showed an average 9% advantage of the Cool White lamp. We propose that fluorescent lamp evaluation for plant growth be standardized using McCree's or Balegh and Biddulph's equation for predicted photosynthetic efficiency.
Abstract
Thirty-eight cultivars of Chrysanthemum × morifolium Ramat. commonly grown in year-round flower production programs were grown continuously in long days. After 19 weeks of growth, 2 apparently were still vegetative, whereas 36 had formed flower buds; these failed to develop to anthesis and formed “crown buds”. The average number of leaves produced before the terminal flower bud (“long-day leaf number,” LDLN) ranged from 18.8 for ‘Bright Golden Anne’ to 78.2 for ‘Dignity.’ LDLN indicates whether a cultivar will form flower buds relatively early while growing in long days, and it identifies cultivars that need special attention during cutting production. It also could be used to control flowering in “timed-pinch” programs, and to characterize cultivars for breeding programs.
Abstract
Cut flowering stems of carnation (Dianthus caryophyllus) in demineralized water were treated at daily intervals with pulses of silver thiosulphate (STS) at 4 mM for 10 minutes or 2 mM for 60 minutes until just before the end of their natural life and were returned to water for observation of flower senescence. Treatments with STS increased flower life most effectively when applied on the day the flowers were cut. It was also effective if applied for up to 3 days after cutting, but less so if applied after this time. The longevity of flowers pulsed with STS compared favorably with those treated continuously with a commercial preservative.
Abstract
Pulsing gladiolus stems at 21°C with 20% sucrose in combination with AgNO3 before storage of 7 or 10 days resulted in greater floret opening and size than those not pulsed. A silver treatment alone was not effective. The sucrose fulfills the requirements for a carbohydrate source and osmoticum which are necessary for floret growth and development. This treatment with sucrose is recommended prior to shipping or storage of gladiolus for long periods.
Abstract
Pot roses (Rosa hyb. cvs. Pink and Orange Margo Koster and Red Garnette) were sprayed with naphthaleneacetic acid (NAA) or 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine (PBA) prior to simulated truck shipment which lasted 5 or 6 days to study the effect on flower bud and leaf abscision and on leaf senescence. “Shipment” under refrigerated conditions (1-3°C) prevented bud and leaf abscission. ‘Red Garnette’ and ‘Orange Margo Koster’ had little or no bud and leaf abscission even at a warm “shipping” temperature (20-22°C); however, ‘Pink Margo Koster’ was severely affected. Observations under “home conditions” for 10 days after this warm “shipping temperature” revealed that all 3 cultivars had severe leaf senescence. NAA spray (15 and 30 ppm) severely accelerated leaf abscission and senescence. NAA prevented bud drop, but the buds did not open. PBA (50 ppm) greatly reduced leaf abscission both during “shipment” and in “home conditions”. PBA also prevented bud drop and flowers subsequently opened normally.
Abstract
The floral initiation response of ‘Paul Mikkelsen’ poinsettia to low temperature under long days was saturated after exposure to constant temperatures of 60°F for 10 days. Low temperature was perceived by the shoots but not the roots. As has been reported by others, high temperatures (80°F) during and after short days inhibited floral initiation. Gibberellin A3 was an effective inhibitor of low temperature stimulated floral initiation under long days and Cycocel promoted flowering under long days at 70°F but not at 80°. Neither light source nor intensity greatly influenced low temperature stimulated floral initiation. These findings are discussed in relation to a possible mechanism by which low temperatures stimulate floral initiation in this short day plant and in relation to cultural practices.