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- Author or Editor: W.C. Lin x
Alstroemeria ‘Regina’ plants were grown for 2 years in soil benches in a greenhouse. Soil cooling to less than 14°C overcame the typical nonflowering of ‘Regina’ plants during the November-May period. High intensity supplementary lighting with high-pressure sodium (HPS) lamps had little effect on or reduced the numbers of flowering shoots produced in noncooled benches. HPS lighting combined with soil cooling increased the number of flowering shoots, the shoot length and the total number of flower buds per shoot, and decreased the absorted flower buds per shoot. The commercial implication of this interaction between soil temperature and supplementary lighting is discussed.
Alstroemeria ‘Regina’ plants were grown at an air temperature of 15°/18°C (night/day). Soil cooling resulted in an increased number of flowering shoots in both spring-summer (21 Mar. to 20 Sept.) and fall-winter (21 Sept, to 20 Mar.) during the first year. Daily 16-hour supplementary lighting with high-pressure sodium (HPS) lamps reduced flowering shoots in spring-summer. In winter, only plants treated with the combination of soil cooling and HPS lighting produced flowers.
Cut flower Gerbera (Gerbera jamesonii Bolus) plants were grown in pots or ground benches under various photoperiods, levels of irradiance, and soil temperatures. Photoperiodic flowering response varied with the 3 cultivars; ‘Appelbloesem’ was not sensitive to photoperiod; ‘Oranje Nasau’ and ‘Fabiola’ were promoted by short day (SD). In pot-grown Gerbera, SD increased the number of flowers (inflorescences) per plant of ‘Oranje Nassau’ and ‘Fabiola’ in the summer-fall and fall-winter. Supplementary lighting with high-pressure sodium (HPS) lamps increased the fall-winter production of all 3 cultivars. Plants grown under 16 hr photoperiod by extending natural day length with incandescent light (INC) produced the least flowers per plant in both summer-fall and fall-winter. In bench-grown Gerbera, supplementary HPS increased the number of flowers during the fall-winter as compared to natural daylight (ND). Soil warming from 16°−20° to 23°C had no effect on productivity, but increased the peduncle length.
Injecting CO2 gas into mist water (CO2 mist) promoted rooting of Ilex aquifolium L. ‘Silver Variegated Standard’ stem cuttings in spring propagation while inhibiting rooting in the fall. Supplementary lighting from high pressure sodium lamps (HPS) for 16 hr daily had similar effects as CO2 mist in the spring and inhibited root growth in fall propagation. There was a positive interaction between CO2 mist and HPS in spring propagation, suggesting that the promotive effects of these variables were due to enhanced photosynthesis.
Clematis × ‘Jackmanii’ (C. lanuginosa × C. viticella × C. × eriostemon) and Clematis × ‘Comtesse de Bouchard’ (cultivar of C. × ‘Jackmanii’) were evaluated for winter flowering with supplementary lighting treatments combining two photoperiods and two levels of irradiance during September to January. The dormancy of ‘Jackmanii’ was overcome by long (16 hr) days or by high (HPS) irradiance during natural photoperiods (8.5-12 hr); the dormancy of ‘Comtesse de Bouchard’ was overcome only by long days, irradiance having no effect. Terminal flower bud formation was affected similarly by supplementary lighting. The development of lateral flower buds of both cultivars was greatly enhanced by combining long photoperiods and high irradiance.
Long English cucumber (Cucumis sativus L.) plants were treated with one of three nutrient concentrations in combination with two fruit thinning treatments forming a 3 × 2 factorial greenhouse experiment. High nutrient concentration enhanced fruit color at harvest and prolonged shelf life but reduced marketable fruit per plant. Thinning of one-third of the fruit from the main stem and laterals had a similar effect. Cucumbers harvested from the upper canopy generally had longer shelf life than those from the lower canopy. Shelf life was correlated with fruit color at harvest.
The importance of light intensity and spectral quality on fruit color and shelf life of long English cucumber (Cucumis sativus L.) was studied in four greenhouse experiments. The intensity of cucumber greenness was measured nondestructively by video imaging, and shelf life was measured by visual observation of incipient yellowing. In the summer, filters were used to cover individual fruit to reduce light intensity reaching the fruit surface. The lower the light intensity incident on a cucumber, the shorter its shelf life. The average shelf life was 8, 5, or 1 days for cucumbers receiving 100%, 66%, or 31% of natural daylight, respectively. The fruit that were covered with a filter transmitting red (R) light were greener (low grey level via video imaging) than those with a far-red (FR) filter. In the fall, fruit receiving spectral R lighting from fluorescence tubes were greener and had a longer shelf life than those receiving FR lighting from incandescent bulbs. In the winter, high-pressure sodium (HPS) lighting was necessary to supplement natural daylight for crop growth and production. Under HPS, R and FR lighting produced the same fruit greenness and shelf life. In the spring, R-lighted fruit had longer shelf life than FR-lighted ones, although fruit color at harvest was similar. In these four experiments, postharvest shelf life of long English cucumber was generally related to fruit greenness upon harvest. The data suggest the importance of an open canopy in improving fruit greenness and shelf life of greenhouse-grown cucumbers.
Variation in shelf life of greenhouse-grown `Mustang' cucumber (Cucumis sativus L.) fruit was enhanced by preharvest experimental treatments of fruit thinning and fruit shading. Treatments also affected the dynamics of fruit elongation, fruit color at harvest, and chlorophyll fluorescence of the pericarp. Fruit color (grey level) at harvest, as measured by image analysis, had the highest simple (positive) correlation with shelf life. Rapid elongation and high photochemical quenching of fluorescence also characterized fruit having longer shelf life. The ability to predict cucumber yellowing is improved using a multiple regression approach, but prediction achieved by the best subset model is still too low to segregate commercially fruit having a short shelf life.
Alstroemeria plants were grown under 10, 12, 14, 16, 18, and 24 hour photoperiods by employing an 8-hour natural day and low intensity incandescent lighting as a daylength extension. The production of flower stems was increased to a maximal level by extending the photoperiod to 16 hours in ‘Orchid’ and in ‘Regina’. Under 16 hours high-intensity supplementary lighting with high-pressure sodium (HPS) lamps, the production of flower stems in ‘Orchid’ increased by 49% in the first year and 36% in the 2nd year. ‘Regina’ flower stems increased by 26% in the first year and 16% in the 2nd year. HPS lighting increased the number of flowering shoots per square meter from 166 (control) to 262 in ‘Orchid’ and from 10 to 21 in ‘Regina’ during the period November to February.
Lilium longiflorum Thunb. cv. Nellie White bulbs were shipped in 1969, 1970, and 1971 from the west coast to St. Paul by air freight from July to October at 15 day intervals. Bulbs were given 0 or 2 weeks of 10°C, 15.5°C or 21 °C followed by 0 or 6 weeks of 4.5°C. Two weeks exposure to 10°C enhanced shoot emergence and flowering of late-harvested non-cooled bulbs and enhanced flowering of cooled bulbs. Treatments of 15.5°C or 21°C had little influence on shoot emergence and flowering of non-cooled bulbs and delayed flowering of early harvested cooled bulbs. With time and with increased bulb growth the degree of dormancy (delay of emergence) decreased and degree of maturity (enhancement of early flowering by 4.5°) increased.