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Woei-Jiun Guo, Yu-Zu Lin, and Nean Lee

Phalaenopsis leaves. Thus, the light requirement for maximal photosynthetic ability in ‘TS97’ requires further examination. Daylength also affects photosynthetic capacities in CAM plants. In general, short daylengths promote nocturnal stomata opening and

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Ah-Chiou Lee, Fang-Shin Liao, and Hsiao-Feng Lo

daylength, and the number of DMMY so that growers can predict the number of days to grow for MMY. This will also assist growers in choosing appropriate cultivars according to climatic conditions. Materials and Methods Plant materials and cultural practices

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Kenneth E. Cockshull and Anton M. Kofranek

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.

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Yi-Lu Jiang, Yuan-Yin Liao, Meng-Tzu Lin, and Wen-Ju Yang

critical daylength of red pitaya was reported to be ≈12 h, and the two switches between inductive and noninductive periods for red pitaya occur at the vernal and autumnal equinoxes, respectively ( Jiang et al., 2012 ). Southern Taiwan is located in the

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Amir Rezazadeh and Eric T. Stafne

−1 ) with a constant relative humidity of 70%. Another group of cuttings was maintained in a greenhouse with ambient sunlight, average daylength of 10.5–13 h from starting experiment until termination [8 Dec. 2017 to 4 May 2018 (average = 12 h)], and

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Brigitte D. Crawford, John M. Dole, and Ben A. Bergmann

to examine the linear relationship between each parameter and daylength or midday instantaneous light experienced by stock plants before fall and spring greenhouse rooting trials. All statistical analyses were performed using SAS statistical software

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Cary G. Patterson, Douglas D. Archbold, J.G. Rodriguez, and Thomas R. Hamilton-Kemp

The influence of long and short daylengths on twospotted spider mite (TSSM) (Tetranychus urticae Koch) resistance of strawberry (Fragaria ×ananassa Duch.) foliage was studied. Photoperiods of 8 hours (short daylength) and continuous light (long daylength) altered the seasonal change in susceptibility of `Redchief' strawberry foliage to TSSM. Plants exposed to continuous light rapidly became resistant, those exposed to short daylength remained relatively susceptible, and plants under natural daylength exhibited the seasonal change of slowly increasing resistance. Plants resistant to TSSM under long daylength became susceptible 19 days after being switched to a short daylength. Plants that were switched from short to long daylength changed from TSSM susceptible to resistant. Field-grown plants of `Redchief', a short-day sensitive cultivar, and `Tribute', a day-neutral cultivar, exhibited increasing resistance to TSSM from 2 weeks before bloom until 2 weeks into harvest when greatest resistance was observed. These results suggest that TSSM resistance in strawberry is influenced by daylength and that this effect may be independent of daylength effects on strawberry reproductive development.

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Rebecca L. Darnell

Containerized `Climax' and `Beckyblue' rabbiteye blueberry plants (Vaccinium ashei Reade) were exposed to 5 weeks of natural daylengths or shortened daylengths starting 30 Sept. `Beckyblue' plants exposed to short daylengths in the fall initiated more flower buds and had a shorter, more concentrated bloom period than did plants exposed to natural fall daylengths. Reproductive development of `Climax' was not influenced by photoperiod treatments. Leaf carbon assimilation of both cultivars increased under short days. Partitioning of translocated 14C-labeled assimilates to stem tissue increased under short photoperiods for `Beckyblue'; however, partitioning patterns in `Climax' were not affected. Increased carbon fixation and increased partitioning of carbon to stem tissue under short days may contribute to the observed effect of short days on enhancing reproductive development in `Beckyblue'.

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Mary Lewnes Albrecht and Jerald T. Lehmann

Greenhouse- and field-produced plants of Asclepias tuberosa L., butterfly flower, were forced in the greenhouse under various daylengths to produce flowering plants for the florist industry. Examined were post-production cold storage temperature (4.5 and 10C) and period (12, 14, and 16 weeks), forcing daylength (9, 13, 15, or 17 hours), plant-production scheme (greenhouse- vs. field-produced), and planting depth (exposed crowns or crowns planted 1.3 cm below the medium surface). When forced under a 9-hour daylength, blind shoots and aborted flower buds were prevalent. When daylengths exceeded 13 hours, using night interruption, the time to produce a marketable plant was reduced from 71 days to 61 days for 18-month-old greenhouse-produced plants. Daylength of 17 hours delayed flowering of field-produced liners by 15 days in comparison to those forced under 13-hour daylength. Greenhouse-produced plants stored at 10C did not sprout when brought into the forcing greenhouse held at 17/25C (night/day). Field-produced plants, when greenhouse-forced, had fewer flowers per inflorescence (88 to 94 flowers) than greenhouse-produced plants (79 to 87 flowers).

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Jeffrey G. Norcini, Judith M. McDowell, and James H. Aldrich

Profitability and production of hanging baskets of bougainvillea, a short day species, could increase if vegetative growth and flowering were more easily controlled. Three-month-old rooted liners of Bougainvillea `Barbara Karst' and `Rainbow Gold' were transplanted into 4.5-liter hanging baskets (3 liners/basket) in late April (Expt. 1) or late July 1991 (Expt. 2) and pruned 2 or 3 days later. Selected combinations of 0, 600, 800, 1200, or 1600 ppm dikegulac were applied at 0, 2, and 4 weeks after initial pruning. Control plants were also pruned at 4 weeks. Plants were grown under full sun. Peak flowering occurred 9 to 10 weeks after initial pruning in both experiments. Dikegulac enhanced flowering of both cultivars under increasing and decreasing daylengths but was greatest under increasing daylengths, especially for `Rainbow Gold'. There was little to no effect on branching.