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effects of postharvest handling and environments on potted poinsettia performance have become better understood over the past few decades. Light levels are often quite low in postproduction environments: generally brightest in supermarkets, lower in home

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Schefflera arboricola is a member of the family Araliaceae and one of the most popular foliage plants used to landscape interiors. Generally, low light intensities, typical for indoors, increase leaf drop and reduce leaf quality ( Conover and

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usefulness at relatively low-light locations such as those of the southeastern United States merits assessment. The relatively low-light environment of the southeastern United States exhibits considerable cloud cover and atmospheric water vapor (i

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fixation ( Maxwell and Johnson, 2000 ). On the other hand, during orchid production in Taiwan, short-term, low-light conditions often occur as a result of afternoon showers in the summers, which in turn complicate the greenhouse management for maximal light

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Photosynthetic light harvesting was investigated under low-light stress conditions relevant to the problem of interior longevity of potted ornamental plants. Comparisons of leaf pigment levels and chlorophyll fluorescence excitation spectra were made for `Gutbier V-10 Amy' poinsettia (Euphorbia pulcherrima Willd.), which has poor interior longevity, and `Eckespoint Lilo' poinsettia, which has superior interior longevity. The results show that `Eckespoint Lilo' had higher total chlorophyll content per leaf area and lower chlorophyll a: chlorophyll b ratio than `Gutbier V-10 Amy'. In low-light stress, `Eckespoint Lilo' retained its chlorophyll or even accumulated higher levels than in high light, while `Gutbier V-10 Amy' did not exhibit higher chlorophyll retention in low light. Both cultivars acclimatized to low-light stress by decreasing the chlorophyll a: chlorophyll b ratio, and this acclimatization was evident sooner in younger, outer-canopy leaves above the pinch than in older leaves below the pinch. Both cultivars also increased the chlorophyll: carotenoid ratio in low light. These changes in pigment composition, which were essentially structural changes, were reflected in functional changes in light harvesting, as assessed by measurements of chlorophyll fluorescence excitation spectra.

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Broccoli (Brassica oleracea L. Botrytis Group `Green Duke') and Hosta tokudama F. Maekawa `Newberry Gold' plantlets, which were ready for transplanting after photoautotrophic (sugar-free) culture, were stored 4 to 6 weeks at 5C under various light qualities and photosynthetic photon fluxes (PPF). Illumination during storage maintained quality, photosynthetic ability, and regrowth potential of plantlets stored at low temperature. PPF affected quality of broccoli and Hosta plantlets. Broccoli plantlets responded to storage light quality, while Hosta did not. White light maintained the quality of broccoli plantlets better during 6 weeks of storage than did red or blue light. Red and blue light caused an increase in internode length and reduction in chlorophyll concentrations compared to white light. Photosynthetic and regrowth potentials of plantlets were not affected by spectral quality during storage. Considering changes in dry weight, stem length, and leaf yellowing, the quality of broccoli plantlets was best maintained under white light at 2 μmol·m–2·s–1 PPF. PPF and light quality were shown to be important factors in the preservation of transplant quality and suppression of growth of the plantlets during low-temperature storage.

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( Craver et al. 2019 ), root dry mass (RDM), and shoot dry mass ( Oh et al. 2010 ; Poel and Runkle 2017a ) also decrease. Increasing the DLI when natural light is low requires the use of supplemental lighting, but the costs of supplemental lighting can be

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Abstract

Exposure to constant 7.2°C temperature and 540 lux incandescent light for 6 weeks induced flowering in rooted cuttings of ‘Lavender Grand Slam’ pelargonium in small peat or clay pots. Total production time from the beginning of propagation to full bloom with this method of flower induction is 15 to 18 weeks. Artificially-imposed low-temperature treatment makes it feasible to grow pelargoniums as a flowering pot plant on a year-around basis.

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High temperatures during flowering frequently limit yields of some bell pepper cultivars in New York fields. Previous research has shown that subjecting the plants to low light at flowering can have similar effects. To determine if cultivar differences in flower abscission and yield could be accentuated by such a shade stress, field plots of six cultivars were subjected to 1 week of low light during flowering. Shade cloth tunnels were erected over the plant rows in two experiments, reducing incident light by 80%. Nondestructive abscission counts were taken at the start, and 7 days after the end of a 7-day shade period. Mature green fruit were harvested periodically. Low light stress resulted in 68% and 86% abscission at the first three fruiting nodes in 1992 and 1994, respectively. Cultivars showed differential abscission in unshaded plots, and after shade, producing a significant cultivar: shade interaction. `Ace' showed least abscission and maintained yields with shading; `Camelot' lost nearly all flowers and buds with low light stress, and was reduced by 75% and 91% in marketable yield in 1992 and 1994, respectively. Results indicate that shade stress accentuates abscission susceptibility in bell pepper cultivars. Pepper lines selected for low light tolerance may show promise in resisting flower abscission at high temperature.

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Abstract

Potted foliage and floricultural species were evaluated for transpiration rates under low-light conditions. Environmental conditions during the experiment were 25° ± 2°C, 75% ± 10% RH, and 20 μmol·s−1 ·m−2 (400−700 nm) light intensity. Leaf cuticular and stomatal morphology were characterized with scanning electron micrographs. Coleus had the highest transpiration rate, Chrysanthemum was intermediate, and Ficus, Peperomia, and Epipremnum had the lowest transpiration rates. Abscisic acid (ABA) treatment reduced the daytime transpiration, which eliminated the diurnal fluctuation of transpiration in all species but had no effect on night transpiration, except in Coleus. Assuming complete stomatal closure at night with ABA treatment, cuticular transpiration accounts for 43% to 80% of the total transpiration rate under low-light conditions. This result points to the importance of leaf cuticular and stomatal characteristics in controlling water use of plants under low light or dark-storage. Species differed in cuticular characteristics, stomatal frequency and size, and leaf area. Stomatal frequency correlated well with transpiration rates, except in those species with unique stomatal morphologies, such as Ficus, with sunken stomates surrounded by a protruding ridge. Coleus and Chrysanthemum developed less epicuticular wax than the other species. Epicuticular and stomatal characteristics were correlated with transpiration rates of these species.

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