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The use of light quality as an alternate method for controlling ornamental plant growth was evaluated using copper sulfate solutions as optical filters, The light passed through CuSO4 solutions had high red/far-red (R/FR) ratio. Plant height and average internode length were significantly reduced by high R/FR light. Plants grown under high R/FR light had smaller leaves and a lower total leaf area but had thicker leaves, as indicated by specific leaf weight, than the control plants. Fresh and dry weights of leaves, stems and roots were reduced by high R/FR light. Dry matter accumulation in leaves was increased by high R/FR light while it was reduced in stems. Exogenous gibberellic acid (GA) application partially overcame the height reduction under high R/FR light indicating that GA biosynthesis maybe affected by light treatment. Results suggests alteration of light quality could be used in controlling ornamental plant growth as an alternate method to conventional chemical growth regulator applications.

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as low as 2−6 mol·m −2 ·d −1 as a result of reductions of outdoor DLIs by up to 60% ( Korczynski et al., 2002 ; Lopez and Runkle, 2008 ). Light impacts growth, morphology, and quality of seedlings ( Graper and Healy, 1991 ; Oh et al., 2010

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Abstract

F. benjamina L. were produced in a greenhouse shaded to provide a maximum natural light level of 400 or 800 μmol s-1m-2 photosynthetic photon flux density (PPFD) for 5 months. Plants were held indoors for 12 weeks under incandescent (INC) or cool-white fluorescent (CWF) lamps at 10 μmol s-1m-2 or 20 μmol s-1m-2 for 12 hr/day. Leaf drop was substantially reduced and plant quality was increased when plants were produced under 800 μmol s-1m-2 or when plants were held indoors under 20 μmol s-1m-2 of light. Leaf loss in response to production light levels, postproduction light levels, and light source was different when measured over time. Dry weight was increased when plants were produced under 800 μmol s-1m-2. Chlorophyll content was increased in plants grown under 400 μmol s-1m-2 or held under CWF lamps.

Open Access

Variation in light quality is known to modify plant morphology, growth, and chemical constituency in plants. In the present study, the effect of light quality on growth and essential oil composition in rosemary (Rosmarinus officinalis L.) was investigated by comparing plants receiving supplemental red (660 nm) and far-red (730 nm) with each other and with control plants not receiving supplemental light. Except for the supplemental light treatments, all plants were grown under natural light conditions in a greenhouse and received full daylight, averaging 9.23 h/day during the study. The red and far-red light treatments, given as day extensions, started daily 15 min before sunset and continued for 4 h each evening for 4 weeks. No significant differences were observed in biomass yield from the different light treatments, but far-red light caused elongation of internodes and a reduction in the number of leaves in comparison with control and red-light treated plants. Essential oil production was highest in plants grown under far-red light treatments.

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Abstract

This study evaluates light quality and photoperiodic effects on vegetative growth on Cucurbita maxima Duch. In a growth chamber with fluorescent and incandescent lighting the quality of light prior to the dark period, rather than photoperiod, significantly affected internode elongation, and end-of-day red (R) and far-red (FR) treatments demonstrated phytochrome involvement. Internode elongation occurred primarily during the dark period. FR treatments at the beginning of the dark period were most promotive, but FR up to 12 hour into a 16 hour dark period promoted internode elongation significantly. Changes in the ratio of R to FR light at sunset are probably not of sufficient duration and intensity to elicit an end-of-day growth response. In the field, changes in light quality at sunset did not alter the growth habit of the bush or bush-vine phenotypes.

Open Access

Storage systems for tissue-cultured plants offer versatility in managing labor to meet market availability. Storage systems that minimize growth and yet sustain photosynthetic and regrowth potential require temperature, light quality, and light intensity to be manipulated for plantlet quality during and after storage. Broccoli (Brassica oleracea L. Botrytis Group `Green Duke') plantlets were cultured photoautotrophically (without sugar) or photomixotrophically (with sugar) on cellulose plugs in liquid medium in vitro for 3 weeks at 23°C and 150 μmol·m–2·s–1 photosynthetic photon flux (PPF). To determine the conditions that yield a zero carbon balance, plantlets were subsequently stored for 3 days under different temperatures (1°C, 5°C, 10°C, 15°C), different light intensities (1.6 PPF, 4.1 PPF, 8.6 PPF), and different light spectra (white, blue, red). Plantlets stored under 5 PPF and 5°C maintained a zero carbon balance. Subsequently, plantlets were stored for 4, 8, or 12 weeks at 5°C under darkness or 5 PPF of white, red or blue light. Stem elongation was observed for plantlets stored under blue light. Plantlets stored under red light were characterized by increased chlorophyll, increased specific leaf mass (leaf dry mass per unit leaf area, SLM), increased starch in leaf tissue, and increased total soluble sugars in leaf and stem tissue. Plantlets grown with sucrose were characterized by increased dry mass, regardless of light treatment. After 8 weeks, plantlets grown with or without sucrose and stored in darkness did not survive acclimatization to greenhouse.

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Abstract

Highest quality Dracaena angustifolia ‘Honoriae’, were produced under 26 klx at all fertilizer levels and 52 klx at 12 or 16 g Osmocote 18N-3P-10K/20 cm diameter pot for 4 months. After 7 months under an interior environment, plants that received 78 klx in the production area and held under 1 klx interior light dropped more than twice the number of leaves as the other plants. Several interactions of light and fertilizer levels are discussed.

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Abstract

The effect of light quality during seed development and drying on subsequent germination was investigated in watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] with ‘Sugar Baby’ and 2 dwarf strains, WB-2 and ‘Sugar Baby’ (dw-2). The light treatments during seed drying, fluorescent (F), incandescent (Inc), red (R), and far-red (FR), did not consistently affect percent germination. Seeds dried under R or F light usually germinated faster than those dried in darkness or under FR light, but the effect was too small to justify application in commercial seed processing. Seeds from fruit covered with black polyethylene during development germinated faster and were less sensitive to light treatments during drying than seeds from uncovered fruit.

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Abstract

In the paper, Influence of Photoperiod and Light Quality on Stolon Formation and Flowering of Chlorophytum comosum (Thunb.) Jacques by R. D. Heins and H. F. Wilkins (J. Amer. Soc. Hort. Sci. 103(5):687-689. 1978), the authors names were inadvertently omitted from the table of contents.

Open Access

Young watermelon (Citrullus lanatus cv. Sugar Baby) plants were treated with end-of-day (EOD) Red (R), Far-red (FR), and Far-red followed by Red (FR/R) light for 15 minutes. Control plants had no EOD light treatment. FR light treatments influenced plant growth and development (i.e., petiole elongation, internode elongation, and reduced petiole angles). Plants were sampled every 4 hours for a 24 hour period from each light treatment. Tissues (petioles, leaves, stems, and cotyledons) were analyzed from each treatment and sampling time combination for soluble carbohydrate and starch concentrations. Results suggested that carbohydrate concentration, distribution, and diurnal fluctuation were affected by EOD light quality treatments. Petioles of FR treated plants contained the greatest concentration of glucose, fructose and total soluble carbohydrates, and the least concentration of stachyose and starch. Stems of FR treated plants had the least concentration of total sugars and starch. Petioles of R treated plants contained the greatest concentration of stachyose and the least concentration of glucose. The changes in concentration of the storage carbohydrate (starch) and breakdown products (fructose and glucose) of the translocated sugar (sucrose) may be correlated to active growth of petioles and stems in response to light quality.

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