A high daily light integral can influence photoperiodic flowering responses in long day herbaceous ornamentals

Flowering and morphology of four Petunia Juss. spp. [P. axillaris (Lam.) Britton et al., P. exserta Stehmann, P. integrifolia (Hook.) Schinz & Thell., and P. ×hybrida Vilm.] were evaluated in response to photoperiod and temperature. Photoperiod responses were evaluated under 9-h short days (SD), 9-h photoperiod plus 4-h night-interruption lighting (NI), or a 16-h photoperiod supplemented with high-pressure sodium lamps (16-h HPS). All species flowered earlier under NI than SD and were classified as facultative (quantitative) long-day plants. Increasing the daily light integral within long-day treatments increased flower bud number for P. axillaris only. In a second experiment, crop timing and quality were evaluated in the temperature range of 14 to 26 °C under 16-h HPS. The rate of progress toward flowering for each species increased as temperature increased from 14 to 26 °C, suggesting the optimal temperature for development is at least 26 °C. The calculated base temperature for progress to flowering varied from 0.1 °C for P. exserta to 5.3 °C for P. integrifolia. Flowering of P. axillaris and P. integrifolia was delayed developmentally (i.e., increased node number below the first flower) at 14 °C and 17 °C or less, respectively, compared with higher temperatures. Petunia axillaris and P. integrifolia flower bud numbers decreased as temperature increased, whereas P. ×hybrida flower bud number was similar at all temperatures. The differences in crop timing and quality traits observed for these species suggest that they may be useful sources of variability for petunia breeding programs.

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Comparing Flowering Responses of Long-day Plants under Incandescent and Two Commercial Light-emitting Diode Lamps

HortTechnology ◽

10.21273/horttech.24.4.490 ◽

2014 ◽

Vol 24 (4) ◽

pp. 490-495 ◽

Cited By ~ 16

Author(s):

Fumiko Kohyama ◽

Catherine Whitman ◽

Erik S. Runkle

Keyword(s):

Plant Height ◽

Energy Efficient ◽

Light Emitting Diode ◽

Node Number ◽

Light Emitting ◽

Daily Light Integral ◽

Low Intensity ◽

Long Day ◽

Long Day Plants ◽

Light Integral

When the natural daylength is short, commercial growers of ornamental long-day plants (LDP) often provide low-intensity lighting to more rapidly and uniformly induce flowering. Incandescent (INC) lamps have been traditionally used for photoperiodic lighting because their spectrum, rich in red [R (600 to 700 nm)] and far-red [FR (700 to 800 nm)] light, is effective and they are inexpensive to purchase and install. Light-emitting diodes (LEDs) are much more energy efficient, can emit wavelengths of light that specifically regulate flowering, and last at least 20 times longer. We investigated the efficacy of two new commercial LED products developed for flowering applications on the LDP ageratum (Ageratum houstonianum), calibrachoa (Calibrachoa ×hybrida), two cultivars of dianthus (Dianthus chinensis), and two cultivars of petunia (Petunia ×hybrida). Plants were grown under a 9-hour short day without or with a 4-hour night interruption (NI) delivered by one of three lamp types: INC lamps (R:FR = 0.59), LED lamps with R and white (W) diodes [R + W (R:FR = 53.35)], and LED lamps with R, W, and FR diodes [R + W + FR (R:FR = 0.67)]. The experiment was performed twice, both at a constant 20 °C, but the photosynthetic daily light integral (DLI) during the second replicate (Rep. II) was twice that in the first (Rep. I). In all crops and in both experimental replicates, time to flower, flower or inflorescence and node number, and plant height were similar under the R + W + FR LEDs and the INC lamps. However, in Rep. I, both petunia cultivars developed more nodes and flowering was delayed under the R + W LEDs compared with the INC or R + W + FR LEDs. In Rep. II, petunia flowering time and node number were similar under the three NI treatments. Plant height of both dianthus cultivars was generally shorter under the NI treatment without FR light (R + W LEDs). These results indicate that when the DLI is low (e.g., ≤6 mol·m−2·d−1), FR light is required in NI lighting for the most rapid flowering of some but not all LDP; under a higher DLI, the flowering response to FR light in NI lighting is apparently diminished.

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Promotion of Flowering from Far-red Radiation Depends on the Photosynthetic Daily Light Integral

HortScience ◽

10.21273/hortsci12544-17 ◽

2018 ◽

Vol 53 (4) ◽

pp. 465-471 ◽

Cited By ~ 3

Author(s):

W. Garrett Owen ◽

Qingwu Meng ◽

Roberto G. Lopez

Keyword(s):

Plant Height ◽

Open Flower ◽

Led Lighting ◽

Daily Light Integral ◽

Low Intensity ◽

Short Day ◽

Long Day ◽

Long Day Plants ◽

African Marigold ◽

Light Integral

Under natural short days, growers can use photoperiodic lighting to promote flowering of long-day plants and inhibit flowering of short-day plants. Unlike traditional lamps used for photoperiodic lighting, low-intensity light-emitting diode (LED) lamps allow for a wide array of adjustable spectral distributions relevant to regulation of flowering, including red (R) and white (W) radiation with or without far-red (FR) radiation. Our objective was to quantify how day-extension (DE) photoperiodic lighting from two commercially available low-intensity LED lamps emitting R + W or R + W + FR radiation interacted with daily light integral (DLI) to influence stem elongation and flowering of several ornamental species. Long-day plants [petunia (Petunia ×hybrida Vilm.-Andr. ‘Dreams Midnight’) and snapdragon (Antirrhinum majus L. ‘Oh Snap Pink’)], short-day plants [african marigold (Tagetes erecta L. ‘Moonsong Deep Orange’) and potted sunflower (Helianthus annuus L. ‘Pacino Gold’)], and day-neutral plants [pansy (Viola ×wittrockiana Gams. ‘Matrix Yellow’) and zinnia (Zinnia elegans Jacq. ‘Magellan Cherry’)] were grown at 20/18 °C day/night air temperatures and under low (6–9 mol·m−2·d−1) or high (16–19 mol·m−2·d−1) seasonal photosynthetic DLIs from ambient solar radiation combined with supplemental high-pressure sodium lighting and DE LED lighting. Photoperiods consisted of a truncated 9-hour day (0800–1700 hr) with additional 1-hour (1700–1800 hr, 10 hours total), 4-hour (1700–2100 hr, 13 hours total), or 7-hour (1700–2400 hr, 16 hours total) R + W or R + W + FR LED lighting at 2 μmol·m−2·s−1. Days to visible bud, plant height at first open flower, and time to first open flower (TTF) of each species were influenced by DLI, lamp type, and photoperiod though to different magnitudes. For example, plant height of african marigold and potted sunflower at first open flower was greatest under R + W + FR lamps, high DLIs, and 16-hour photoperiods. Petunia grown under R + W lamps, high DLI, and 10- and 13-hour photoperiods were the most compact. For all species, TTF was generally reduced under high DLIs. For example, regardless of the lamp type, flowering of african marigold occurred fastest under a high DLI and 10-hour photoperiod. Flowering of petunia and snapdragon occurred fastest under a high DLI, R + W + FR lamps, and a 16-hour photoperiod. However, only under high DLIs, R + W or R + W + FR lamps were equally effective at promoting flowering when used to provide DE lighting. Our data suggest that under low DLIs, flowering of long-day plants (petunia and snapdragon) occurs more rapidly under lamps providing R + W + FR, whereas under high DLIs, flowering is promoted similarly under either R + W or R + W + FR lamps.

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Daily Light Integral Influences Steviol Glycoside Biosynthesis and Relative Abundance of Specific Glycosides in Stevia

HortScience ◽

10.21273/hortsci.50.10.1479 ◽

2015 ◽

Vol 50 (10) ◽

pp. 1479-1485 ◽

Cited By ~ 7

Author(s):

Jennifer M. Evans ◽

Veronica A. Vallejo ◽

Randolph M. Beaudry ◽

Ryan M. Warner

Keyword(s):

Solar Radiation ◽

Stevia Rebaudiana ◽

Steviol Glycosides ◽

Rebaudioside A ◽

Daily Light Integral ◽

Steviol Glycoside ◽

Long Day ◽

Genetic And Environmental Factors ◽

Rebaudioside D ◽

Light Integral

The biosynthesis of steviol glycosides is affected by both genetic and environmental factors. To evaluate the influence of total daily solar radiation or daily light integral (DLI) under long-day conditions on steviol glycoside concentration, we grew Stevia rebaudiana under ambient irradiance or varying levels of shading at different times of the year in both greenhouse and field environments, resulting in DLIs ranging from 3.55 to 20.31 mol·m−2·d−1 in the greenhouse and 10.32 to 39.7 mol·m−2·d−1 in the field. Total steviol glycoside concentration of selected leaves from greenhouse-grown plants increased as DLI increased up to ca. 10 mol·m−2·d−1, remaining constant with further increases in DLI, and was similar across the range of DLIs evaluated in the field. DLI influenced both the concentration and the relative proportions of specific steviol glycosides. Rebaudioside A concentration increased as DLI increased from 3.55 to 8.53 mol·m−2·d−1, remaining similar with further increases in DLI. Rebaudioside D and stevioside concentration of selected leaves from field-grown plants decreased by 22% and 13%, respectively, as DLI increased from 10.32 to 39.7 mol·m−2·d−1, while rebaudioside A and M concentrations remained similar across this DLI range. Collectively, these results indicate that the greatest influence of DLI on steviol glycoside concentration occurs under relatively low DLIs (<10 mol·m−2·d−1). However, higher DLIs can significantly affect the synthesis of minor glycosides of increasing commercial importance including rebaudioside D.

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Daily Light Integral, Prevernalization Photoperiod, and Vernalization Temperature and Duration Control Flowering of Easter Cactus

HortScience ◽

10.21273/hortsci.42.7.1596 ◽

2007 ◽

Vol 42 (7) ◽

pp. 1596-1604 ◽

Cited By ~ 2

Author(s):

Charles L. Rohwer ◽

Royal D. Heins

Keyword(s):

Daily Light Integral ◽

Short Day ◽

Long Day ◽

Light Integral

Experiments were performed on Hatiora gaertneri (Regel) Barthlott ‘Jan’ and ‘Rood’ and H. ×graeseri (Wedermann) Barthlott ‘Evita’ to determine their flowering responses to 1) daily light integral (DLI) before and during vernalization; 2) 0 to 6 weeks of short-day (SD) or long-day (LD) photoperiods before vernalization at 10, 12.5, or 15 °C; 3) propagation from April to July; 4) timing of leveling before or during inductive treatments; and 5) SD photoperiods before vernalization under darkness at 0 to 10 °C. ‘Jan’ grown under elevated DLI before vernalization and low DLI during vernalization flowered more prolifically than plants grown under low DLI before vernalization or high DLI during vernalization at 15 °C. Six weeks of SD photoperiods before vernalization increased the number of buds per flowering phylloclade after vernalization at 10 °C and increased flowering uniformity when vernalization duration was insufficient at 10 °C or vernalization temperature was 12.5 or 15 °C. For plants flowering in January, propagation the previous April produced better flowering than propagation in May, June, or July. Removal of apical phylloclades during prevernalization SD or during vernalization was deleterious to flowering. Vernalization in the dark produced marginal flowering, but SD treatment before vernalization increased the percentage of apical phylloclades flowering, buds per flowering apical phylloclade, and percentage of plants flowering after dark vernalization. ‘Evita’ flowered more poorly than either ‘Jan’ or ‘Rood’. Collectively, the most uniform flowering in January occurred when plants were exposed to a sequence of 4 to 6 weeks of SD, vernalization at 7.5 to 15 °C for 8 weeks, then growth under LD for 7 weeks.

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Daily light integral requirements of warm‐season turfgrasses for golf course fairways and investigating in situ evaluation methodology

Crop Science ◽

10.1002/csc2.20234 ◽

2020 ◽

Vol 60 (6) ◽

pp. 3301-3313

Author(s):

Travis R. Russell ◽

Douglas E. Karcher ◽

Michael D. Richardson

Keyword(s):

Warm Season ◽

Evaluation Methodology ◽

Golf Course ◽

Daily Light Integral ◽

Light Integral

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Conserved Expression Profiles of Circadian Clock-related Genes in Two Lemna Species Showing Long-day and Short-day Photoperiodic Flowering Responses

Plant and Cell Physiology ◽

10.1093/pcp/pcj027 ◽

2006 ◽

Vol 47 (5) ◽

pp. 601-612 ◽

Cited By ~ 48

Author(s):

Kumiko Miwa ◽

Masayuki Serikawa ◽

Sayaka Suzuki ◽

Takao Kondo ◽

Tokitaka Oyama

Keyword(s):

Circadian Clock ◽

Expression Profiles ◽

Short Day ◽

Photoperiodic Flowering ◽

Long Day

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Effects of Daily Light Integral and LED Spectrum on Growth and Nutritional Quality of Hydroponic Spinach

Agronomy ◽

10.3390/agronomy10081082 ◽

2020 ◽

Vol 10 (8) ◽

pp. 1082 ◽

Cited By ~ 1

Author(s):

Wei Gao ◽

Dongxian He ◽

Fang Ji ◽

Sen Zhang ◽

Jianfeng Zheng

Keyword(s):

Vitamin C ◽

Blue Light ◽

Nutritional Quality ◽

Red Light ◽

Nitrate Content ◽

Energy Yield ◽

Daily Light Integral ◽

Fluorescent Lamps ◽

Plant Factory ◽

Light Integral

To achieve clean and high-quality spinach production, the effects of daily light integral (DLI) and light spectrum on growth, nutritional quality, and energy yield of hydroponic spinach (Spinacia oleracea L.) were investigated in a closed plant factory under light-emitting diode (LED) lighting. The hydroponic spinach plants were grown under 16 combinations of four levels of DLI (11.5, 14.4, 17.3, and 20.2 mol m−2 day−1) with four light spectra: LED lamps with ratio of red light to blue light (R:B ratio) of 0.9, 1.2, and 2.2 and fluorescent lamps with R:B ratio of 1.8 as control. The results show that total fresh and dry weights, energy yield, and light energy use efficiency (LUE) of harvested spinach were higher under D17.3-L1.2 treatment compared to other treatments. The higher net photosynthetic rates were shown at DLI of 17.3 mol m−2 day−1 regardless of light quality. Higher vitamin C contents of spinach in all LED treatments were obtained compared with the control. L1.2 treatments with higher fraction of blue light led to more vitamin C content, lower nitrate content, and higher LUE independent of DLI. L2.2 treatment with more fraction of red light was beneficial to reduce oxalate accumulation. Power consumption based on increased total fresh weight under LED lamps with R:B ratio of 1.2 in different DLIs was over 38% lower than that under the fluorescent lamps and 1.73 kWh per 100 g FW at DLI of 17.3 mol m−2 day−1. In conclusion, lighting environment in DLI of 17.3 mol m−2 day−1 using LED lamps with R:B ratio of 1.2 is suggested for the design of a LED plant factory for hydroponic spinach production.

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