Effect Of Daily Light Integral Research Articles

Modeling purple basil, sage, spearmint, and sweet basil responses to daily light integral and mean daily temperature.

Mean daily temperature (MDT) and daily light integral (DLI) can interact to influence growth and development of plants. Our objectives were to determine 1) the extent DLI and MDT influence growth and development of purple basil 'Dark Opal' (Ocimum basilicum), sage 'Extrakta' (Salvia officinalis), spearmint 'Spanish' (Mentha spicata), and sweet basil 'Nufar' (Ocimum basilicum) and 2) the influence on purple basil color. Young plants were transplanted into hydroponic systems in five greenhouse compartments with MDT set points of 23, 26, 29, 32, or 35°C and DLIs from 5 to 19 mol·m‒2·d‒1, respectively. At harvest, growth, development, and leaf color was measured. Branch number of all genera increased as MDT increased from ~23 to 35°C. Sweet basil branch number increased as DLI increased from 5.5 to 13.2 mol·m‒2·d‒1, but the effect of DLI was attenuated as MDT decreased. In contrast, increasing DLI from ~5-6 to ~18-19 mol·m‒2·d‒1 increased sage and spearmint branch number more when MDT was lower (~23°C) compared to ~35°C, while branch number of purple basil was not influenced by DLI. The optimal MDT (MDTopt) for sage and spearmint fresh mass decreased from 27.5 to 23.5°C and from 30.4 to 27.8°C, respectively, as DLI increased from 6 to 18 mol·m‒2·d‒1, while sweet basil fresh mass MDTopt increased from 32.6 to 35.5°C as DLI increased from 6 to 11 mol·m‒2·d‒1. Purple basil was greener [hue angle (h°) = 99° to 138°] when MDT was ~35°C regardless of DLI, but when MDT was lower (~25°C), basil was more purple (h° = 335°) at a DLI of 18.7 compared to 5.0 mol·m‒2·d‒1 (h° = 98°). Taken together, MDT and DLI can have a large impact on plant growth, development, and color and can be manipulated to achieve desired characteristics.

Effects of daily light integral and photoperiod with successive harvests on basil yield, morpho-physiological characteristics, and mineral composition in vertical farming

In recent years, vertical farming is becoming increasingly popular for the production of leafy vegetables and aromatic herbs, such as basil (Ocimum basilicum L.). However, research has focused primarily on the effect of light quality levels, quantity, and photoperiod in order to define more energy-efficient basil growing protocols. Although scientists have underlined the positive response of this poliedric aromatic herb to successive harvests, this technique had not been investigated under sole source lighting with crop grown in a vertical farming cultivation. Two experiments were carried out in which the effects of two daily light integrals (DLI, 7.5 and 15 mol m–2 d–1) and three photoperiods (P, 14/10, 16/8, and 18/4 photoperiod/dark period) were evaluated in relation to two successive harvests on Genovese basil. In the first experiment, at the first cut, a DLI of 15 mol m–2 d–1 improved yield, yield parameters, and morphophysiological characteristics, but reduced incident light use efficiency (LUE), compared to a DLI of 7.5 mol m–2 d–1. At the second cut, irrespective of the DLI used, plants grown at the first cut with a DLI of 15 mol m–2 d–1 did not show significant differences in plant fresh biomass. In contrast, for plants grown at the first cut with a DLI of 7.5 mol m–2 d–1, the DLI of 15 mol m–2 d–1 used at the second cut improved yield and photosynthetic performance. Regardless of photoperiod, the cuts increased fresh biomass and DLI by 205.1% (on average), confirming how this pre-harvest factor can be used to achieve desired yield and quality from basil with potentials to enhance LUE and resource savings in the vertical cultivation.

Daily light integral and/or photoperiod during the young plant and finishing stages influence floral initiation and quality of witchgrass and marigold cut flowers.

To produce consistent and high-quality specialty cut flowers throughout the year, growers in temperate climates must utilize controlled environment greenhouses. Research-based information on photoperiod management and supplemental lighting for specialty cut flowers is limiting. Therefore, our objectives were (1) to determine the effect of photoperiod during the young-plant and finishing stages on floral initiation and morphology of witchgrass ‘Frosted Explosion’ (Panicum capillare) and marigold ‘Xochi’ (Tagetes erecta) and (2) to quantify the effect of daily light integral (DLI) on floral initiation and morphology of witchgrass during the finishing stage. Seeds of marigold and multi-seed pellets of witchgrass were sown and placed under 9-, 11- (marigold only), 12-, 13-, 14-, 15-, 16-, 18-, or 24-h photoperiods or a 9-h short day with a 4-h night interruption (NI) from 2200 to 0200 h. Plugs were distributed among 10-, 11-, 12-, 13-, 14-, 15-, or 16-h photoperiods or a 4-h NI, for finishing. Witchgrass was finished under a very low or moderate DLI of ≈3 or 10 mol⋅m–2⋅d–1, respectively, while marigold was finished under a DLI of ≈10 mol⋅m–2⋅d–1. Marigold grown under a photoperiod ≥ 11 h or a 4-h NI during the young-plant stage and finished under an 11- or 12-h photoperiod had thick stems and consistently met the marketable stem length of ≥ 65 cm. Up to 29% and 107% more stems were harvestable under 11- and 12-h finishing photoperiods, respectively, compared to a 10-h finishing photoperiod. Marigold visible buds were delayed, and stems were not harvestable under photoperiods ≥ 13 h or a 4-h NI after 8 weeks. Young witchgrass plants grown under a photoperiod between 14- and 24-h or a 4-h NI and finished under photoperiods ≥ 14 h or a 4-h NI, and at least a moderate DLI, were reliably harvestable (≥ 50 cm long with a fully developed panicle). Witchgrass finished under day lengths < 13 h (rep. 1) or < 14 h (rep. 2) flowered prematurely and were roughly one-sixth the length of harvestable stems at an open flower. All witchgrass stems grown under a very low DLI were shorter and thinner than those grown under a moderate DLI, and none were harvestable. Therefore, we recommend growing marigold ‘Xochi’ young plants under a photoperiod ≥ 11 h or a 4-h NI and finishing under a 12-h photoperiod. Additionally, witchgrass ‘Frosted Explosion’ young plants should be grown under a photoperiod ≥ 14 h or a 4-h NI and finished under photoperiods ≥ 14 h or a 4-h NI to prevent premature flowering. Witchgrass and marigold cut flowers should be finished under a DLI of ≥ 10 mol⋅m–2⋅d–1 for consistent production of high-quality stems.

Effects of daily light integral on growth and nitrate content of basil grown for indoor gardening

Effects of daily light integral on growth and nitrate content of basil grown for indoor gardening

Effects of daily light integral on tomato (Solanum lycopersicon L.) grafting and quality in a controlled environment

Effects of daily light integral on tomato (Solanum lycopersicon L.) grafting and quality in a controlled environment

The Effect of Daily Light Integral, Ethephon, and Node Position of Impatiens ×hybrida Stock Plants on Flowering of the Harvested Unrooted Cuttings

Herbaceous stock plant production and cutting harvest methods affect the performance of cuttings harvested from those stock plants. Specifically, the effect of daily light integral (DLI), ethephon spray applications, and the stock plant node position (NPSP) of hybrid impatiens (Impatiens ×hybrida) ‘Compact Electric Orange’ stock plants on the flowering of the harvested cuttings was examined. The DLI treatments were grouped in ranges of low (5.1–5.5 mol·m–2·d–1), medium (7.6–8.8 mol·m–2·d–1), and high (10.3–12.0 mol·m–2·d–1) levels. The stock plants were treated weekly with 0, 50, 100, 200, or 300 mg·L–1 ethephon. Cuttings were harvested from six NPSP, which refers to the location on the stock plants from which the cuttings were harvested. Time to flower of the harvested cuttings decreased as DLI increased from 5.1 to 12.0 mol·m–2·d–1, as ethephon concentrations decreased from 300 to 0 mg·L–1, and as NPSP moved from lower to upper positions within the stock plant canopy. Time to flower was highly correlated with the node position on the cutting (NPC) where the first flower appeared. For example, when flowers appeared in the lowest NPC on the shoot (NPC 1), the first flower opened 2.5 weeks after sticking the unrooted cuttings in propagation, while flowers that appeared in NPC 7, the seventh-oldest node from the base of the cutting, opened at 9.0 weeks. The results demonstrate how stock plant management practices can be manipulated to produce cuttings that allow growers to produce flowering plants on different schedules, i.e., production time can be shortened from conventional production schedules, which may allow hybrid impatiens to be marketed like bedding plant species such as impatiens (Impatiens walleriana).

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

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.

Growth characteristics and flowering initiation of Phalaenopsis Queen Beer ‘Mantefon’ as affected by the daily light integral

This study was conducted to determine the effects of daily light integral (DLI) levels with different photoperiods and light intensities on the growth and flowering initiation of Phalaenopsis plants. Five-month-old Phalaenopsis Queen Beer ‘Mantefon’ plants were treated with combinations of three photoperiods [8/16 (day/night, short day, SD), 12/12 (medium day, MD), and 16/8 h (long day, LD)] and three light intensities in the range of photosynthetically active radiation of 50, 100, and 200 μmol·m−2·s−1, resulting in DLI levels ranging from 1.44 to 11.52 mol·m−2·d−1 with warm-white LEDs at 28°C during the vegetative period. Additionally, 12-month-old plants were treated with combinations of three photoperiods [8/16 (day/night, SD), 8 + 8/8 (day-extension (DE); an extension with 10 μmol·m−2·s−1 for 8 h right after the SD), and 16/8 h (LD)] and three light intensities (75, 150, and 300 μmol·m−2·s−1), resulting in DLI levels ranging from 2.16 to 17.28 mol·m−2·d−1, at 20°C during the forcing period for flowering. During the vegetative period, plants showed a tendency of overgrowth in leaves, via the formation of long and narrow leaves, as the light intensity decreased, irrespective of the photoperiod. The number of new leaves, total leaf area, and shoot and root dry weights increased with increasing photoperiod and light intensity, implying an increase in the amount of light energy. During the forcing period, photoperiodic effects on flowering initiation were not observed, while increasing the light intensity increased the number of inflorescences and accelerated spiking. The DLI showed higher correlation coefficients with growth and flowering initiation characteristics than those of the photoperiod or light intensity alone. New leaf emergence, biomass accumulation, and spiking were enhanced as DLI levels increased, although these positive effects were gradually saturated. These findings indicated that the DLI is a major factor in the growth and flowering initiation of Phalaenopsis plants and increasing DLI levels can promote growth or flowering initiation of these plants. These findings will be useful in controlling light conditions to maximize the growth rate and shorten the cultivation time in Phalaenopsis cultivation.

Flowering of cyclamen is accelerated by an increase in temperature, photoperiod, and daily light integral

SummaryCyclamen (Cyclamen persicum Mill.) crop production times can be reduced by increasing the greenhouse temperature, but alternative methods to accelerate crop development are desirable when energy costs for heating are high. The effects of photoperiod and increasing daily light integral (DLI) on cyclamen remain unclear. We performed experiments to examine the effect of DLI using two temperatures (16°C or 20°C) and three photoperiods (8, 12, or 16 h) delivering DLI values of 4.9, 7.3, or 9.8 mol m–2 d–1, respectively, and the effect of night interruption (NI) lighting from incandescent lamps (IL), on the flowering of cyclamen ‘Metis Purple Flame’. Plants grown at 20°C reached the visible flower bud (VB) stage earlier than plants grown at 16°C under all photoperiods. NI hastened flower bud initiation by 22 – 29 d compared with an 8-h photoperiod at both temperatures. Plants grown under the 8-h photoperiod with an NI treatment (DLI = 4.9 mol m–2 d–1) flowered at a similar time as plants grown under the 12-h photoperiod (DLI = 7.3 mol m–2 d–1). In addition, plants grown at 16°C with an NI reached the VB stage in a similar time to plants grown at 20°C with an 8-h photoperiod. Therefore, the effects of increasing the DLI, providing NI lighting, or increasing the temperature can be compared, so that growers can determine which strategies can reduce the greenhouse production time of cyclamen most cost-effectively.

DAILY LIGHT INTEGRAL INFLUENCES ROOTING AND QUALITY OF PETUNIA CUTTINGS

DAILY LIGHT INTEGRAL INFLUENCES ROOTING AND QUALITY OF PETUNIA CUTTINGS

The Effect of Daily Light Integral on Floral Initiation of Pelargonium ×domesticum L.H. Bailey

Nine cultivars of Pelargonium ×domesticum L.H. Bailey were evaluated for the effect of daily light integral on floral initiation. Plants were grown at four daily light integrals: 5, 10, 15, or 20 mol·m-2·d-1 for a 16-hour photoperiod in environmental growth chambers at constant 15.5 °C. Meristems were examined at 50 mol·m-2 intervals for morphological changes associated with floral initiation. Two phenotypes were identified, cultivars with an association between floral initiation and cumulative irradiance and those with association between floral initiation and chronological time. Genotypic variation was observed among the irradiance-associated phenotypes.

Effect of photoperiod and daily light integral on flowering of five Hibiscus sp.

The effect of daily light integral (DLI) (400–700 nm) and photoperiod on Hibiscus sp. growth and flowering was studied. Hibiscus coccineus (Medic.) Walt., Hibiscus cisplatinus St-Hil., Hibiscus moscheutos L. ‘Disco Belle Pink’, Hibiscus radiatus Cav., and Hibiscus trionum L. plants were grown under a 9 h (0730–1630 h) or 16 h (0600–2200 h) photoperiod in a greenhouse under ambient daylight plus supplemental high-pressure sodium lighting at 20±1 °C. Within each photoperiod plants were grown under four levels of supplemental irradiance to achieve four DLIs. Under the 9 h photoperiod, plants received an additional 0, 2, 4, or 8 mol m −2 per day. Under the 16 h photoperiod, plants received an additional 2, 4, 8, or 16 mol m −2 per day. Increasing DLI from 8.3 to 25.5 mol m −2 per day (ambient plus supplemental) decreased H. cisplatinus leaf number below the first flower from 26 to 18 leaves, regardless of photoperiod. DLI interacted with photoperiod to affect flowering of H. moscheutos and H. trionum. H. moscheutos leaf number below the first flower was 15±2 leaves under a 16 h photoperiod, regardless of DLI. Increasing DLI from 12.2 to 20.2 mol m −2 per day reduced H. moscheutos ‘Disco Belle Pink’ leaf number below the first flower from 24 to 18 leaves, under a 9 h photoperiod only. Increasing DLI did not affect H. trionum leaf number below the first flower bud initiated, but reduced leaf number below the first flower to open on plants grown under a 9 h photoperiod. H. radiatus flowered only under a 9 h photoperiod and leaf number below the first flower was not affected by DLI. Increasing DLI from 6.7 to 8.9 mol m −2 per day increased H. radiatus total flower bud number at first flower opening from 7±1 to 10±1 buds, but did not affect flower bud number of the other species. H. coccineus did not flower during the experiment.

541 Floral Initiation of Regal Pelargonium Grown at Varying Daily Light Integrals

Nine cultivars of Pelargonium × domesticum representing three germplasm sources were evaluated for the effect of daily light integral on floral initiation. Plants were grown at four daily light integrals: 5, 10, 15, or 20 mols/day for a 16-h photoperiod in environmental growth chambers at constant 15.5 °C. Meristems were examined at 50-mol intervals (0 to 350 mols) for morphological changes associated with floral initiation. Two phenotypes were identified, cultivars with an association between floral initiation and irradiance and those with association between floral initiation and chronological time. Genotypic variation was observed among the cultivars of each phenotype.

502 Intermittent CO2 Enrichment for Hydroponic Lettuce Production

CO2 enrichment increases efficiency of light utilization and rate of growth, thereby reducing the need for supplemental lighting and potentially lowering cost of production. However, during warmer periods of the year, CO2 enrichment is only possible intermittently due to the need to vent for temperature control. Previous research investigated the separate and combined effects of daily light integral and continuous CO2 enrichment on biomass accumulation in lettuce. The current research was designed to look at the efficiency with which lettuce is able to utilize intermittent CO2 enrichment, test the accuracy with which growth can be predicted and controlled, and examine effects of varying CO2 enrichment and supplemental lighting on carbon assimilation and plant transpiration on a minute by minute basis. Experiments included application of various schedules of intermittent CO2 enrichment and gas exchange analysis to elucidate underlying physiological processes. Same-day and day-to-day adjustments in daily light integrals were made in response to occasional CO2 venting episodes, using an up-to-the-minute estimate of growth progress based on an integration of growth increments that were calculated from actual light levels and CO2 concentrations experienced by the plants. Results indicated lettuce integrates periods of intermittent CO2 enrichment well, achieving expected growth targets as measured by destructive sampling. The gas-exchange work quantified a pervasive impact of instantaneous light level and CO2 concentration on conductance and CO2 assimilation. Implications for when to apply supplemental lighting and CO2 enrichment to best advantage and methods for predicting and controlling growth under intermittent CO2 enrichment are discussed.