Photosynthetic Physiology of Blue, Green, and Red Light: Light Intensity Effects and Underlying Mechanisms

Red and blue light are traditionally believed to have a higher quantum yield of CO2 assimilation (QY, moles of CO2 assimilated per mole of photons) than green light, because green light is absorbed less efficiently. However, because of its lower absorptance, green light can penetrate deeper and excite chlorophyll deeper in leaves. We hypothesized that, at high photosynthetic photon flux density (PPFD), green light may achieve higher QY and net CO2 assimilation rate (An) than red or blue light, because of its more uniform absorption throughtout leaves. To test the interactive effects of PPFD and light spectrum on photosynthesis, we measured leaf An of “Green Tower” lettuce (Lactuca sativa) under red, blue, and green light, and combinations of those at PPFDs from 30 to 1,300 μmol⋅m–2⋅s–1. The electron transport rates (J) and the maximum Rubisco carboxylation rate (Vc,max) at low (200 μmol⋅m–2⋅s–1) and high PPFD (1,000 μmol⋅m–2⋅s–1) were estimated from photosynthetic CO2 response curves. Both QYm,inc (maximum QY on incident PPFD basis) and J at low PPFD were higher under red light than under blue and green light. Factoring in light absorption, QYm,abs (the maximum QY on absorbed PPFD basis) under green and red light were both higher than under blue light, indicating that the low QYm,inc under green light was due to lower absorptance, while absorbed blue photons were used inherently least efficiently. At high PPFD, the QYinc [gross CO2 assimilation (Ag)/incident PPFD] and J under red and green light were similar, and higher than under blue light, confirming our hypothesis. Vc,max may not limit photosynthesis at a PPFD of 200 μmol m–2 s–1 and was largely unaffected by light spectrum at 1,000 μmol⋅m–2⋅s–1. Ag and J under different spectra were positively correlated, suggesting that the interactive effect between light spectrum and PPFD on photosynthesis was due to effects on J. No interaction between the three colors of light was detected. In summary, at low PPFD, green light had the lowest photosynthetic efficiency because of its low absorptance. Contrary, at high PPFD, QYinc under green light was among the highest, likely resulting from more uniform distribution of green light in leaves.

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Manipulation of Intraday Durations of Blue- and Red-Light Irradiation to Improve Cos Lettuce Growth

Frontiers in Plant Science ◽

10.3389/fpls.2021.778205 ◽

2021 ◽

Vol 12 ◽

Author(s):

Tomohiro Jishi ◽

Ryo Matsuda ◽

Kazuhiro Fujiwara

Keyword(s):

Blue Light ◽

Red Light ◽

Dry Weight ◽

Photosynthetic Photon Flux Density ◽

Light Irradiation ◽

Photon Flux ◽

Photon Flux Density ◽

Leaf Elongation ◽

Shoot Dry Weight ◽

Lettuce Growth

The morphology of plants growing under combined blue- and red-light irradiation is affected by the presence or absence of time slots of blue- and red-light mono-irradiation. The purposes of this study were to investigate the morphology and growth of cos lettuce grown under light irradiation combining several durations of blue and red light simultaneously and independent mono-irradiations of blue and red light during the day, and to clarify the effects of the durations of blue-light mono-irradiation and blue-light irradiation. Young cos lettuce seedlings were grown under 24-h blue-light irradiation with a photosynthetic photon flux density (PPFD) of 110μmol m−2 s−1 (B+0R) or under 24-h blue-light irradiation with a PPFD of 100μmol m−2 s−1 supplemented with 8 (B+8R), 16 (B+16R), and 24-h (B+24R) red-light irradiation with PPFDs of 30, 15, and 10μmol m−2 s−1, respectively (Experiment 1). The daily light integral was 9.50mol m−2 in all treatments. In Experiment 1, leaf elongation was promoted as the duration of red-light irradiation decreased and the duration of blue-light mono-irradiation increased. The maximum shoot dry weight was observed under the B+8R treatment. Growth was likely promoted by the expansion of the light-receptive area caused by moderate leaf elongation without tilting. In Experiment 2, young cos lettuce seedlings were grown as for Experiment 1, but blue- and red-light irradiation intensities were reversed (R+0B, R+8B, R+16B, and R+24B). Leaf elongation was promoted by the absence of blue-light irradiation (R+0B). The leaf surface was increasingly flattened, and the shoot dry weight was enhanced, as the duration of blue-light irradiation increased. Thus, cos lettuce leaf morphology may be manipulated by adjusting each duration of blue-light mono-irradiation, red-light mono-irradiation, and blue- and red-light simultaneous irradiation, which can, in turn, promote cos lettuce growth.

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Blue Light Monochromatic Irradiation for 12 Hours in Lighting Pattern with Combinations of Blue and Red Light Elongates Young Cos Lettuce Leaves and Promotes Growth under High Daily Light Integral

HortScience ◽

10.21273/hortsci15959-21 ◽

2021 ◽

pp. 1-6

Author(s):

Tomohiro Jishi ◽

Ryo Matsuda ◽

Kazuhiro Fujiwara

Keyword(s):

Flux Density ◽

Blue Light ◽

Light Emitting Diode ◽

Red Light ◽

Dry Weight ◽

Photosynthetic Photon Flux Density ◽

Photon Flux ◽

Photon Flux Density ◽

Photosynthetic Photon Flux ◽

Leaf Elongation

Cos lettuce was grown under different spectral photon flux density distribution (SPFD) change patterns with blue- and/or red light-emitting diode (LED) irradiation with a 24-hour cycle. Twelve treatments were designed with a combination of four relative SPFD (RSPFD) change patterns and three photosynthetic photon flux density (PPFD) levels. The RSPFD change patterns were as follows: BR/BR, simultaneous blue- and red-light irradiation (BR) for 24 h; R/BR, red-light monochromatic irradiation (R) for 12 h followed by 12 hours of BR; B/BR, blue-light monochromatic irradiation (B) for 12 hours followed by 12 hours of BR; and B/R, 12 hours of B followed by 12 hours of R. Each RSPFD change pattern was conducted at three daily average photosynthetic photon flux densities (PPFDave) of 50, 100, and 200 µmol·m−2·s−1. The RSPFD change patterns that included B (B/BR and B/R) resulted in elongated leaves. A low ratio of active phytochrome to total phytochrome under B was considered the reason for leaf elongation. Shoot dry weight was significantly greater under the RSPFD change patterns that included B when the PPFDave was 200 µmol·m−2·s−1. The leaf elongation caused by B would have increased the amount of light received and thereby promoted growth. However, excessive leaf elongation caused the plants to fall, and growth was not promoted under the RSPFD change patterns that included B when the PPFDave was 50 µmol·m−2·s−1. Thus, 12-hour B promoted growth under conditions in which leaf elongation leads to increases in the amount of light received.

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Effects of Blue and Red Light On Growth And Nitrate Metabolism In Pakchoi

Open Chemistry ◽

10.1515/chem-2019-0038 ◽

2019 ◽

Vol 17 (1) ◽

pp. 456-464

Author(s):

Xiao-Xue Fan ◽

Feng Xue ◽

Bo Song ◽

Long-Zheng Chen ◽

Gang Xu ◽

...

Keyword(s):

Blue Light ◽

White Light ◽

Red Light ◽

Glutamate Synthase ◽

Photosynthetic Photon Flux Density ◽

Continuous Illumination ◽

Photon Flux ◽

Photon Flux Density ◽

Key Enzymes ◽

Chlorophyll Contents

AbstractThis study investigated the effects of blue and red light on metabolites of nitrate, key enzymes, and the gene expression of key enzymes in pakchoi plants (Brassica campestris L. var. Suzhouqing). Plants were grown under three light quality treatments, namely, white light (W), red light (R) and blue light (B), at the same photosynthetic photon flux density (PPFD) of approximately 150 μmol m-2 s-1 for 48 hours of continuous illumination, and W was set as the control. The dynamics of net photosynthetic rate in pakchoi subjected to different light treatments were the same as the total chlorophyll contents: blue light > white light > red light. The nitrate reductase (NR) activity, nitrite reductase (NiR) activity, glutamine synthetase (GS) activity and glutamate synthase (GOGAT) activity were highest under blue light. Further, the expression levels of NR, NiR and GS genes were significantly higher under blue light. Under continuous illumination, the auxin content (IAA) in pakchoi leaves was highest under blue light, whereas the abscisic acid (ABA) content was highest under red light. In contrast, there was no significant effect for gibberellin (GA) under any type of light treatment.

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Supplemental Far-Red Light Stimulates Lettuce Growth: Disentangling Morphological and Physiological Effects

Plants ◽

10.3390/plants10010166 ◽

2021 ◽

Vol 10 (1) ◽

pp. 166

Author(s):

Reeve Legendre ◽

Marc W. van Iersel

Keyword(s):

Plant Biomass ◽

Incident Light ◽

Red Light ◽

Leaf Length ◽

Interactive Effects ◽

Photon Flux ◽

Photon Flux Density ◽

Dry Matter Accumulation ◽

Light Spectrum ◽

Canopy Size

Light-emitting diodes allow for the application of specific wavelengths of light to induce various morphological and physiological responses. In lettuce (Lactuca sativa), far-red light (700–800 nm) is integral to initiating shade responses which can increase plant growth. In the first of two studies, plants were grown with a similar photosynthetic photon flux density (PPFD) but different intensities of far-red light. The second study used perpendicular gradients of far-red light and PPFD, allowing for examination of interactive effects. The far-red gradient study revealed that increasing supplemental far-red light increased leaf length and width, which was associated with increased projected canopy size (PCS). The higher PCS was associated with increased cumulative incident light received by plants, which increased dry matter accumulation. In the perpendicular gradient study, far-red light was 57% and 183% more effective at increasing the amount of light received by the plant, as well as 92.5% and 162% more effective at increasing plant biomass at the early and late harvests, respectively, as compared to PPFD. Light use efficiency (LUE, biomass/mol incident light) was generally negatively correlated with specific leaf area (SLA). Far-red light provided by LEDs increases the canopy size to capture more light to drive photosynthesis and shows promise for inclusion in the growth light spectrum for lettuce under sole-source lighting.

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Spectral Transmittance of Selected Greenhouse Construction and Nursery Shading Material

Journal of Environmental Horticulture ◽

10.24266/0738-2898-8.3.118 ◽

1990 ◽

Vol 8 (3) ◽

pp. 118-121 ◽

Cited By ~ 2

Author(s):

M.J. McMahon ◽

J.W. Kelly ◽

D.R. Decoteau

Keyword(s):

Blue Light ◽

Red Light ◽

Construction Materials ◽

Photosynthetic Photon Flux Density ◽

Photon Flux ◽

Photon Flux Density ◽

Spectral Transmittance ◽

Radiation Transmission ◽

Solar Noon

Abstract Spectral transmittance properties of several greenhouse construction and shading materials were determined by measuring the quantity and quality of solar radiation transmission on non-clouded (sunny) days at solar noon. Spectral transmittance parameters included photosynthetic radiation (400–700 nm) and photomorphogenic radiation (660 nm (red light), 730 nm (far-red light), and 400–500 nm (blue light). Light available for photosynthesis was measured as photosynthetic photon flux density (PPFD) and photosynthetic radiation (PI). Photomorphogenic radiation was measured as far-red/red (FR/R) and blue light. Greenhouse construction materials included glass, chambered acrylic, chambered polycarbonate, and inflated plastic film. Various shade materials of different colors were evaluated. Photosynthetically active radiation transmission of construction materials ranged from approximately 95% transmission of direct sunlight with Exolite to less than 50% with tinted Lexan. Far-red/red values of shade materials ranged from 0.94 for Enduro Green to 5.58 for Cravo LS-7.

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Application of an Automatic Control System of Photosynthetic Photon Flux Density for LED-Low Light Irradiation Storage of Green Plants

HortTechnology ◽

10.21273/horttech.15.4.0781 ◽

2005 ◽

Vol 15 (4) ◽

pp. 781-786 ◽

Cited By ~ 5

Author(s):

Kazuhiro Fujiwara ◽

Toshinari Sawada ◽

Yoshikatsu Kimura ◽

Kenji Kurata

Keyword(s):

Flux Density ◽

Blue Light ◽

Red Light ◽

Dry Weight ◽

Photosynthetic Photon Flux Density ◽

Light Irradiation ◽

Photon Flux ◽

Photon Flux Density ◽

Photosynthetic Photon Flux ◽

Low Light

A light-emitting diode (LED)-low light irradiation (LLI) storage system was developed for suppressing the change in dry weight and maintaining the quality of green plants during long-term storage. In this system, the carbon dioxide (CO2) exchange rate was maintained at zero by automatically adjusting the photosynthetic photon flux density (PPFD) with a proportional-integralderivative (PID) controller. The voltage supplied to the LEDs was controlled by the difference between the inflow (400 μmol·mol-1) and outflow CO2 concentrations in the storage case. Grafted tomato (Lycopersicon esculentum; scion = `House Momotaro'; rootstock = `Anchor T') plug seedlings were stored at 10 °C for 35 days under four different LLI conditions as a system operating test: fixed red light irradiation at 2 μmol·m-2·s-1, PID-controlled red light irradiation with no blue light, and PID-controlled red light irradiation with blue light at 0.2 or 1.0 μmol·m-2·s-1. The results showed that the automatic PPFD control during LED-LLI helped suppress changes in dry weight during storage as expected. Furthermore, it was found that addition of a low percentage of blue light improved the morphological appearance of the seedlings and reduced the PPFD required to suppress the change in dry weight.

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Green light reduces elongation when partially replacing sole blue light independently from cryptochrome 1a

10.21203/rs.3.rs-53294/v1 ◽

2020 ◽

Author(s):

Xue Zhang ◽

Mehdi bisbis ◽

Ep Heuvelink ◽

Weijie Jiang ◽

Leo F. M Marcelis

Keyword(s):

Leaf Area ◽

Blue Light ◽

Stem Elongation ◽

Green Light ◽

Light Response ◽

Biomass Accumulation ◽

Photosynthetic Photon Flux Density ◽

Stem Length ◽

Photon Flux ◽

Photon Flux Density

Abstract Although green light is often neglected it can have several effects on plant growth and development. Green light is probably sensed by cryptochromes (crys), one of the blue light photoreceptor families. The aim of this study is to investigate the possible interaction between green and blue light and the involvement of crys in the green light response of plant photomorphogenesis. We hypothesize that green light effects on morphology only occur when crys are activated by the presence of blue light. Wild-type Moneymaker (MM), cry1a mutant (cry1a) and two CRY2 overexpressing transgenic lines (CRY2-OX3 and CRY2-OX8) of tomato (Solanum lycopersicum) were grown in a climate chamber without or with green light (30 µmol m− 2 s− 1) on backgrounds of sole red, sole blue and red/blue mixture, with all treatments having the same photosynthetic photon flux density of 150 µmol m− 2 s− 1. Green light showed no significant effect on biomass accumulation, nor on leaf photosynthesis and leaf characteristics such as leaf area, specific leaf area, and chlorophyll content. However, in all genotypes, green light significantly decreased stem length on a sole blue background, whereas green light did not affect stem length on sole red and red/blue mixture background. MM, cry1a and CRY2-OX3/8 plants all exhibited similar responses of stem elongation to green light, indicating that cry1a, and probably cry2, is not involved in this green light effect. We conclude that partially replacing blue light by green light reduces elongation and that this is independent of cry1a.

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Influence of Light Quality and Intensity on Biomass and Biochemical Contents of Hydroponically Grown Lettuce

HortScience ◽

10.21273/hortsci12796-17 ◽

2018 ◽

Vol 53 (8) ◽

pp. 1157-1163 ◽

Cited By ~ 2

Author(s):

Kui Lin ◽

Zhi Huang ◽

Yong Xu

Keyword(s):

Blue Light ◽

Sugar Content ◽

Soluble Sugar ◽

Red Light ◽

Green Light ◽

Physiological Parameters ◽

Photon Flux ◽

Photon Flux Density ◽

Significant Difference ◽

Hydroponically Grown

The effects of different light intensities and qualities on the biomass, physiological parameters, and biochemical contents of hydroponically grown lettuce (Lactuca sativa L.) were evaluated, with the aim of obtaining better quality and higher yield, as well as saving energy in lettuce cultivation. Three different light qualities, provided by red (R), green (G), and blue (B) light-emitting diodes (LEDs), were used to produce six different combinations of illumination: A1: R:G:B = 7:0:3 [photosynthetic photon flux density (PPFD) = 150 μmol·m−2·s−1]; A2: R:G:B = 6:2:2 (150 μmol·m−2·s−1); A3: R:G:B = 7:0:3 (120 μmol·m−2·s−1); B1: R:G:B = 3:0:7 (150 μmol·m−2·s−1); B2: R:G:B = 2:2:6 (150 μmol·m−2·s−1); and B3: R:G:B = 3:0:7 (120 μmol·m−2·s−1), and the fluorescent lamp (FL) at 150 μmol·m−2·s−1 was used as the control (CK). In most cases, treatment A2 resulted in higher biomass attributes, whereas higher physiological parameters were observed in treatment B2. However, a greater shoot dry weight (SDW) was observed in treatment A1. No significant difference was detected in chlorophyll [Chl (a + b)] and carotenoid (CAR) contents among the different treatments. Soluble sugar content was found the highest in treatment A1, although it was not significant compared with that observed in treatment A2. Soluble protein content was higher in treatments with a higher component of blue light. Vitamin C content was found the highest in treatment B3 and the lowest in treatment A1, whereas malondialdehyde (MDA) content was the highest in CK and the lowest in treatments B1 and B2. These results indicated that appropriate ratio of red to blue light can effectively promote the accumulation of biochemical compounds in lettuce and that replacement of a certain portion of red light, blue light, or both with green light was more effective in promoting plant growth and quality.

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Blue versus Red Light Can Promote Elongation Growth Independent of Photoperiod: A Study in Four Brassica Microgreens Species

HortScience ◽

10.21273/hortsci14286-19 ◽

2019 ◽

Vol 54 (11) ◽

pp. 1955-1961 ◽

Cited By ~ 2

Author(s):

Yun Kong ◽

Devdutt Kamath ◽

Youbin Zheng

Keyword(s):

Blue Light ◽

Light Emitting Diode ◽

Red Light ◽

Photosynthetic Photon Flux Density ◽

Elongation Growth ◽

Photon Flux ◽

Photon Flux Density ◽

Extension Rate ◽

Hypocotyl Length ◽

Led Lighting

An elongated stem has beneficial effects on microgreen production. Previous studies indicate that under 24-hour light-emitting diode (LED) lighting, monochromatic blue light, compared with red light, can promote plant elongation for some species. The objective of this study was to investigate whether shortened photoperiod can change blue vs. red light effects on elongation growth. The growth and morphology traits of arugula (Brassica eruca, ‘Rocket’), cabbage (Brassica oleracea, unknown variety name), mustard (Brassica juncea, ‘Ruby Streaks’), and kale (Brassica napus, ‘Red Russian’) seedlings were compared during the stage from seeding to cotyledon unfolding under two light quality × two photoperiod treatments: 1) R, monochromatic red light (665 nm) and 2) B, monochromatic blue light (440 nm) using continuous (24-hour light/0-hour dark) or periodic (16-hour light/8-hour dark) LED lighting. A photosynthetic photon flux density of ≈100 μmol·m−2·s−1 and an air temperature of ≈22 °C was used for the preceding treatments. After 7 to 8 days of lighting treatment, regardless of photoperiod, B promoted elongation growth compared with R, as demonstrated by a greater stem extension rate, hypocotyl length, or petiole length in the tested microgreen species, except for mustard. The promotion effects on elongation were greater under 24- vs. 16-hour lighting in many cases. Among the tested species, mustard showed the lowest sensitivity in elongation response to B vs. R, which was independent of photoperiod. This suggests that the blue-light-promoted elongation is not specifically from 24-hour lighting, despite the varying promotion degree under different photoperiods or for different species. The elongation growth promoted by blue LED light under a photoperiod of either 24 hours or 16 hours can potentially benefit indoor production of microgreens.

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EFFECTS OF SPECTRAL FILTERS ON GROWTH OF ROSA × HYBRIDA AND EXACUM AFFINE.

HortScience ◽

10.21273/hortsci.25.8.849a ◽

1990 ◽

Vol 25 (8) ◽

pp. 849a-849

Author(s):

Margaret J McMahon ◽

John W. Kelly

Keyword(s):

Light Quality ◽

Red Light ◽

Photosynthetic Photon Flux Density ◽

Photon Flux ◽

Photon Flux Density ◽

Textile Dye ◽

Light Spectrum ◽

Spectral Filters ◽

Leaf Chlorophyll ◽

Exacum Affine

The growth of Rosa × hybrida and Exacum affine under different spectral filters was evaluated. Three filters that altered light quality were developed. One, a red textile dye, filtered out much of the blue/green portion of the light spectrum but did not change far-red to red (FR/R) light ratio. Another, a blue textile dye, raised FR/R by filtering out a portion of red light. The third, a salt (copper sulfate) lowered FR/R by filtering out a greater portion of far-red than red light. Two controls were used that did not alter light quality. The filters were installed in specally built growth chambers. Photosynthetic Photon Flux Density (PPFD) was adjusted to equal values in each chamber. Plants of both species were significantly shorter and had higher leaf chlorophyll, when grown under the low FR/R filter.

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