Purple light can be produced by a single wavelength or the sum of two wavelengths
the verdict
CONTESTED
contested - the weight sits with the supporting side
refutedsupported
the weight of evidence
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The provided sources discuss color space models and light quality in biology but do not substantiate the specific claim that purple light is produced by a single wavelength or the sum of two wavelengths.
Light is one of the most crucial parameters for enclosed cannabis (<i>Cannabis sativa</i>) production, as it highly influences growth, secondary metabolite production, and operational costs. The objective of this study was to investigate and evaluate the impact of six light spectra on <i>C. sativa</i> ('Babbas Erkle Cookies' accession) growth traits and secondary metabolite (cannabinoid and terpene) profiles. The light spectra evaluated included blue (430 nm), red (630 nm), rose (430 + 630 nm, ratio 1:10), purple (430 + 630 nm, ratio 2:1), and amber (595 nm) LED treatments, in addition to a high-pressure sodium (HPS, amber-rich light) treatment as a control. All the LED light treatments had lower fresh mean inflorescence mass than the control (HPS, 133.59 g plant<sup>-1</sup>), and monochromatic blue light yielded the least fresh inflorescence mass (76.39 g plant<sup>-1</sup>). Measurement of Δ9-tetrahydrocannabinol (THC) concentration (%) and total yield (g plant<sup>-1</sup>) showed how inflorescence mass and THC concentration need to be analyzed conjointly. Blue treatment resulted in the highest THC concentration (10.17% m/m), yet the lowest THC concentration per plant (1.44 g plant<sup>-1</sup>). The highest THC concentration per plant was achieved with HPS (2.54 g plant<sup>-1</sup>). As with THC, blue light increased cannabigerol (CBG) and terpene concentration. Conversely, blue light had a lesser impact on cannabidiol (CBD) biosynthesis in this <i>C. sativa</i> chemotype. As the combined effects of the light spectrum on both growth traits and secondary metabolites have important ramifications for the industry, the inappropriate spectral design could cause a reduction in cannabinoid production (20-40%). These findings show promise in helping producers choose spectral designs that meet specific <i>C. sativa</i> production goals.
These findings show promise in helping producers choose spectral designs that meet specific C. sativa production goals. Keywords: THC, CBD, LED, HPS, light wavelength, terpenes status released display-pdf yes is-olf no is-manuscript no is-preprint no is-journal-matter no is-scanned no is-retracted no Received 2022 Sep 22; Accepted 2022 Oct 19; Collection date 2022 Nov. 1. Introduction Cannabis ( Cannabis sativa ) has been exploited as a medicinal plant for over two millennia [ 1 ]. With the global movement on cannabis legalization, C. sativa production has become one of the most rapidly expanding markets [ 2 , 3 ]. C.
Amber was significantly less than purple ( p ≤ 0.001), blue ( p = 0.008), rose ( p = 0.042) and HPS ( p = 0.027). α-Pinene was the second most abundant produced terpene for inflorescence cultivated under all light treatments. Blue light produced the most α-pinene (5.73 ± 0.38 mg g −1 ), followed by purple, HPS, rose, red, and amber light. Limonene was the third overall most produced terpene and inflorescence cultivated under purple light produced the most limonene (3.05 ± 0.12 mg g −1 ), followed by HPS, blue, rose, red, and amber light. Amber has significantly less limonene than purple ( p ≤ 0.001), HPS ( p = 0.041) and blue ( p = 0.044).
Light Treatment Impacts Total THC and CBD Yield per Plant Light treatment had a significant impact on CBG and terpene yield per plant ( p < 0.0001 and p < 0.01, respectively; Figure 5 ). CBG yield was highest in purple (0.029 ± 0.003 g plant −1 ), HPS (0.027 ± 0.004 g plant −1 ), blue (0.024 ± 0.002 g plant −1 ), rose (0.021 ± 0.003 g plant −1 ), red (0.012 ± 0.003 g plant −1 ) and amber (0.009 ± 0.002 g plant −1 ). Total terpenes produced per plant were greatest in plants cultivated under HPS light (0.78 ± 0.08 g plant −1 ).
Purple (0.60 ± 0.06 g plant −1 ) and rose (0.60 g ± 0.05 plant −1 ) produced equivalent amounts of terpenes, followed by red (0.49 ± 0.07 g plant −1 ), blue (0.41± 0.05 g plant −1 ) and amber light treatments (0.34 ± 0.04 g plant −1 ). Figure 5 Effect of light treatment on CBG and total terpene yield. Treatments are high-pressure sodium (HPS), rose (430 + 630 nm, B:R ratio 1:10), red (630 nm), amber (595 nm), purple (430 + 630 nm, B:R ratio 2:1), and blue (430 nm). Values presented in mean ± SE ( n = 3). Different letters (a, b) above the bars represent a significant difference between treatments by Tukey HSD ( p < 0.05). 2.5.
At a glance, the difference between the two spectra is a 6-fold increase in light intensity in the 700–799 nm range for HPS, as well as an absence of any wavelength >800 nm in the Rose LED spectrum. Influence of the Far-Red spectrum (700–780 nm) on cannabinoid yield should be further investigated. Unlike THC, CBD concentration did not seem to respond as much to increasing fractions of blue light. Comparable CBD percentages were found in the inflorescence of plants cultivated among blue, purple, rose, and HPS light treatments, while lower CBD percentages were observed in amber and red treatment.
Again, the interaction between light quality and chemotypes should be studied further, especially for growers working with CBG-dominant (type IV) chemotypes [ 58 ]. Cannabinoid concentration in C. sativa should always be analyzed in conjunction with biomass accumulation. In this study, HPS treatment produced the most cannabinoids (THC and CBD) on a per-plant basis. The light treatments containing blue light (blue and purple) resulted in 22 to 43 % less total THC yield per plant.
Terpenes Terpenes are responsible for inflorescence odor and flavor profiles [ 59 ]. Light treatments with blue-dominant spectra led to higher total terpene production, monoterpenes, and sesquiterpenes. Purple light treatment resulted in the highest total terpene concentrations (mg g −1 ), followed by the blue light treatment. Higher concentrations of monoterpenes and sesquiterpenes were observed under these two light treatments, with a higher fraction of blue light, and this data agree with a previous study [ 17 ], in which higher concentrations of monoterpenes such as α-pinene and limonene
light (each point representing a pure hue of a single wavelength), with wavelengths listed in nanometers. The straight edge on the lower part of the gamut
In 1931, the International Commission on Illumination (CIE) published the CIE 1931 color spaces which define the relationship between the visible spectrum and human colour vision. The CIE color spaces are mathematical models that comprise a "standard observer", which is a static idealization of the color vision of a normal human. A useful application of the CIEXYZ colorspace is that a mixture of t
The diagram represents all of the chromaticities visible to the average person. These are shown in color and this region is called the gamut of human vision. The gamut of all visible chromaticities on the CIE plot is the tongue-shaped or horseshoe-shaped figure shown in color. The curved edge of the gamut is called the spectral locus and corresponds to monochromatic light (each point representing a pure hue of a single wavelength), with wavelengths listed in nanometers. The straight edge on the lower part of the gamut is called the line of purples. These colors, although they are on the border of the gamut, have no counterpart in monochromatic light. Less saturated colors appear in the interior of the figure with white at the center.
It is seen that all visible chromaticities correspond to non-negative values of x, y, and z (and therefore to non-negative values of X, Y, and Z).
If one chooses any two points of color on the chromaticity diagram, then all the colors that lie in a straight line between the two points can be formed by mixing these two colors. It follows that the gamut of colors must be convex in shape. All colors that can be formed by mixing three sources are found inside the triangle formed by the source points on the chromaticity diagram (and so on for multiple sources).
An equal, additive mixture of two colors will not generally lie on the midpoint of that line segment, unless the sum of the X, Y, and Z
The new color matching functions were to be everywhere greater than or equal to zero. In 1931, computations were done by hand or slide rule, and the specification of positive values was a useful computational simplification.
The
y
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color matching function would be exactly equal to the photopic luminous efficiency function V(λ) for the "CIE standard photopic observer". The luminance function describes the variation of perceived brightness with wavelength. The fact that the luminance function could be constructed by a linear combination of the RGB color matching functions was not guaranteed by any means but might be expected to be nearly true due to the near-linear nature of human sight. Again, the main reason for this requirement was computational simplification.
For the constant energy white point, it was required that x = y = z = 1/3.
By virtue of the definition of chromaticity and the requirement of positive values of x and y, it can be seen that the gamut of all colors will lie inside the triangle [1, 0], [0, 0], [0, 1]. It was required that the gamut fill this space practically completely.
It was found that the
z
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(
λ
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{\displaystyle {\overline {z}}(\lambda )}
color matching function could be set to zero above
The diagram represents all of the chromaticities visible to the average person. These are shown in color and this region is called the gamut of human vision. The gamut of all visible chromaticities on the CIE plot is the tongue-shaped or horseshoe-shaped figure shown in color. The curved edge of the gamut is called the spectral locus and corresponds to monochromatic light (each point representing a pure hue of a single wavelength), with wavelengths listed in nanometers. The straight edge on the lower part of the gamut is called the line of purples. These colors, although they are on the border of the gamut, have no counterpart in monochromatic light. Less saturated colors appear in the interior of the figure with white at the center.
It is seen that all visible chromaticities correspond to non-negative values of x, y, and z (and therefore to non-negative values of X, Y, and Z).
If one chooses any two points of color on the chromaticity diagram, then all the colors that lie in a straight line between the two points can be formed by mixing these two colors. It follows that the gamut of colors must be convex in shape. All colors that can be formed by mixing three sources are found inside the triangle formed by the source points on the chromaticity diagram (and so on for multiple sources).
An equal, additive mixture of two colors will not generally lie on the midpoint of that line segment, unless the sum of the X, Y, and Z values of one color is equal to the sum of the X, Y, and Z values of the other color (that is, both colors lie in the same plane of the type X + Y + Z = n).
A distance on the CIE xy chromaticity diagram does not correspond to the perceived difference between two colors. In the early 1940s, David MacAdam studied the nature of visual sensitivity to color differences, and summarized his results in the concept of a MacAdam ellipse. Based on the work of MacAdam, the CIE 1960, CIE 1964, and CIE 1976 color spaces were developed, with the goal of achieving perceptual uniformity (have an equal distance in the color space correspond to equal differences in color). Although they were a distinct improvement over the CIE 1931 system, they were not completely free of distortion.
It can be seen that, given three real sources, these sources cannot cover the gamut of human vision. Geometrically stated, there are no three points within the gamut that form a triangle that includes the entire gamut; or more simply, the gamut of human vision is not a triangle.
Light with a flat power spectrum in terms of wavelength (equal power in every 1 nm interval) corresponds to the point (x, y) = (1/3, 1/3) (illuminant E).
The pupillary light reflex (PLR) is a neurological reflex driven by rods, cones, and melanopsin-containing retinal ganglion cells. Our aim was to achieve a more precise picture of the effects of 5-min duration monochromatic light stimuli, alone or in combination, on the human PLR, to determine its spectral sensitivity and to assess the importance of photon flux. Using pupillometry, the PLR was assessed in 13 participants (6 women) aged 27.2 ± 5.41 years (mean ± SD) during 5-min light stimuli of purple (437 nm), blue (479 nm), red (627 nm), and combinations of red+purple or red+blue light. In addition, nine 5-min, photon-matched light stimuli, ranging in 10 nm increments peaking between 420 and 500 nm were tested in 15 participants (8 women) aged 25.7 ± 8.90 years. Maximum pupil constriction, time to achieve this, constriction velocity, area under the curve (AUC) at short (0-60 s), and longer duration (240-300 s) light exposures, and 6-s post-illumination pupillary response (6-s PIPR) were assessed. Photoreceptor activation was estimated by mathematical modeling. The velocity of constriction was significantly faster with blue monochromatic light than with red or purple light. Within the blue light spectrum (between 420 and 500 nm), the velocity of constriction was significantly faster with the 480 nm light stimulus, while the slowest pupil constriction was observed with 430 nm light. Maximum pupil constriction was achieved with 470 nm light, and the greatest AUC0-60 and AUC240
Maximum pupil constriction was achieved with 470 nm light, and the greatest AUC 0−60 and AUC 240−300 was observed with 490 and 460 nm light, respectively. The 6-s PIPR was maximum after 490 nm light stimulus. Both the transient (AUC 0−60 ) and sustained (AUC 240−300 ) response was significantly correlated with melanopic activation. Higher photon fluxes for both purple and blue light produced greater amplitude sustained pupillary constriction. The findings confirm human PLR dependence on wavelength, monochromatic or bichromatic light and photon flux under 5-min duration light stimuli.
Since the most rapid and high amplitude PLR occurred within the 460–490 nm light range (alone or combined), our results suggest that color discrimination should be studied under total or partial substitution of this blue light range (460–490 nm) by shorter wavelengths (~440 nm). Thus for nocturnal lighting, replacement of blue light with purple light might be a plausible solution to preserve color discrimination while minimizing melanopic activation.
Tristability (with two silent and one signaling state) has also been suggested as a mechanism for ipRGC to integrate both time and wavelength ( 33 ). However, not all studies have been able to demonstrate this long wavelength potentiation of blue light responses ( 34 , 35 ), while some studies have proposed the existence of retinal pigment epithelium (RPE)-derived regeneration in melanopsin ( 36 , 37 ), which could be interpreted as a complementary mechanism [reviewed in ( 38 )].
The study of possible interactions between two monochromatic wavelengths when administered simultaneously, as well as assessment of PLR sensitivity over a high resolution short wavelength range will help to provide knowledge on the effect of polychromatic lights on the PLR. The aim of this study was thus to achieve a more precise picture of the effects of 5-min monochromatic light stimuli, alone or in combination [long (red) combined with short (blue and purple) wavelength lights], on the human PLR (including PIPR), to determine its spectral sensitivity and to confirm the importance of photon flux as a determinant of the human PLR.
Based on previous knowledge, we hypothesized that blue or purple light would produce different responses when combined with red light as a result of melanopsin bistability, probably increasing the
Similarly, in the sustained response (AUC 240−300 ) there were no significant differences between the different light conditions (although significant overall effect, Friedman's test, χ 2 = 10.8, df = 4, p = 0.029), although blue light alone or in combination tended to produce a more sustained higher amplitude response (blue, 1,908 ± 241 A.U.; blue + red, 2,076 ± 260) than purple (purple 1,350 ± 191 A.U.; purple + red 1,740 ± 222 A.U.) or red (1,456 ± 311 A.U.) light wavelengths.
Photon flux comparison The effect of light intensity on the PLR was compared for purple (~440 nm) and blue (~480 nm) light considering the highest (Study A, 1.2 × 10 13 photons/cm 2 /s or ~13 log quanta/cm 2 /s) and lowest (Study B, 8 × 10 11 and 9.2 × 10 11 photons/cm 2 /s, respectively or ~12 log quanta/cm 2 /s) photon fluxes. Figure 9 represents the average PLR recording for each wavelength (Figure 9A , purple light; Figure 9B , blue light) at ~13 log quanta/cm 2 /s and ~12 log quanta/cm 2 /s photon fluxes. As expected, higher photon fluxes produced a greater transient and sustained pupillary constriction for both wavelengths than lower photon fluxes.
14.3 ± 0.9%/s lower photon flux, p = 0.035). Purple light also tended to be faster, although statistical significance was not reached (15.7 ± 1.1 higher vs. 12.2 ± 1.4 %/s lower photon flux, p = 0.207). The velocity of pupil constriction was significantly affected by both wavelength (one-way repeated measures ANOVA, F = 5.007, df = 1, p = 0.038) and photon flux ( F = 5.466, df = 1, p = 0.031), interaction between these factors was not significant (one-way mixed design ANOVA).
The shorter (purple) wavelengths (420–440 nm) would activate S-cones so the lower amplitude pupil response found with these wavelengths may also be due to spectral opponency ( 49 , 50 , 54 ), these lights thus producing less constriction than the longer wavelengths with melanopsin activation. The 6-s PIPR parameter, calculated after 5-min light stimuli, also showed greater constriction (smaller diameters) with longer wavelengths, again the maximum pupil constriction being at 490 nm.
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