Information About Grow Light Spectrum, PAR, Photosynthesis, Leaf Surface Temperature

[CannaRed]

Red to Blue spectrum ratio affect on growth example:

So this is showing different results than isaacks experiment?

So it's probably strain specific, like everything else.

Plants want the red/blue spectrum of their parental origin countries?

Thanks for compiling this info. Now I need help deciphering. Lol

 

[Ibechillin]

Just an example on how spectrum can effect morphology, I just mentioned something a moment ago in another thread about genetics being the main factor haha.

 

[Ibechillin]

Found these charts demonstrating the change in the suns spectrum:

Morning daylight spectrum change:

Noon Daylight D65 is what plants are exposed to in full sun, comprised of direct sunlight and light being reflected/diffused from the surface and other objects, Noon Sunlight D55 is like a ray of light into a dark room, Sunset Sky self explanatory haha.

Light intensity (umol/m2/s = PPFD) and C02 level required for max photosynthesis:

 

[gmanwho]

The Spectrum change an Co2 light intensity graphs are great. think thats the first time ive seen any graphs of that aspect. I Always knew there was a change in sunlight throughout the day, season, lat/longitude, an altitude. but to see it on a graph is interesting.

any chance any more info on the light spectrum graphs. like where the reading was taken in accordance to latitude/longitude of the readings,altitude, time of year? im sure that all plays a part.



just talking out loud here, so the PAR is light for photosynthesis. you know of any other graphs for things like uv exposure. or other wavelengths that help the plant in other ways? wave lengths that trigger certain pheromones like the deep red light?


i remember reading some time ago that higher uva uvb would increase the trichome production or increase similar components within the trichome. after all the trichomes purpose was to shield an protect, diffuse the light from the sun. In all the effort to protect the seed from the suns harmful light rays an heat. Without the trichome the sun light/uv an heat would sterilize the seed. preventing any chance of viable seed to drop an start the next spring.

in your opinion, do you think this holds true?

just sparked a memory of a led mfg at a cannabis conference in boston, was looking at his par charts an i asked if there was any UV leds in the boards. he said no, we dont need uv. i thought that was funny. but maybe im wrong?

thanks for sharing!!
b-well

 

[Ibechillin]

In the first post of the thread under the spectrum pic of the sun there are charts of the absorption and action spectrum. The PAR range is only 400nm-700nm and both charts show activity below 400nm which is the UV wavelengths and the action spectrum shows activity above 700nm in the infrared wavelengths as well.

The spectrum of light produced by the sun is constant and the atmosphere filters it before reaching earth's surface causing the changes shown in the different charts.

This image gives an idea of how lattitude/angle of light effects the spectrum received:
(at noon light travels straight down shortest path/least interference)

At sunrise and sunset light travels through much more of the atmosphere and debris within it (moisture, dust, clouds etc) causing "scattering" which alters the light we receive. Rayleigh scattering is the scattering of light by particles much smaller than the wavelength of the radiation. The shorter wavelength blues are scattered more strongly than longer red wavelengths, this results in indirect blue light coming from all regions of the sky. Mie scattering is when the water vapor and water droplets direct more of the blue wavelengths of light back where they came from instead of to the earth's surface, causing us to receive less blue. I read a post by someone on stackexchange earlier that was explaining 30 degrees north or south from the equator the suns path doesnt change enough to alter the spectrum, then as you get further from the equator the spectrum begins to be impacted.

In my post before this one the morning spectrum change chart was recorded at the National Research Institute of Astronomy and Geophysics (NRIAG) in Helwan, Egypt. The next picture showing noon daylight/sunlight and sunset illuminants are industry accepted standards.

Here is an example of daylight spectrum change at different seasons recorded at the National Institute of Solar Energy in Gurugram Central India:

Winter season October to February
Summer Season mid March to June
Monsoon season July to mid September
Post Monsoon season mid September to mid November

Here are daylight spectrum recordings at different times of day (8am to 3pm) from Boulder, Colorado at 5334ft elevation.

This is a map of the USA showing average Daily Light Integral for each month:
(I found this DLI map in Ed Rosenthal's Marijuana Growers Handbook, he mentons the Western half of the USA receives ~50% more light than the Eastern half! I attached a screenshot with the caption from beneath the DLI map in his book explaining):

 

[Ibechillin]

Gavita says HPS emits ~55-58% of its spectrum in infrared light, MH and CMH would be near that as well. This is probably the reasoning behind recommending replacing 1000w HPS with ~600W of quality led. Another interesting thing Gavita mentions about growing under led with minimal IR is needing to increase nutrient strength by up to 25% compared to HPS since the plants dont transpire as much.

Here is the link to the Gavita editorial on LED that I found the information in:

https://gavita.com/retail/app/uploads/Garden-Culture-editorials-4.pdf

Emerson effect and more phytochrome information:

Robert Emerson proved that there are 2 different photosystems active in plants that absorb different parts of the light spectrum. Photosystem I absorbs and reacts with light above 680nm (the infrared photosytem), Photosystem II absorbs light below 680nm (UV and visible spectrum). He discovered this by testing how plants responded to different spectrums of monochromatic light (one wavelength/color only). He noticed between 660nm - 680nm red light wavelengths only the photosynthetic activity was highest and declined above and below those wavelengths. Then he experimented exposing the plant to the max photosynthetic active range (660nm-680nm red) and far red 700nm simultaneously and photosynthetic activity increased exponentially. Chlorophyl A absorption peak is 662nm and provides the most usable energy for growth and is also in the Photosytem II max activity range (660nm - 680nm).

Emerson Effect On Photosynthetic Ability Example:

Here Is Link To A Study Im Currently Reading:

https://www.researchgate.net/publication/273057363_Far-Red_Spectrum_of_Second_Emerson_Effect_A_Study_Using_Dual-Wavelength_Pulse_Amplitude_Modulation_Fluorometry

Relevant Excerpt:

FRIFS = Far Red Induced Fluorescence Shift

The involvement of PSI in the FRIFS phenomenon as a factor limiting the non-cyclic electron transport is clearly confirmed by the fact, that in our experiments FRIFS has a lower value when the fluorescence was excited by red modulated light instead blue light (FRIFS = 2.5% under 640 nm light and 11.8% under 470 nm light-both at 0.1 µmol photons m–2 s–1). It should be noticed here, that blue light at 470 nm preferentially excites PSII, whereas 620-640 nm light excites both photosystems nearly equally (Hogewoning et al., 2012).

Here are results of 470nm blue along with different far red wavelengths:
(It appears that the largest increase in Photosynthetic activity comes from mixing blue light ~470nm and infra red light at 720nm simultaneously).

More interesting information about phytochromes from Ed Rosenthal's Marijuana Growers Handbook I wanted to share:

Plants use blue light to regulate flowering as well as for photosynthesis. Blue light is not as efficient a source of energy for photosynthesis as red light indoors because blue light has a higher energy value than red light and it requires more
energy to produce than red light. However, the plant obtains the same amount of energy from both of them.

Blue light is another option for sexing. As mentioned earlier in this chapter, marijuana flowering is very sensitive to red light of specific spectrums. Any interruption of the dark period with light that contains the red, 660 nm spectrum returns the flowering hormone Pr back to its inactive state, Pfr. This prevents flowering.

Blue light at 400-450 nm also has an inhibitory effect on flowering, but its effect is weaker than red light. Plants grow some flowers when blue light is kept on during the dark period; however, they continue to grow vegetatively as well. If you use blue LED or fluorescent lights to provide the plants with nothing but pure blue light, they will get enough stimulation to produce some flowers for sexual identification but not go into full flowering mode. Once all the plants indicate, replace the blue light with a full spectrum light period to keep the plants growing vegetatively. When blue light is turned on during the dark period, plants photosynthesize, but the growth from the blue light is not significant. The stems grow a little more stocky. See the Phytochrome Response chart, which shows phytochrome Pr-Pfr sensitivity across the light spectrum. The red-far-red portion shows high activity. The blue spectrum shows just a little bump. This indicates a slight activity. The result is sporadic flowering on all the plants. You can create a pure blue light with LEDs and blue CFLs. Use about 200 watts of mixed blue light per 1,000 watts of regular light. I have done only initial experimentation with this so test this in a limited way first.

I posted this on 2-6-2019 in DC's optimal spectrum thread:

Link to DC's optimal spectrum thread:

https://www.icmag.com/ic/showthread.php?t=359554

The research ive done on far red lighting suggests you only need the high far red ratio to simulate the sunset conditions outdoor during the last ~30 minutes of the lights on period for the stretch response.

In the link I attached at the bottom it explains daylight is around a red:far red ratio of 1.15 (15% more red light) to 1.37 (37% more red light). At sunset the red:far red ratio is closer to 0.7 (30% more far red light).

The link explains that by covering greenhouses with blackout tarps before the high far red sunset lighting reaches the plants final height could be reduced up to 25%.

Link to study on red:far red ratio and plant growth:

https://journals.ashs.org/hortsci/view/journals/hortsci/42/7/article-p1609.xml

i remember reading some time ago that higher uva uvb would increase the trichome production or increase similar components within the trichome. after all the trichomes purpose was to shield an protect, diffuse the light from the sun. In all the effort to protect the seed from the suns harmful light rays an heat. Without the trichome the sun light/uv an heat would sterilize the seed. preventing any chance of viable seed to drop an start the next spring.

in your opinion, do you think this holds true?

just sparked a memory of a led mfg at a cannabis conference in boston, was looking at his par charts an i asked if there was any UV leds in the boards. he said no, we dont need uv. i thought that was funny. but maybe im wrong?

thanks for sharing!!
b-well

In the thread a few pages back I linked a study that tested different light types and spectrums on cannabis to compare the end result differences and it was determined Light intensity did not affect total Cannabinoid content. When a plant gets pollinated it stops producing trichomes and focuses entirely on producing seeds. In this regard it would seem the trichome's only purpose is to collect pollen from males, since the female plants produce more and more trichomes as they get closer to senescence. I discovered trichomes on the adaxial (top) side of leaves have high concentrations of silicon compared to the ones on the abaxial (bottom) side when I was researching into trichome anatomy and development in different plants. This leads me to believe they are used in effort to reduce potential damage from UV Light specifically.

Researching into UV light and cannabis interaction my determination is that UVA and UVB can increase total THC content by ~10% of its original amount (20% THC plant grown without UV could increase to 22% THC grown with UV supplemented). So yes, UV is not necessary for growth but *could* be beneficial to cannibinoid production. (I have a bunch of links about UV and cannabis on the first page also).

 

[Douglas.Curtis]

When a plant gets pollinated it stops producing trichomes and focuses entirely on producing seeds. In this regard it would seem the trichome's only purpose is to collect pollen from males, since the female plants produce more and more trichomes as they get closer to senescence.

I never understood how producing more of a sticky item which forever traps pollen and makes it useless, is somehow supposed to help with pollination??

Makes me question a lot of things...

 

[Ibechillin]

Yeah, the "why did cannabis evolve to produce cannabinoids?" question is an interesting one.

Getting more complicated even is:

Why does cannabis form the medicinal compounds in the trichomes dissimilar from other trichome developing plants like tomatoes?
Why do brains have an endocannabinoid system?
Why did cannabis evolve to produce the same/similar compounds our body produces naturally for necessary physiological processes?

 

[Ibechillin]

I was pretty sure cannabis doesn't produce cannabinoids until after flower initiates but wanted to search and verify before mentioning it (still reading into deeper). Cannabis does produce trichomes during veg growth, just not the capitate stalked trichomes with cannabinoids in them, they are similar to the ones found on a tomato plant. Terpenes are produced during veg growth and are found in many other plant species as well, they are believed to be used as defense/survival mechanisms so it makes sense why they produce them. Cannabinoids are terpenophenolic compounds meaning they are part terpene also.

Since cannabinoids only form from flower start until pollination happens its really a mystery why they develop them at all???

 

[CannaRed]

I was pretty sure cannabis doesn't produce cannabinoids until after flower initiates but wanted to search and verify before mentioning it (still reading into deeper). Cannabis does produce trichomes during veg growth, just not the capitate stalked trichomes with cannabinoids in them, they are similar to the ones found on a tomato plant. Terpenes are produced during veg growth and are found in many other plant species as well, they are believed to be used as defense/survival mechanisms so it makes sense why they produce them. Cannabinoids are terpenophenolic compounds meaning they are part terpene also.

Since cannabinoids only form from flower start until pollination happens its really a mystery why they develop them at all???

I've heard of testing companies that can give you a CBD/THC ratio from a veg sample. They said the percentages (of final dry weight) will change, but the ratio will be the same.
Thoughts?
Tried to talk to Steep Hill representative at the National Cannabis Festival about this, but she was lost. Not sure that she actually worked for Steep Hill, because couldn't answer basic questions. Just kept repeating a sales pitch she had memorized.

 

[St. Phatty]

I was pretty sure cannabis doesn't produce cannabinoids until after flower initiates but wanted to search and verify before mentioning it (still reading into deeper). Cannabis does produce trichomes during veg growth, just not the capitate stalked trichomes with cannabinoids in them, they are similar to the ones found on a tomato plant. Terpenes are produced during veg growth and are found in many other plant species as well, they are believed to be used as defense/survival mechanisms so it makes sense why they produce them. Cannabinoids are terpenophenolic compounds meaning they are part terpene also.

Since cannabinoids only form from flower start until pollination happens its really a mystery why they develop them at all???

I used to do all edibles, and I made the edibles from growing tips of Sativa dominant plants - no flowers.

That was my routine for a few years.

There is something very Cannabis-like in the leaves, that does get you high.

 

[gmanwho]

Thank you for taking the time to post an reference.

 

[CannaRed]

I've seen small cuttings in veg with Trichomes. I think it was labeled GSC. Doesn't have it all the time but my mentor saw it at his grow on same cut.

I have no idea what the cannabinoid content was, and now I wish I had looked under my scope to see what kind of trichomes they were.
No idea why the plant only did it a few times and even stranger- it happen at different grows, but at same times. Inside under different lights and different environments.

 

[Ibechillin]

I've heard of testing companies that can give you a CBD/THC ratio from a veg sample. They said the percentages (of final dry weight) will change, but the ratio will be the same.
Thoughts?

I used to do all edibles, and I made the edibles from growing tips of Sativa dominant plants - no flowers.

That was my routine for a few years.

There is something very Cannabis-like in the leaves, that does get you high.

I found a paper from Steep Hill labs and a study just now that seem to have the answers we are looking for . They use the same procedures they test flowers with to test veg samples or they can do DNA testing for the chemotype.

Sampling Cannabis for Analytical Purposes by Steep Hill Labs

https://lcb.wa.gov/publications/Marijuana/BOTEC%20reports/1e-Sampling-Lots-Final.pdf

"In 2003, GW Pharmaceutical published a paper in Genetics which stated: “there is little doubt that environmental factors have a strong influence in modulating the amount of cannabinoids present in the different parts of the plants at different growth stages.” However, they report that cannabinoid profiles in general are under strong genetic control (the THC to CBD ratio, specifically) and that plants typically demonstrate high degrees of polymorphisms (or spontaneous genetic mutations) - up to 80% measured in fiber type plants which can account for variability (de Meijer et al. 2003). For plants that were double inbred clones (S2’s: female lines with “pure fixed” chemotype), major cannabinoids ranged from between 84-98% of total cannabinoid fractions."

Time course of cannabinoid accumulation and chemotype
development during the growth of Cannabis sativa L

https://www.votehemp.com/wp-content/uploads/2018/09/D.Pacifico2007Euphtyca.pdf

"The CBD/THC and CBG/CBD ratios were shown to be largely constant in the leaves, since 28 and until 103 days after sowing, CBD and THC maximum amounts in the leaves showed a peak in the leaves around 80 days from sowing"

"Cannabinoids are terpenophenolic substances, differing in the structure of their terpenic moiety and/or the length of the prenyl side chain attached to the phenolic portion. In vivo, they are present as acidic forms (THCA, CBDA, CBCA), that are decarboxilated in the corresponding neutral forms as consequence of heating or drying. In this paper,cannabinoids will be referred to by their neutral forms (e.g., THC, CBD). Cannabinoids are present in all the aerial parts of the Cannabis plant, correlated with the presence of glandular trichomes, stalked or sessile, especially present on bracts and leaves (Turner et al 1978). The pathway and the site of biosynthesis of cannabinoids has not been completely clarified but some authors supposed that cannabinoids are synthetized in specialized disc cells, present in the glandular trichomes, accumulated in the adjacent secretory cavity and finally exuded as resin (Mahlberg and Kim 2004) or, alternatively, that the cannabinoid synthases themselves are secreted (Sirikantaramas et al. 2005). It is commonly accepted that the first cannabinoid synthetized is cannabigerol (CBG), produced by condensation of a phenol-derived olivetolic acid and a terpene-based geranyl diphosphate catalysed by GOT (geranyldiphosphatelivetolate geranyltransferase; Fellermeier and Zenk 1998; Fellermeier et al. 2001). From CBG, THC, CBD and CBC are synthesized, each by a specific synthase (Sirikantaramas et al. 2004).

Several C. sativa variants with different phenotypes characterized by specific cannabinoid ratios and quantities, have been described (chemotypes; Small and Beckstead 1973). Chemotype I is the “drug” type, with a THC amount over 0.30% of inflorescence dry
weight, and a CBD content lower than 0.50% (i.e., with low CBD/THC ratio). Chemotype II, the intermediate type, has both CBD and THC, in a ratio around the unity (typically 0.5–2.0); chemotype III, the “fibre” type, has mainly CBD, and a level of THC lower than 0.30% (down to undetectability). Later, two other chemotypes were defined: chemotype IV has a prevalence of CBG (>0.30%), but also CBD (<0.50%; Fournier et al. 1987); and chemotype V, with amounts of all cannabinoids practically undetectable by standard gas-chromatographic analysis (Mandolino and Carboni 2004).

Recent genetic analyses demonstrated that the cannabinoid type (i.e., the chemotype) a Cannabis plant is endowed with, is determined by the allelic status at a single locus, B; as a consequence of this simple determinism, chemotype can be easily introgressed and segregates into any genetic background (de Meijer et al. 2003; Mandolino et al. 2003; Pacifico et al. 2006). A variety of studies demonstrated that the overall cannabinoid amount is dependent upon several factors. A cool summer can reduce the cannabinoids contents of the same accession (Latta and Eaton 1975; de Mejer 1992); dry and windy conditions can raise cannabinoids content, and the THC content of leaves was reported to decrease after consistent nitrogen fertilization (Bócsa et al. 1997). According to other authors, total cannabinoid content is also dependent on plant sex and developing phase of the plant (Fetterman et al. 1971; Fairbairn and Rowan 1975).

It is also known that in proximity of flowering, the cannabinoid content reaches its maximum in trichome-rich organs; on the contrary, no cannabinoids were reported in roots and seeds, and a few reports analyzing the cannabinoid production of cultured hemp cells were unable to detect any THC or CBD (reviewed in Mandolino and Ranalli 1999).

Plants of each strain were grown in a greenhouse under environmental conditions: the temperature varied during the growth of the plants between 24°C and 34°C (April-August), and the photoperiod was kept at 16:8 (light:dark) by artificial lighting when necessary. The duration of the growth period was dependent on the earliness of the different accessions, and showed wide individual variation. By the end of august, however, i.e., about 180 days after planting, all the plants had flowered.

Starting from 28 days after planting, when, under our conditions, the Cannabis plantlets were at 3rd leaf stage one young expanded leaf was periodically picked up from each plant of each accession, and individually analysed by GC. The last leaf sampling was made at 103 days after planting. Because it was necessary to avoid the effects of the leaf age on cannabinoid analysis, the leaves sampled were always the most expanded ones placed at the sub-apical stem node of the plant. For GC analyses, all the samples (leaves, reproductive parts and calli) were dried at 65°C for 48 h, powdered, weighed, and 100 mg d.w. were individually analysed by gas-cromathography to quantify THC, CBD and CBG.

In Fig. 1, the time course of the average total cannabinoid content in the leaves of the three accessions (strains) examined is shown. The average amount increased similarly for all accessions until about 60 days after planting, as shown by the extensive overlapping of the three curves. After 60 days after planting, standard deviations greatly increased as cannabinoids are further accumulated,
indicating a high variability among the leaves sampled.

(Remember this chart is only showing cannabinoids from fan leaves in veg)

 

[Ibechillin]

Bump, finished explaining above. Here is info on cannabinoid testing procedures used:

https://www.perkinelmer.com/lab-solutions/resources/docs/APP_Cannabis-Analysis-Potency-Testing-Identifification-and-Quantification-011841B_01.pdf

Two analytical techniques have been successfully used for the potency testing of cannabis: Gas chromatography (GC) and High Performance Liquid Chromatography (HPLC). There are advantages and disadvantages to each technique. Refer to any specific guidelines offered by the state regulations for suggested analytical technique.

• Total THC is of primary interest in cannabis potency testing along with the THC/CBD ratio for therapeutic value.

• Total THC = THC + THCA

• Total CBD = CBD + CBDA (each must be corrected for weight of the carboxylic acid groups)

HPLC can identify the acid components of THCA and CBDA before conversion to their corresponding free forms of THC and CBD. This is often preferred for edible materials and extracted tinctures. This procedure can also be used for the original plant material potency testing and cannabinoid ratio calculations. GC does not detect THCA or CBDA directly. The carboxylic acids decarboxylate in the intense heat of smoking, baking or GC injector port. THCA decarboxylates to THC and CBDA decarboxylates to CBD.

GC converts the acid forms to the free cannabinoids by in-situ decarboxylation in the heat of the injector, but the conversion may be incomplete depending on temperature and injector considerations. Heating the sample before analysis can produce a more reliable conversion and may be worth the extra moments for more accurate reporting. GC generally mimics the conversion process during smoking of plant material. GC is generally considered faster and simpler than HPLC so it is often preferred. GC/FID is preferred for speed of analysis and simplicity in routine identification and quantification of cannabinoid concentrations. For positive identification of each cannabinoid, gas chromatography with a mass spectrometer would be preferred. A GCMS system with a second injector and a FID in a second channel makes for a versatile hardware configuration. The GCMS channel can use a small diameter capillary column for higher resolution and reduced flow rate. The MS will also be necessary for other cannabis testing such as terpenoids and pesticide analysis.

Using gas chromatography, cannabis potency is based on the concentration of decarboxylated THC and CBD.

Using HPLC, cannabis potency testing is based on sum of THC and THCA.

For THC/CBD analysis, leafy cannabis is extracted with organic solvent to dissolve oily resin on the surface of the plant material. Solvents that have been used successfully include methanol, isopropanol, ethyl acetate and others. The supernatant of the extract is injected into a gas chromatograph for separation and detected by either a flame ionization detector or by a mass spectrometer for positive identification.

 

[Lost in a SOG]

Don't ignore the green light

Don't ignore the green light

Don't ignore the green light: exploring diverse roles in plant processes.Review article

Smith HL, et al. J Exp Bot. 2017.

Show full citation

Abstract

The pleasant green appearance of plants, caused by their reflectance of wavelengths in the 500-600 nm range, might give the impression that green light is of minor importance in biology. This view persists to an extent. However, there is strong evidence that these wavelengths are not only absorbed but that they also drive and regulate physiological responses and anatomical traits in plants. This review details the existing evidence of essential roles for green wavelengths in plant biology. Absorption of green light is used to stimulate photosynthesis deep within the leaf and canopy profile, contributing to carbon gain and likely crop yield. In addition, green light also contributes to the array of signalling information available to leaves, resulting in developmental adaptation and immediate physiological responses. Within shaded canopies this enables optimization of resource-use efficiency and acclimation of photosynthesis to available irradiance. In this review, we suggest that plants may use these wavelengths not just to optimize stomatal aperture but also to fine-tune whole-canopy efficiency. We conclude that all roles for green light make a significant contribution to plant productivity and resource-use efficiency. We also outline the case for using green wavelengths in applied settings such as crop cultivation in LED-based agriculture and horticulture.

Introduction

Is the importance of green light hidden in plain sight? It is a misconception that plants do not make use of the green regions of the spectrum; a view which is perhaps understandable given the substantial amounts of this colour that are reflected, giving plants their pleasant and near-ubiquitous green appearance on Earth. However only around 10–50% of green light (between the wavelengths (λ) of 500 and 600 nm) is reflected by plant chloroplasts (Terashima*et al., 2009;*Nishio, 2000). The rest is absorbed by plant pigments or transmitted to shaded parts of the plant. There is strong evidence to suggest that green light plays a vital role in photosynthesis and physiological responses to the environment.

There is a growing pool of research showing that plants use green wavelengths to assimilate CO2, to promote higher biomass and yield, and as a crucial signal for long-term developmental and short-term dynamic acclimation to the environment. This review discusses the evidence for the ability of green light to penetrate deep into the mesophyll layers at the single-leaf level, and the lower layers of leaves on a canopy level, therefore driving photosynthesis where other wavelengths are in limited supply. We also detail how green light provides signals for acclimation to irradiance on a whole-plant to chloroplast scale, leading to improved leaf and crop productivity and yield. We hypothesize that green light profiles in canopies make it ideally suited to provide rich information for signalling and fine-tuning developmental and dynamic acclimation to shade, and may act as a secondary layer of control to the well-known red/far-red (FR)-light responses. We show evidence that wavelengths of 500–600 nm permit a finer control of water loss via changes in stomatal aperture in leaves within a canopy. However, we start by outlining the case for inclusion of green light in controlled growth environments and crop production. Throughout, we refer to higher plants and not algae but we concede that similar functions may exist in both.

Green light for the LED-based horticulture revolution

One reason that this topic is so timely is the increasingly novel way in which light-emitting diodes (LEDs) are being used for commercial plant growth and plant research. Owing to their huge capacity for energy savings and programmability (Massa*et al., 2008;*Morrow, 2008), LEDs are fast surpassing conventional horticultural and research grow lights in popularity. Conventional lighting, such as metal halide (MH), high-pressure sodium (HPS), and tube fluorescent (TF) bulbs, give a broad but fixed spectrum, containing large proportions of green, FR, and infra-red (heat) wavelengths that the plant may not use (Fig. 1), often making them highly inefficient, whereas LED lights give the unique option of not only controlling spectral quantity but also quality. However, when replacing broad-band white light spectrum conventional grow lights with narrow waveband LEDs, an understanding of how plants respond to the individual wavelengths is crucial to improving, or at least maintaining, plant quality. Light ‘recipes’ are currently being developed by many companies to create the best light environment for the commercial growth of horticultural plants. The ability to switch rapidly between different irradiance levels and spectra is unique to LEDs and these offer possibilities that have not yet been exploited. For example, by linking the lights to sensors for ambient light and plant physiological status, it should be possible to regulate the output according to the plant photosynthetic requirements. LEDs have high relevance for ‘vertical farming’, a term for a diverse set of technologies that aim to concentrate crop growth with a low land-area footprint, usually in urban areas (Despommier, 2013).

Etc etc

Full review

https://academic.oup.com/jxb/article/68/9/2099/3857754

This is what hps still has on led imo.. that and maybe extra IR..

 

[Ibechillin]

I enjoyed this pdf from hydro grow led, had not heard of them until they started posting here on the forums the last few days.

https://www.hydrogrowled.com/wp-content/uploads/2018/09/X3-for-Download.pdf

The pdf explains the specific wavelengths of light most efficiently utilized by plants are 439nm, 469nm, 525nm, 642nm, 667nm, and 740nm. Also the more efficiently a wavelength is utilized for photosynthesis the faster the chloroplasts become saturated from that color.

This chart explains the ratio of blue, green, red light that had the most overall effect on tomato growth, yield and harvest time. 10% blue, 15% green and 75% red seems optimal and correlates with my own research:

 

[Share_The_Pain]

Hi all, just sharing an article related to the subject...

https://www.royalqueenseeds.com/blo...ht-spectrum-and-ways-to-raise-thc-levels-n269


��️ Peace & love all ��

 

[kukac]

Please if somebody can tell me if this light bulb is any good for veg. I can get some for free


Mh 400w
7500K
Cri 90
25 000 lumen

Thanks

 

[Douglas.Curtis]

https://academic.oup.com/jxb/article/68/9/2099/3857754

This is what hps still has on led imo.. that and maybe extra IR..

You've missed the transition then, yes?

With white LEDs you're getting your 15% green, without the full 30% infra-red tax. Infra-red is also much less expensive with LED than previously, and with better ballast efficiencies, over HID, the LED is a better source.

Even the basic spectrum used by Mars Hydro performs quite well, while the high end gear results are ridiculous. HID/LED differences are not distinguishable by the end user any longer, when grow skills are on point.