# MH or HPS from veg to flower



## robo420 (Aug 20, 2009)

My first grow is almost complete with the old floro junk, and figure for the next one I would like to upgrade the light for my soil grow.  I see some decent priced used Hid's that are in my tiny budget. I understand the way to go is MH for veg, and HPS for flower, and I know there are convertables out there.  If I had to pick one to use from start to finish due to the budget, which one should I go with?


----------



## OGKushman (Aug 20, 2009)

Hps will grow your plants after they get too big for floro's.

then just switch from 18/6 light to 12/12 light...


edit: just re-read the end. HID's will most likely kill seedlings and clones plus the cost of running it during peak hours (18/6) is insane! Use floros until they get too big to grow under them then switch to HPS.


----------



## cubby (Aug 21, 2009)

I've used HPS thru the entire life cycle with excellent results. I have never lost a seedling due to HPS. As far as clones, I can't really say because I've never grown from clones indoors. But it seems to me that if you use common sense, don't put the light too close untill the plants are used to it, then I don't see a problem.


----------



## Mutt (Aug 21, 2009)

I use an MH for flower flos for veg. I used to use a HPS, but i do like the MH better...but thats just me.


----------



## stillsmokin43 (Aug 21, 2009)

let me just stir up some stuff here   i have used MH  start to finish for years  i have since added a HPS in my experience, MH do better they grow tighter buds and the weed is more stoney.  Hps  does add to harvest a little they seem to stretch a bit more and a slightly more airy bud  if your genetics are top notch i dont think it would matter enough to worry about it. As far as (most likely will kill seedlings)  i disagree kushman  not so close at first and then move them in as they get stronger  this works for me it may not for others      just my experience   hope this helps


----------



## OGKushman (Aug 21, 2009)

stillsmokin43 said:
			
		

> let me just stir up some stuff here   i have used MH  start to finish for years  i have since added a HPS in my experience, *MH do better they grow tighter buds and the weed is more stoney.*  Hps  does add to harvest a little they seem to stretch a bit more and a slightly more airy bud  if your genetics are top notch i dont think it would matter enough to worry about it. As far as (most likely will kill seedlings)  i disagree kushman  not so close at first and then move them in as they get stronger  this works for me it may not for others      just my experience   hope this helps


Density relies solely on lumens per area, and of course strain...

Being stonier from using MH? That doesnt follow...?


MY EXPERIENCE WITH A 1000 WATT, has only led to issues of heat and cost to run.

This big lamp forced me to add an air conditioner to the room, vortex fan to cool bulb, energy bill through the roof, and move my plants far away from the light...but rewarded me with the densest tightest packed buds I HAVE SEEN IN SOME TIME, ALONG WITH THE DANKEST AND BIGGEST HARVEST i HAVE EVER HAD.

*dang caps lock



I dont understand why someone would use an HPS on something under a foot tall, big waste of energy to grow such a small plant.  Floros dont require cooling and will grow until HPS are needed. 

Running a HPS exponentially raises your energy bill, causes heat issues, and is  very easy to spot using FLIR. I recommend using it for 12/12 light schedule. 


THIS IS MY OPINION AND IN NO WAY IS FACT, JUST MY EXPERIENCES AS A HOMEOWNER/GROWER for a few years
 

-OGK


----------



## Mutt (Aug 21, 2009)

I don't know about that either as far as potency. I do know some strains prefer the blue light. heavy sats love it.

Quite a few hard core organic guys swear by MH full grow. But on same note same organic guys say that when in chem enviro not as big of an issue as your force feeding the plant. 

I'l have to one day do a comparison grow to check this out.


----------



## robo420 (Aug 21, 2009)

Thank you all for the advice, I may still run the flouro at the begining to save the electircity and all.  As far as the bulb goes, I guess I figured there would be a clearcut winner, right now were 2 and 2 huh?


----------



## Rolling Thunder (Aug 23, 2009)

robo420 said:
			
		

> Thank you all for the advice, I may still run the flouro at the begining to save the electircity and all. As far as the bulb goes, I guess I figured there would be a clearcut winner, right now were 2 and 2 huh?


 
Not that I desire to be the tie-breaker, but I would opt for the HPS "from veg to flower," but with supplemental UVB during the latter stage of the flowering phase. I will say more about that later; but for now, I'd like to post a few interesting (and perhaps not uncontroversial) documents for everyone to read and discuss:- 



*MARIJUANA OPTICS​​**: *An elaboration on the phytochemical process that makes THC - by Joe Knuc​ 
The resin exuded by the glandular trichome forms a sphere (1) that encases the head cells. (2)​ 
When the resin spheres are separated from the dried plant material by electrostatic (3) attraction and placed on a microscope slide illuminated with a 100W incandescent bulb, they appear very dark when observed through a 300X microscope. Since orange, red, and infrared are the component wavelengths of incandescent light, and since the absorption of light makes an object dark or opaque to the frequency of the incoming wave, one can conclude that these wavelengths are probably not directly involved in energizing the cannabinoid pathway. (4)​However, the resin sphere is transparent to ultraviolet radiation. (5)

The author found through trial and error that only one glandular trichome (6) exhibits the phytochemical process that will produce the amount of THC associated with pain relief, appetite stimulation and anti-nausea; euphoria and hallucinations are side-effects, however. This trichome is triggered into growth by either of the two ways that the floral bract is turned into fruit. (7)

Of all the ways that optics are involved in the phytochemical production of THC, the most interesting has to be how the head cells and cannabinoid molecules are tremendously magnified (8) by the resin sphere. These and other facts are curiously absent from the literature. The footnotes update the literature to include electrostatic separation of the resin sphere from the dried plant material and marijuana parthenocarpy.

(1) "For all spheres, a ray drawn perpendicular to the sphere's surface will intersect the center of the sphere, no matter what spot on the surface is picked, and the magnifying power(a) of a glass sphere is greater the smaller its size. A sphere of glass can also bring light that is heading to a focus behind it to a point within it, with freedom from two aberrations, spherial aberration and coma, but not from chromatic aberration. Chromatic aberration results when different wavelengths are focused on different planes and is the most difficult of the aberrations to correct. The human eye lens also exhibits chromatic aberration, but a yellow pigment(b) called the macula lutea in the fovea, an area at the rear of the eyeball, corrects this problem by the way it absorbs blue light."

(a)"The formula to calculate the magnifying power of a sphere is l=333/d, where l is the magnifying power and d is the diameter of the sphere expressed in mm."

(b)Interestingly, the resin exuded by drug-type flowering female marijuana plants has a yellow tint. Could this pigment work to correct chromatic aberration in the resin sphere like the macula lutea does in the fovea for the eyeball?

(2) Quoting from the Mahlberg and Kim study of hemp: "THC accumulated in abundance in the secretory cavity where it was associated with the following: cell walls, surface feature of secretory vesicles, fibrillar material released from disc cell wall, and cuticle. It was not associated with the content of the secretory vesicles."

The resin spheres contain the THC. It is not contained in the leaf or floral bract. After the resin spheres are dissolved in solvent or dislodged by electrostatic attraction, and a microscopic examination of the leaf or floral bract has revealed that only the glandular trichomes' stalks remain, no effect will be felt after smoking the dried plant material from which the resin spheres have been removed.

(3) The electrostatic collection of the resin spheres from dried marijuana plants with plenty of ripe seeds has been for hundreds of years the method indigenous people of North Africa and Lebanon have used to make hashish. Obtain a round metal can 8" or so in diameter x 3" or so in depth (the kind that cookies come in) with a smooth lid. Obtain 2 ounces of dried marijuana with plenty of ripe seeds in the tops. To remove the seeds and stems, sift the marijuana tops through a 10-hole-to-the-inch wire kitchen strainer into the can. Close the can with the lid and vigorously shake the closed can three or four times. This gives the resin spheres an excess negative charge. Let the can sit for a moment and then remove the lid. Opposites attract. The negative-charged resin spheres have been attracted to the metal surface of the can and lid which has a positive charge. Take a matchbook cover or credit card and draw the edge across the surface of the lid. Note the collected powder. Observed under 300X magnification, the collected powder from this "shake" is composed of resin spheres with an occasional non-glandular trichome. As the marijuana is shaken again and again, and more of the yellow resin spheres are removed from the plant material, the collected powder gradually becomes green-colored as the number of non-glandular trichomes increases in the collected powder. The greener the powder, the less the effect.

(4) "Cannabinoids represent a dimer consisting of a terpene and a phenol component. Cannabigerol (CBG) is the first component of the pathway. It undergoes chemical change to form either cannabichromene (CBC), or cannabidiol (CBD). Delta 9-tetrahydrocannabinol (THC) is derived from CBD."

(5) "Pate (1983) indicated that in areas of high ultraviolet radiation exposure, the UVB (280-320 nm) absorption properties of THC may have conferred an evolutionary advantage to Cannabis capable of greater production of this compound from biogenetic precursor CBD. The extent to which this production is also influenced by environmental UVB has also been experimentally determined by Lydon et al. (1987)."

The writer's own experience allow for a more specific conclusion: If the UVB photon is missing from the light stream(a), or the intensity as expressed in µW/cm2 falls below a certain level(b), the phytochemical process will not be completely energized with only UVA photons which are more penetrating but less energetic, and the harvested resin spheres will have mostly precursor compounds and not fully realized THC(c).

(a)Examples of an environment where the UVB photon would be missing from the light stream include all indoor cultivation illuminated by HID bulbs and in glass or corrugated fiberglass covered greenhouses.

(b)"The maximum UVB irradiance near the equator (solar elevation angle less than 25 deg.) under clear, sunny skies is about 250 µW/cm2. It was observed that the daily solar UVB in Riyadh, Saudi Arabia (N24.4Lat.) decreased from September to December by about 40% (Hannan et al. 1984). The further a person is from the tropics, the less UVB radiation there is: the average annual exposure of a person living in Hawaii is approximately four times that of someone living in northern Europe." Below are some UVB readings taken in Hoyleton, Illinois, on a clear sunny day in June by David Krughoff as reported in Reptile Lighting 2000.

7am: 12 microwatts/cm2
8am: 74 microwatts/cm2
9am: 142 microwatts/cm2
10am: 192 microwatts/cm2
11am: 233 microwatts/cm2
12pm: 256 microwatts/cm2
1pm: 269 microwatts/cm2
2pm: 262 microwatts/cm2
3pm: 239 microwatts/cm2
4pm: 187 microwatts/cm2
5pm: 131 microwatts/cm2
6pm: 61 microwatts/cm2

(c)Cannabinoid pathway: Anywhere in this pathway UVB (320 nm - 290 nm) does a better job than UVA (400 nm - 320 nm) in energizing a phytochemical reaction that will produce more fully realized THC because "all cannabinolic compounds show an absorption maximum between 270 and 280 nm in the ultraviolet region."

To be continued in the next post ...


----------



## Rolling Thunder (Aug 23, 2009)

Rolling Thunder said:
			
		

> (c)Cannabinoid pathway: Anywhere in this pathway UVB (320 nm - 290 nm) does a better job than UVA (400 nm - 320 nm) in energizing a phytochemical reaction that will produce more fully realized THC because "all cannabinolic compounds show an absorption maximum between 270 and 280 nm in the ultraviolet region."
> 
> To be continued in the next post ...


 
*Marijuana Optics - the continuation.*

(6) Capitate-stalked glandular trichome.

(7) #1: The ovum has been fertilized and there is a seed developing: In the areas of the Northern Hemisphere where indigenous people have grown heterozygous drug-type marijuana for hundreds of years, pollination is used to trigger the growth of the capitate-stalked glandular trichome on the floral bract and concomitant leaves of the flowering females before the autumnal equinox(a) so the majority of seeds will be ripe(b) before November.

(7) #2: The floral bract has become parthenocarpic: Parthenocarpic fruits develop without fertilization and have no seeds. Except for transmutation and turning lead into gold, there has been more nonsense written about *seedless marijuana* than on any other subject. In marijuana parthenocarpy, the floral bract (the fruit) enlarges in size as though there were a seed growing inside, and the capitate-stalked glandular trichome is triggered into growth on the floral bract and concomitant leaves. "Most popular supermarket tomatoes are parthenocarpic which was induced artificially by the application of dilute hormone sprays (such as auxins) to the flowers." In a trial, marijuana parthenocarpy was not induced by the application of the spray used on tomatoes. Only the photoperiod(c) will trigger parthenocarpy in flowering female marijuana plants. Marijuana parthenocarpy occurring before the autumnal equinox is considered by the author to be "long-day" and marijuana parthenocarpy occurring after the autumnal equinox to be "short-day".

The longest photoperiod that will trigger parthenocarpy in unfertilized flowering homozygous(d) Indica female marijuana plants is 13:00 hours, give or take 15 minutes. This effect can be obtained in the month of August at N35Lat, and because the capitate-stalked glandular trichomes received plenty of UVB during this month at this latitude, the harvested resin spheres had fully realized THC. Rating: euphoria and hallucinations, major appetite boost and pain relief, deep dreamless sleep. These plants seldom grow taller than four feet but potency makes up for the reduced harvest.

The gene pool is heterozygous if a flowering female marijuana plant is not parthenocarpic by the end of the first week in September in the Northern Hemisphere. If this is the case, pollination is used instead of parthenocarpy to trigger the growth of the capitate-stalked glandular trichome before the autumnal equinox to obtain as much fully realized THC as possible in the harvested resin spheres by the time the majority of the seeds are ripe.

The longest photoperiod that will trigger parthenocarpy in unfertilized flowering heterozygous female marijuana plants is 11:00 hours, give or take 15 minutes: This effect can be obtained in the month of November at N35Lat. Because of the low intensity of UVB radiation at this latitude at sea level during November, the harvested resin spheres evidenced only slightly more THC than precursor compounds. Rating: mild to medium euphoria, appetite boost and pain relief, good snooze.

Thai marijuana falls into this 11:00 hour category, and its parthenocarpy is characterized by an inflorescence in which many floral bracts are attached to an elongated meristem. It is these elongated meristems that are harvested to become a THAI STICK. On the other side of the world, Mexican marijuana grown around the same latitudes (Michoacan, Guerrero, Oaxaca) also falls into this short-day parthenocarpic category and the unfertilized marijuana will become "sensimilla" in the 11:00 hour photoperiod which begins in mid-December in that region. The winter sunshine in those latitudes has more UVB intensity than the winter sunshine at N35Lat.

All unfertilized flowering female marijuana plants will become parthenocarpic in a 9:00 hour photoperiod (15:00 hour dark period): This can be obtained in the month of December at N35Lat. At this latitude in this month there is not even enough UVB in sunlight for precursor vitamin D3 to develop in human skin. The phytochemical process will not produce THC whenever the UVB and UVA photons in the light stream fall below a certain level of intensity expressed in µW/cm2. Rating: no effect.

(a)In the Northern Hemisphere above the Tropic of Cancer, the key to all marijuana potency is this: The more days of sunlight the capitate-stalked glandular trichomes' resin spheres accumulate before the autumnal equinox the more fully realized THC.

(b)It is recognized in the indigenous world that drug-type marijuana with a majority of ripe seeds will produce more euphoria, hallucinations, appetite stimulation, pain relief, and sleep aid than with a majority of unripe seeds.

(c)The photoperiodic response is controlled by phytochrome. "Phytochrome is a blue pigment in the leaves and seeds of plants and is found in 2 forms. One form is a blue form(Pfr), which absorbs red light, and the other is a blue-green form(Pr) that absorbs far-red light. Solar energy has 10X more red (660nm) than far-red (730nm) light causing the accumulation of Pfr." The first and last hour of a day's sunlight is mostly red light because of the scattering effect on blue light. "So at the onset of the dark period much of the phytochrome is in the Pfr form. However, Pfr is unstable and returns to phytochrome Pr in the dark." The red light in sunrise returns the Pr to the Pfr form. "Phytochrome Pfr is the active form and controls flowering and germination. It inhibits flowering of short-day plants (the long night period is required for the conversion of Pfr to Pr) and promotes flowering of long day plants."

(d)In Nepal and nearby areas of India where the capitate-stalked glandular trichome is triggered into growth by parthenocarpy rather than by fertilized ovum, great care is taken to make sure that all male marijuana plants are destroyed as soon as they reveal their sex. This is because unfertilized Indica flowering females can have both stigma and anther protruding from the floral bract. In the Indica gene pool, female-produced pollen carries an allele for long-day parthenocarpy, and seeds resulting from this female-produced pollen will produce another generation of female plants that will also exhibit long-day parthenocarpy during flowering. But if pollen from male plants is introduced into this gene pool, the resulting seeds will produce a generation of females that will exhibit short-day parthenocarpy instead. The allele for long-day parthenocarpy in the female-produced pollen is carried into the gene pool by self-pollination and cross-pollination, and perhaps homozygous is used too loosely here to describe the genetic result.

(8) It appears that the resin sphere acts as an UVB receptor and magnifying lens. The latter apparently lets it gather in a lot more photons than would otherwise be possible; because a lens also acts as a prism, the resin sphere may prevent some wavelengths from being focused where the phytochemical processes are taking place because they could interfere with the efficiency of the phytochemical process that makes THC.

Joe Knuc is a pseudonym. If the paragraph or sentence in Marijuana Optics has quotes around it, then somebody probably with a degree wrote it. As for the rest, it was all written by Joe Knuc and the views expressed are his alone except where indicated.

Copyright (c) 2002 (rev. 2006) Joe Knuc


----------



## Rolling Thunder (Aug 23, 2009)

Shinji TAZAWA 

Light Source Division, Iwasaki Electric Co., Ltd.
(Gyoda, Saitama, 361-0021 Japan)

---Abstract-------------

In Part 1 of this report, we introduced fundamental aspects of the use of artificial light in horticulture, giving an outline of a number of different artificial light sources and discussing recent research trends(such as the use of microwave-powered lamps, light-emitting diode and laser diode devices) in Japan.

Discipline: Agricultural facilities/Crop production/Horticulture
Additional key words: artificial light source, supplemental lighting, plant factory
< url removed >
1...32):References

(Received for publication, December 18, 1998)

---Introduction-------------

Most terrestrial plants grow by selective absorption of natural light from the sun. In plant factories and indoor living spaces, artificial light is necessary as a source of light energy. Therefore, it is necessary to develop technologies to control the light environment and provide effective and economical irradiation for plants. Part 1 of this report covers basic issues related to plant growth and light.

---Wavelengths for effective plant growth---------------

Solar radiation is subject to extensive scattering and absorption by the atmosphere before it reaches the surface of the earth. Direct solar radiation has wavelengths ranging from 300 to 3,000 nm, and is divided into 3 bands: ultraviolet radiation, visible radiation and infrared radiation. The wavelengths of visible radiation for humans are in the range from 380 to 780 nm, and the peak of the visibility curve(photopic vision) is at 555 nm. Similarly, plants have a range of wavelengths that are physiologically effective. There are 2 types of effective radiation for plants: physiologically active radiation and photosynthetically active radiation(PAR). These 2 types of radiation, ranging from 300 to 800 nm, are physiologically effective in photosynthesis, pigment biosynthesis, photoperiodism, phototropism and photomorphogenesis8).

Physiologically active radiation is divided into 5 wavebands: near ultraviolet light(UV)300-400 nm, blue light(B)400-500 nm, green light(G)500-600 nm, red light(R)600-700 nm, and far-red light(FR)700-800 nm (Fig. 1(20KB)) . Photosynthesis, which uses PAR(waveband 400 to 700 nm), requires an energy source with high intensity. The units of PAR radiation are expressed as total photon fluxes in this waveband, since this radiation induces chemical reactions. The total energy emitted from the light source is designated as photosynthetic photon flux(PPF). On the other hand, the energy actually received by plants is designated as photosynthetic photon flux density(PPFD), and its S. I. units are expressed as ?mol?m-2?sec-1 . Although quantum sensors are preferable for measuring the photon flux, because of their high cost, radiation is often measured by PPFD with conversion factors for illuminance.

---Light intensity suitable for photosynthesis--------------

Light intensity suitable for photosynthesis depends on the light adaptation and acclimation properties of the plants, which in turn depend on the environment of their place of origin. The effect of the light intensity can be estimated to some extent by changes in morphology. Generally, plants which grow in the shade or at low light intensities (shade plants) have large, and thin leaves. Inside their leaves, parenchymatous cells do not adequately develop, resulting in an increase of the development of the grana structure and of the chlorophyll content in chloroplasts. The same morphological changes also occur with exposure to red light. On the other hand, plants which grow at high light intensities (sun plants) have thick leaves. Inside their leaves, parenchymatous cells are remarkably developed, resulting in a lower development of the grana structure. However, many enzymes important for photosynthesis can be observed. The same morphological changes occur with exposure to blue light. These differences in the morphology can also be observed in a single plant. Leaves that grow at low light intensities are referred to as shade leaves, and leaves that grow at high light intensities are referred to as sun leaves. Accordingly, leaves in the upper and lower parts of trees have different photosynthetic capabilities9). Morphological adaptation through changes of the light environment is related to the speed of photosynthesis. Plants growing at high light intensities (for example, watermelons, tomatoes, cucumbers, melons and C4 plants)have high saturation points, and they show a maximum photosynthetic rate at the light saturation point. Therefore, a large amount of light energy is required to cultivate plants that grow better at high light intensities. Fig.2(21KB) was obtained by measuring the absorption and release of carbon dioxide during photosynthesis, and indicates the light adaption capability for photosynthesis. When the light intensity is low, the amount of carbon dioxide released by plant respiration is higher than the amount of that absorbed for photosynthesis, resulting in a net release of carbon dioxide. As the light intensity increases, absorbed and released amounts of carbon dioxide change and reach an equilibrium at point A where a net release of carbon dioxide is no longer observed. This point is referred to as the compensation point. If the light intensity increases further, the amount absorbed reaches point B. This point is the saturation point. A suitable light intensity can be determined somewhere between these points A and B according to the particular requirements. On the other hand, since plants that grow under a low light energy (for example, lettuce, Cryptotaenia japonica , herbage crops, and most of the indoor ornamental plants) have low saturation and compensation points, it is relatively easy to cultivate them, to provide them with supplemental lighting and to maintain growth with artificial lighting. Table 1(77KB) shows the saturation and compensation points of major crops, and Table 2(109KB) shows the saturation and compensation points of ornamental plants. Indoor ornamental plants, most of which are derived from jungle undergrowth, can maintain growth at a relatively low light intensity.

In cultivation facilities for plants utilized for salad, and lettuce in closed-system type plant factories in Japan, a light intensity of about 300 to 400 ?mol?m-2?sec-1 is used. Factories where a higher light intensity is needed are hybrid type plant factories where supplemental lighting of 100 to 150 ?mol?m-2?sec-1 is provided. For indoor ornamental plants, supplemental lighting of 10 to 50 ?mol?m-2?sec-1, depending on the variety, has been gradually employed.

---Photosynthesis action spectrum--------------

The efficiency of plant photosynthesis is not the same throughout the 400 to 700 nm waveband. Just as human eyes have visual curves, plants have sensitivity curves over a wide range. Plants select effective wavelengths from white light and utilize them. Fig. 3(21KB) shows the photosynthesis action spectra described by Inada(1976)7) . Curve 1 shows the average values for 26 species of herbaceous plants, and curve 2 shows the average values for arboreous plants. Fig. 4(21KB) shows the photosynthesis action spectra described by McCree(1972)14) . Curve 1 shows the average values for 20 species of plants in chambers, and curve 2 shows the average values for 8 species of plants in fields. The sample plants used are listed in Table 3 . Each of these 4 photosynthesis action spectra has a large peak composed of 2 peaks at about 675 and 625 nm in the red light region, and a small peak between 440 and 450 nm. All 4 photosynthesis action spectra show that red light has a strong action and blue light a weak action. Fig. 5(18KB) shows the average values for the 4 photosynthesis action spectra, and is used to evaluate light sources for plant growth.

Table 3. Plant materials used for the determination of photosynthesis action spectra

Plants Species

Inada 1. (26 species of
herbaceous plants,
1976)

rice, maize, wheat, barley, oat, soybean, peanut, kidney, bean, pea, cabbage, turnip, radish, tomato, eggplant, cucumber, squash, lettuce, garland, chrysanthemum, spinach, onion, sugar beet, sweet potato, perilla, buckwheat, strawberry

India 2. (7 species of arboreous plants, 1976)

peach, Japanese pear, grape, satsuma mandarin, tea, Japanese black pine, ginkgo

McCree 1. (20 species tested in chamber, 1972)

Maize, sorghum, wheat, oat, barley, secalotricum, sunflower, soybean, tampala, peanut, lettuce, tomato, radish, cabbage, cucumber, oriental melon, squash, clover, sugar beet, castor-oil plant

McCree 2. (8 species tested in field, 1972)

Maize, wheat, oat, secalotricum, rice, sunflower, squash, cotton

----Photomorphogenesis----------------

Light acts on plant morphogenesis, including germination, flowering, stem growth, and leaf opening. Light is also a source of stimuli or information in different ways depending on the plant species and the stage of growth. In general, light with blue, red, and far-red components acts on plants. Table 4(57KB) shows the action of each range of wavelengths31).


----------



## Rolling Thunder (Aug 23, 2009)

Rolling Thunder said:
			
		

> ----Photomorphogenesis----------------
> 
> Light acts on plant morphogenesis, including germination, flowering, stem growth, and leaf opening. Light is also a source of stimuli or information in different ways depending on the plant species and the stage of growth. In general, light with blue, red, and far-red components acts on plants. Table 4(57KB) shows the action of each range of wavelengths31).


 
Among these actions, the red and far-red reversible reaction of phytochrome (a photoreceptor involved in seed germination) is particularly well known. In the reaction, the promotive effect of germination by red light(660 nm) irradiation is cancelled out by far-red light(730 nm) irradiation. That is, the effect of the previously irradiated light appears when red and far-red light is irradiated alternately. High intensity blue light and low intensity red light induce strong control of internodal growth. It is well known that with combined irradiation, far-red light is necessary, and that the ratio of red to far-red light controls internodal growth12,15,17) . In addition, blue or high energy light promotes the growth of sun leaves, and red or low energy light promotes the growth of shade leaves. Daylength controls flowerbud formation (photoperiod). Plants are generally divided by daylength into 3 groups in which flowerbud formation is differentiated by specific daytime length: short-day plants, long-day plants, and intermediate-day plants. In flowerbud formation, light acts as a stimulus, with red light, far-red light or blue light being particularly effective, depending on the plant species. Besides photomorphogenesis, blue light with a wavelength of 500 nm or less acts phototropically, and blue light also acts on stomatal movement.

---Artificial light sources for plant growth--------------

The artificial light sources shown in Fig. 6(40KB) can be divided into 2 systems: thermal radiation and luminescence. Among these light sources, 6 light sources which are actually used for plant growth are incandescent lamps, high pressure mercury fluorescent lamps, self-ballasted mercury lamps, metal halide lamps, high pressure sodium lamps and fluorescent lamps. Also, xenon lamps and low pressure sodium lamps are used for research. Fig.7(56KB) shows the energy spectrum of each lamp, and Table 5(73KB) shows the radiant energy balance and reduced values of PPFD per 1,000 lx in the 400 to 700 nm waveband.

1) Incandescent lamps (IL)

Incandescent lamps radiate visible light by thermal radiation generated from tungsten filaments heated to a high temperature by an electric current. The energy distribution is continuous, but the intensity of red light is higher than that of blue light, which possibly leads to intercalary plant growth. Therefore, these lamps are not suitable for photosynthesis. Furthermore, since they have a low light conversion efficiency of around 10 lm/W, as well as high thermal radiation, they are not used for the cultivation of plants. These lamps are used mainly to control photomorphogenesis, and for example, in some factories they are used to control the flowering of chrysanthemums under low light intensities, to prevent dormancy of strawberries and to promote germination.

2) Fluorescent lamps (FL)

Fluorescent lamps are low-pressure mercury vapor discharge lamps with a hot cathode. Ultraviolet light generated by the discharge is transduced to visible light by phosphor coating on the inside of a glass tube. These lamps easily provide the required radiant energy by use of an appropriately selected phosphor, but cannot provide sufficiently high energy light on their own for cultivation. These lamps are often used to grow seedlings in plant factories. Fluorescent lamps for plants are used not only as supplemental lighting for ornamental plants in flower shops but also for tissue culture, especially for plant growth. In addition, a plant factory system has recently been developed, in which an average value of 650 ?mol?m-2?sec-1 can be achieved by employing a total lamp system where a 110 W 3-band fluorescent lamp irradiates cultivated plants at a distance of 30 cm6) . Furthermore, the compact fluorescent lamp has become popular, and is able to provide local supplemental lighting to indoor ornamental plants by recessed lights.

3) High pressure mercury fluorescent lamps (HPMVL, phosphor-coated type)

HPMVLs are based on the principle that the luminous efficiency of sources is enhanced when the vapor pressure of mercury is increased. These lamps are the most stable lamps, and have been used for many years to grow plants. They provide light composed mainly of the radiation line spectrum of mercury, that is, the light lacks the red light component. These lamps therefore enable to control plant growth. To compensate for the lack of red light, a phosphor lamp which provides red light was developed. The efficiency of this lamp is around 60 lm/W. It has been used for many years in foreign countries to provide supplemental lighting and lengthening of daytime. Two types of lamps are available: a clear bulb type and a phosphor-coated type. The phosphor-coated type is a type of fluorescent lamp. The phosphor-coated type is further classified into 2 types: the X type for general use, and the XW type, which compensates for the missing red light component. The range of this lamp is from 50 to 2,000 W. Regarding the outer bulb shape of this lamp, a BT type and an R type are available.

4) Self-ballasted mercury lamps (SBML)

In SBMLs, the arc tube is connected in series to the tungsten filament as a ballast. These lamps compensate for the red light component, which high pressure mercury vapor lamps lack. They provide a good spectral distribution, but since the efficiency is as low as 20 to 27 lm/W, they are used as supplemental lighting for ornamental plants. For plants, lamps where the input ratio of the arc tube of mercury lamps to that of the tungsten filament is adjusted are also available. Two types of outer bulbs are available: a clear bulb type and a fluorescent type. A BT type and an R type for the outer bulb form of this lamp are available. The lamps can be selected in the range from 100 to 750 W.

5) Metal halide lamps(MHL)

The structure of metal halide lamps is based on that of mercury lamps, but they contain various halide additives. There is a wide selection available, including lamps mainly with line spectra and lamps mainly with continuous spectra. The efficiency of MHLs is around 100 lm/W, and they provide light with a reduced red light component above 600 nm. Therefore they are used in plant factories in combination with high pressure sodium lamps. MHLs on their own are used for supplemental lighting in greenhouses, and high color rendition type MHLs which provide light with a spectrum distribution similar to that of natural daylight are used in hybrid type plants factories and growth chambers. Recently, high color rendering index types(70 to 150 W) have gradually been used for supplemental lighting and display lighting for indoor ornamental plants20). Murakami et al.18) carried out research on high color rendering MHLs containing Dy, Nd, Cs, In, Tl, and Na for use in horticulture. Two types of these lamps are available: a high efficiency lamp with a built-in starter and a high color rendition type. BT, T and R types (only for high color rendition lamps) for outer bulb shapes are available. The lamps can be selected in the range from 70 W and 2,000 W. Typical additives are as follows: indium(blue light), thallium(green light), sodium(yellow light), and lithium(red light).

6) High pressure sodium lamps(HPSL)

HPSLs use alumina ceramic for the arc tube, and in the arc tube, sodium and mercury from an amalgam acting as a buffer gas are enclosed. Neon-argon penning gas is also sealed in the arc tube to help starting. The efficiency of some of these lamps exceeds 150 lm/W. Since they have a large red light component which can cause intercalary growth, they are used with metal halide lamps which provide compensating blue light. These lamps are used on their own to cultivate herbage crops with green leaves. These lamps are used solely in hybrid type plants factories. Three types are available: a high efficiency type with a built-in starter, an improved color type with a built-in starter, and a high color rendition type. BT type, T type and R type for outer bulb shapes are available. The lamps can be selected in the range from 50 to 940 W. A lamp in which the lack of blue light component is compensated by the addition of sealed mercury has recently been developed for plants. Inagaki et al.10)developed a high pressure sodium lamp with an output of 1.2 kW and an efficiency of 180 lm/W. Xenon, an inert gas for starter assistance, was sealed in the double-end type lamp at nearly three times the normal pressure.
7) Research trends

(a) Electrodeless discharge lamps(Microwave-powered lamps)

There are several designs of electrodeless discharge lamps depending on the method of illumination, with the microwave-powered lamp being the most promising future development for use in horticulture. Until now, microwave-powered lamps have solely been used for ultraviolet curing in photoengraving processes. Research is currently being conducted on the application of high intensities(130 lm/W, 1,000?mol?m-2?sec-1) which could be achieved by the variation of the sealed gas13). The next challenge facing microwave-powered lamps would concern the production cost and the life-span of magnetrons. Fig. 8(31KB) shows the structure of a microwave-powered lamp and emission spectrum.

To be continued in next post ...


----------



## Rolling Thunder (Aug 23, 2009)

Rolling Thunder said:
			
		

> 6) High pressure sodium lamps(HPSL)
> 
> HPSLs use alumina ceramic for the arc tube, and in the arc tube, sodium and mercury from an amalgam acting as a buffer gas are enclosed. Neon-argon penning gas is also sealed in the arc tube to help starting. The efficiency of some of these lamps exceeds 150 lm/W. Since they have a large red light component which can cause intercalary growth, they are used with metal halide lamps which provide compensating blue light. These lamps are used on their own to cultivate herbage crops with green leaves. These lamps are used solely in hybrid type plants factories. Three types are available: a high efficiency type with a built-in starter, an improved color type with a built-in starter, and a high color rendition type. BT type, T type and R type for outer bulb shapes are available. The lamps can be selected in the range from 50 to 940 W. A lamp in which the lack of blue light component is compensated by the addition of sealed mercury has recently been developed for plants. Inagaki et al.10)developed a high pressure sodium lamp with an output of 1.2 kW and an efficiency of 180 lm/W. Xenon, an inert gas for starter assistance, was sealed in the double-end type lamp at nearly three times the normal pressure.
> 7) Research trends
> ...


 
(b) Light-emitting diode devices(LED)

LEDs are light-emitting semiconductors with uses ranging from simple indicator lamps to more complicated bar and numeric displays, where the development of the blue LED leads to the practical use of full color displays. The LED is a remarkable evolving technical invention. When current flows through the p-n junction of compound semiconductors consisting of Gap(gallium phosphide) or GaAsP(gallium arsenide phosphide), light is emitted as a result of electrons recombining with holes near the p-n junction. The characteristics of LEDs are as follows: low voltage operation, low heat emission, a compact and lightweight design, lack of noise(electron discharge tubes produce noise) and easy control. Horticultural applications are being considered for plant cultivation in space32). In this application, an irradiation source(surface) consisting of a bundle of LED devices irradiates the plant at a close proximity, moving with the plant as it grows. At a distance of 1 cm, a 5,000 mcd, 660 nm LED is able to produce an intensity of almost 50,000 lx. In addition, a combination of red, green and blue devices together with lighting control can produce a balance that is compatible with photosynthesis. The next challenge facing LEDs concerns the production cost and the heating effects resulting from the concentrated use of LED devices. Fig. 9(13KB) shows the structure of a LED device23) and Fig. 10(( shows the spectral distribution in composite lighting. Table 6 shows the characteristics of red, green and blue LED devices21).

c) Laser diode devices(LD)

LDs are light-emitting semiconductors like LEDs. LDs are mainly used in bar-code readers, writeable compact disks(CD), mini disks(MD), compact disk read only memory(CDROM), optical communication transmission, and photocopiers or optical printers. The operation principle of an LD is equivalent to that of laser oscillation. Light emitted from an LED is reflected by a mirror and amplified by stimulated emission. The light is finally emitted through the mirror surface. Fig. 11(24KB) shows a simple LD structure22). Table 7 shows the wavelengths produced by several kinds of LDs22). Takatsuji & Yamanaka24) investigated the possibility of using LDs as light sources in greenhouses since the photo-electronic transducer efficiency of LDs is very high. Results showed that irradiation combined with red and blue LD light pulses was a promising future development in view of the production cost. In addition, Takatsuji & Mori25) confirmed the growth of lettuce using mixed light irradiation(PPFD: 50?mol?m-2?sec-1)of red LD(660 nm)and blue LED(450 nm).

Tsuchiya et al.28) developed an LD6500 with a wavelength of 680 nm and output of 200 nW. A 35% photoelectric transducer efficiency was achieved (theor3200etical maximum 60%). Results of tests carried out on lettuce at 200?mol?m-2?sec-1 PPFD showed that growth was slow. The leaves were thin, presumably due to the use of monochromatic and coherent light. In the mixed irradiation test using red LDs and blue fluorescent lamps(about 6%), plants showed an increased weight and a normal leaf shape, confirming the effect of blue light29). Mori & Takatsuji.16) cultivated lettuce by irradiating light from different kinds of LEDs and red LDs(650 nm) alone or in combination(PPFD: 50?mol?m-2?sec-1 ) and found that the growth was poor in cases where only red LD irradiation was used. This effect was considered to be due to the monochromatic characteristic of red LD light. The following problems in the application of LDs are as follows: sensitivity to electrostatic and current surges, wavelength increase of about 10 nm as the temperature rises, and need for development of a blue light LD.

---Conclusion-----------------

Two main requirements dominate the utilization of artificial light sources in horticulture in both gardens and commercial greenhouses, the first being efficiency. High pressure sodium lamps are generally adopted to offer the highest efficiency in terms of plant growth rate and economy. However, to remain within current standards of farm products(such as leaf greenness and coloration, internode length, stem diameter, and leaf thickness), combination with metal halide lamps is recommended. The second requirement is related to the esthetic improvement of store or house environments, where the primary concern is not growth but maintenance of a plant's natural appearance. High efficiency is not a prerequisite, but the light quality balance becomes important in order to bring out the essential color characteristics of plants and flowers as well as maintaining plant health. To meet these requirements, high color rendering index type MHLs are recommended. Current horticultural research trends lead to the development of 1.2 kW HPSL, 180 lm/W, LED and LD devices for use in commercial greenhouses and the application of microwave and 400 W MHL lamps in growth chambers. [THE END OF PART 1]


----------



## Rolling Thunder (Aug 23, 2009)

Rolling Thunder said:
			
		

> Conclusion of Part 1
> 
> Two main requirements dominate the utilization of artificial light sources in horticulture in both gardens and commercial greenhouses, the first being efficiency. High pressure sodium lamps are generally adopted to offer the highest efficiency in terms of plant growth rate and economy. However, to remain within current standards of farm products(such as leaf greenness and coloration, internode length, stem diameter, and leaf thickness), combination with metal halide lamps is recommended. The second requirement is related to the esthetic improvement of store or house environments, where the primary concern is not growth but maintenance of a plant's natural appearance. High efficiency is not a prerequisite, but the light quality balance becomes important in order to bring out the essential color characteristics of plants and flowers as well as maintaining plant health. To meet these requirements, high color rendering index type MHLs are recommended. Current horticultural research trends lead to the development of 1.2 kW HPSL, 180 lm/W, LED and LD devices for use in commercial greenhouses and the application of microwave and 400 W MHL lamps in growth chambers.


 
Effects of Various Radiant Sources on Plant Growth - Part 2A

by Shinji TAZAWA

Light Source Division, Iwasaki Electric Co., Ltd.
(Gyoda, Saitama, 361-0021 Japan)

---Abstract--------------

In Part 2 of this report, we analyzed the spectrum distribution of several high intensity discharge lamps, in which the spectrum values were multiplied by the average values for 4 different photosynthesis curves developed by McCree(1972) and Inada(1976), and we calculated the photoelectric conversion efficiency expressed as the plant growth radiant efficiency. As a result, we confirmed the high effectiveness of high pressure sodium lamps for plant growth within the PAR range of wavelengths, and concluded that a metal halide lamp 3,500 K(150 W high color rendering index type) was a suitable light source for indoor maintenance of ornamental plants. We also analyzed the light quality balance within the PAR range of different artificial light sources, by using the R/B and R/FR ratios as a reference to photomorphogenesis.

Discipline: Agricultural facilities/Crop production/Horticulture
Additional key words: artificial light source, supplemental lighting, plant factory

1....5):References

(Received for publication, December 18, 1998)

---Introduction--------------

Part 2 of this report deals with an evaluation of various radiant sources for plant growth and the quality of the light balance.

---Evaluation of various radiant sources for plant growth--------------

Broadly speaking, 2 aspects must be considered in the evaluation of radiant sources for plant growth. The first is the efficiency of light energy transformation which is expressed by the ratio of the radiant energy of a lamp to the effective light energy for photosynthesis. This efficiency is a measure of how close the spectral distribution of a light source is to the photosynthesis action spectrum of the plants. To obtain this efficiency, the value for spectral distribution of a light source is multiplied by the sensitivity of the photosynthesis action spectrum of the plants, and then divided by the input power of the light source used. However, it is virtually impossible to analyze the photosynthesis action spectra of hundreds of thousands of plants on the earth. Therefore only the main typical species are used to calculate the efficiency. The quantum sensor, in which the sensitivity is close to the photosynthesis action spectrum, is considered to be a suitable device for measuring the efficiency. Fig. 1(23KB) shows the curve of luminous efficiency and quantum sensitivity. The second aspect to be considered is the quality of the light balance. In general, it is recognized that light with a large red light component promotes intercalary growth, and that light with a large blue light component controls plant growth. The ratio of blue, green and red light components controls plant growth. The ratio of blue, green and red light components in PAR radiation is the key factor determining plant growth. In addition, the ratio of red light and far-red light is an important factor in the elongation of plants.

1) Evaluation of light energy transformation efficiency

To obtain the light energy transformation efficiency, the radiant energy of the light source is multiplied by either the quantum sensitivity or the operational sensitivity of photosynthesis, then divided by the input power of the lamp. Equations used to calculate the light energy transformation efficiency of the light sources are shown below(Eqns. 1 to 3).

Radiant energy of artificial light source;

Radiant energy x quantum sensitivity;

Radiant energy x average sensitivity of photosynthesis spectra ;

o(Éj: spectrum distribution,
p(Éj: quantum sensitivity,
r(Éj: average sensitivity of photosynthesis action spectra, 
oin : input power of lamp.

Table 1(52KB) shows the radiant energy and light energy transformation efficiency of various 660 to 1,000 W high intensity discharge lamps(HID lamps) used in closed system plant factories. Line (1) in Table 1 shows the transformation efficiency to visible light from electric energy supplied by actual light sources as radiant energy. Line (2) shows the light transformation efficiency multiplied by the quantum sensitivity for evaluating measurements. Line (3) shows the efficiency of light energy transformation actually used, which is calculated from the efficiency of light energy transformation multiplied by the average sensitivity of the photosynthesis action spectra of 33 plant species examined by Inada(1976)2) and 28 by McCree(1972)4). As shown in Table 1, from the standpoint of photosynthesis sensitivity and quantum sensitivity, the most effective lamp for plant growth is the HPSL, in which the red light component is large and the efficiency of light energy transformation is high. However, normal growth cannot be expected with a light with a large red light component only. That is, an adequate balance with blue and green light is also necessary.

Table 2 (61KB) shows the efficiency of light energy transformation of 400 W HIDLs used in hybrid type plant factories and in greenhouses for supplemental lighting. Compared with HPMVL, MHL and HPSL show a higher efficiency. In addition, comparison of Tables 1 and 2, shows that high-wattage type HPSLs have a higher efficiency than 400 W HPLSs, and 400 W MHLs have a higher efficiency than high-wattage type MHLs.

Table 3 (46KB) shows the efficiency of light energy transformation of compact type HID lamps installed for indoor ornamental plants. All MHLs have a high efficiency of light energy transformation, as shown in Table 3. In particular, the 150 W 4,500 K lamp shows the highest efficiency, based on the multiplication with the average photosynthesis sensitivity. 

2) Evaluation of quality of light balance 

Evaluation of the quality of the light balance involves the determination of the relative balance of blue light, green light, and red light in the effective radiation range of photosynthesis. Among these, the balance of red light and blue light(R/B ratio) is a typical factor for consideration. High R/B ratio, depending on the light quantity, is associated with intercalary growth of the internodes, and a low R/B ratio is associated with growth control, i.e. suppression of elongation, and production of thick, strong leaves. Table 4(41KB) shows the quality of the light balance of various kinds of photosynthesis action spectra and quantum sensitivities. Considering quantum sensitivity as an indicator, an effective light balance is represented by an R/B ratio of 1.44, obtained with 27.3% blue light, 33.3% green light and 39.4% red light. The average quality of the light balance of 4 photosynthesis action spectra includes 23.5% blue light, 32.0% green light and 44.5% red light. From these values, the R/B ratio is calculated to be 2.71, indicating that light with a large red light component is effective. However, studies carried out by Inada & Yabumoto3) using lettuce and radish, showed that an R/B ratio of 10 or higher was effective for cultivation. Takatsuji et al.5) irradiated lettuce with red LED(660 nm, half wavelength about 30 nm)and blue LED(450 nm, half wavelength about 70 nm)and showed that an R/B ratio of 10 was effective.


----------



## Rolling Thunder (Aug 23, 2009)

Rolling Thunder said:
			
		

> 2) Evaluation of quality of light balance
> 
> Evaluation of the quality of the light balance involves the determination of the relative balance of blue light, green light, and red light in the effective radiation range of photosynthesis. Among these, the balance of red light and blue light(R/B ratio) is a typical factor for consideration. High R/B ratio, depending on the light quantity, is associated with intercalary growth of the internodes, and a low R/B ratio is associated with growth control, i.e. suppression of elongation, and production of thick, strong leaves. Table 4(41KB) shows the quality of the light balance of various kinds of photosynthesis action spectra and quantum sensitivities. Considering quantum sensitivity as an indicator, an effective light balance is represented by an R/B ratio of 1.44, obtained with 27.3% blue light, 33.3% green light and 39.4% red light. The average quality of the light balance of 4 photosynthesis action spectra includes 23.5% blue light, 32.0% green light and 44.5% red light. From these values, the R/B ratio is calculated to be 2.71, indicating that light with a large red light component is effective. However, studies carried out by Inada & Yabumoto3) using lettuce and radish, showed that an R/B ratio of 10 or higher was effective for cultivation. Takatsuji et al.5) irradiated lettuce with red LED(660 nm, half wavelength about 30 nm)and blue LED(450 nm, half wavelength about 70 nm)and showed that an R/B ratio of 10 was effective.


 
Another factor for the evaluation is the photomorphogenesis reaction discussed in Section 5(Part 1). Based on the red light to far-red light ratio(R/FR ratio) it can be determined whether plants will have elongated or controlled growth. High R/FR values indicate controlled growth, and low values indicate elongated growth. The R/FR ratio is calculated by multiplying the light spectrum distribution by the quantum sensitivity. Inada & Yabumoto3) using lettuce and radish, showed that an R/FR ratio between 1.00 to 2.00 was effective for cultivation. Horaguchi et al.1), who cultivated lettuce and sunflower using irradiation from several 4-band fluorescent lamps where an FR light was added to 3-band fluorescent lamps, showed that an R/FR ratio of 0.78 was effective. In general, the wavelength ranges are broadly defined as 600 to 700 nm for red light and 700 to 800 nm for far-red light. Equation (4) is used for the calculation of the R/FR ratio as follows;

R/FR ratio : 

Table 5 (42KB) shows the quality of the light balance, R/B ratio and R/FR ratio of various HID lamps(660 to 1,000 W). The light balance is adjusted on the basis of the visibility curve for human eyes, and therefore tends to contain a large green light component(500 to 600 nm). There is no lamp with an R/B ratio in the range of the quantum sensitivity and the average photosynthesis sensitivity(1.44 to 2.71), except for SBML that shows a low efficiency of light energy transformation. HPSLs, which have a large red light component, induce elongated growth, and are therefore used for cultivating herbage crops in plant factories of the closed system type because of their high efficiency. HPMVLs, and MHLs have a large blue light component, and therefore induce growth suppression. However, MHLs are currently the only high wattage lamps that can be used on their own to induce relatively good quality growth. 

Table 6 (58KB) shows the quality of the light balance of radiant energy, R/B ratio and R/FR ratio of various HID lamps(400 W). SBMLs show the optimum R/B ratio, but their R/FR ratio is associated with elongated growth because of the large FR component. The R/B ratios of HPMVL and MHL are associated with growth control, and that of HPSL with growth elongation. The R/FR ratio of the XW type of HPMVL, the MHL and the high color type of HPSL are all associated with growth elongation. 
Table 7(39KB) shows the quality of the light balance, R/B ratio and R/FR ratio of compact type HID lamps for indoor ornamental plants. To achieve adequate growth in indoor shops, MHL 3,500 K may be recommended because of the high R/B ratio, R/FR ratio and light quality balance. For maintenance growth and esthetic displays, MHL 6,500 K can be recommended because it enhances the green color of leaves of ornamental plants. MHL 4,500 K or 6,500 K can be recommended because their R/B ratios are associated with growth control. If HPSL 2,500 K is used, ornamental plants may become overgrown indoors because both the R/B ratio and R/FR ratio lead to the optimum conditions for growth. 

---Conclusion--------------

To compare different artificial light sources, we determined the spectrum distribution of different light sources and multiplied the values by the average values for the photosynthesis curves derived from 4 sets of data to give an efficiency which we designated as the PGRE(plant growth radiant efficiency). As a result, the PGRE of high pressure mercury fluorescent lamps amounted to 8 to 12%, metal halide lamps(MHL) to 17 to 19% and high pressure sodium lamps to about 18 to 32%, respectively. Metal halide lamps were found to be the most efficient. High color rendition type HPSL and SBML gave excellent light quality balance and high R/B and R/FR ratios, but both exhibited a low basic photoelectric conversion efficiency. For the maintenance of ornamental plants, high color rendition type 4,500 K and 6,500 K lamps show a high PGRE and are effective, but we recommend the 3,500 K lamps due to the high light quality balance and R/B and R/FR ratios. However, if the esthetic effects of a certain store atmosphere are required, we may recommend MHL 4,500 K or 6,500 K in terms of color warmth as well as other factors. The HPSL 2,500 K lamps provide the highest combination of light quality balance, R/B and R/FR ratios, and lead to superior plant growth characteristics. Since many factors relating to plant growth and light irradiation remain unclear, we hope that this report will be a useful point of reference for the research and development of artificial light sources for horticultural applications.

---References---------------
1) Horaguchi, K. et al. (1992): Optical radiant environment for indoor plants. Jpn. Matsu****a Electr. Ind. Tech. Rep., 38(6), 627-634 [In Japanese].
2) Inada, K. (1976): Action spectra for photosynthesis in higher plants. Plant & Cell Physiol., 17, 355-365.
3) Inada, K. & Yabumoto, Y. (1989): Effect of light quality, daylength and periodic temperature variation on the growth of lettuce and radish plants. J. Jpn. Crop Sci., 58 (4), 689-694.
4) McCree, K. J. (1972): The action spectrum, absorbance and quantum yield of photosynthesis in crop plants. Agric. Meteorol., 9, 191-216.
5) Takatsuji, M. et al. (1995): Plant growth experiment using visible light-emitting diodes. J. Jpn. ****A, 7 (3), 163-165 [In Japanese].

*:holysheep: HAPPY READIN' TO Y'ALL - PEACE! ~ RT *


----------

