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Light through the eyes of cannabis


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Ok men and boys, this is not my work, I am just sharing, I will do my best to credit the authour and will provide sorce site.


We all know how important light is to the production of cannabis. In order to optimize the photosynthetic activity of cannabis plants, one must understand how the plant captures and uses light energy to create plant tissues and compounds,such as glucose (for food) and cannabinoids like THC (for us). Light intensity and light quality-i.e., WAVELENGTH- both play an extremely significant role in photosynthesis and cannabis growth. In this article, we will examine how this occurs and which components of plight play the biggest parts.

BY HERB SPADOWSKI, PH.D.

WHAT IS LIGHT:

light has the characcteristics of both a wave and a particle. Figure 1 shows the wavelenght of blue and red light.

The distance between the peaks of the wave is measured in nanometers (nm). As that distance or frequency changes, so does the color of the light. the color red, for example, resides at one end of the visable spectrum and is the result of light with a wavelenghth of 620 to 750 nm. Blue light resides at the opposite end and has a shorter wavelength of 450 to 475 nm. Light is also produced in wavelengths that are out of the visinle range of our eyes, such as ultraviolet (UV) light, and this light also factors into plant processes especially at the end of the flowering period.

Anything that has color or pigments, such as plant leaves, reflect or absorbs light. the light that is reflected off an object hits out eyes, causeing us to see that color. The primary wavelengths of light reflected by cannabis is green, due in large part to pigments such as clorophyll a and b in the leaves; what we don't see as reflected light is mostly absorbed by the leaves. Cannabis leaves absorb most forms of visible light except green and yellow. The majority of the reflected light is green, so the relfected yellow light is not noticeable.

However, leaves can bein to turn yellow if the plants are not healthy. This occers because the unhealthy leaves don't contain enough chlorophyll molecules. Due to the lack of chlorophyll, green light isn' reflected by leaves and yellow becomes the dominat reflected wavelenght.The same phenomenon happens every fall when the leaves of deciduous trees begin to break down chlorophyll. the trees then pull the energy-rich breakdown products out of the leaves before they drop for winter. The result of the lost chlorophyl molecules are the bright reds, oranges and yellows of the fall season.

As stated, light also has the characteristics of a particle. these particles of light are called photons. When the sun is shining or there's a light on, photons of light are pouring down like rain drops. The higher the intensity (strenght) of the light, the greater the quantit of photons emitted; this is why keeping artificial light slose to plant canopies indoors is so vital. Each type of photon has a spesific wavelength that is travels along. so a bulb that is said to be abundant in blue light would emit photons with wavelenghts from 450 to 475 nm.

PHOTOSYNTHETIC PIGMENTS IN CANNABIS:

The amazing thing about plants, including Cannabis, is how they take the energy from photons of light and convert it into molecules of chemical energy. This process is called PHOTOSYNTHESIS, which means "synthesis using light".

During Photosynthesis, cannabis captures photons of light using several diffrent molecules. The primary molecules responsible fo this is Chlorophyl, which occurs in two main forms: chloropyll a and b. Chlorophyll a has a maximum photosyntheic activity when photons of light are at wavelenghts of 430-660 nm while chlorophyll b has a maximum activity at wavelengths of 450 to 640 nm(figure 4). Notice that in figure 4, then the curves for both chlorophyll a and b are in the green-light portion of the graph, their photosynthetic activity decreases greaetly. AGAIN, this is because chlorophyll a and b do not absorb, but rather reflect, green light. it should also be noted that figure 2 depicts the sun's natural spectrum on earth, which shows that wavelengths around 450 nm (blues) and 650 nm(reds)are the least abundant in nature. This has led some scientists to conclude that the reason there's higher absorption activity in at these wavelenghts in because the plants have evolved to become more efficient at processing what is least available to them.

The second most abundant light-absorbing compounds in cannabis are caroteniods, which are also shown in figure 4, carotenoids are inportant for photosynthesis in all plants. Notice they have very low photosynthetic activity in the areas of yellow, orange and red light. In addition to playing a important role in photosynthesis, these compounds are also responsible for the color of yellow flowers, orange carrots and red tomatoes.

THE LIGHT-HARVESTING COMPLEX:

The pigments discussed make up a highly complex structure called the light harvesting or antennae complex, which exists in all plants ( figure 5). this complesx is complesed of about 200 to 300 chlorophyll molecules, numerous carotenoids, and several other light sensitive molecules and imprtant proteins. all of these components are arranged around a central chlorophyll molecule called the reaction center. the reaction center is responsible for the conversion of light energy into chemical energy through the transfer of a single electron.

This process works as follows: When one of the light-sensitive molecules, such as chlorophyll is struck by a photon of light, it enters into an excited state. as it returns back to its normal state, the energy is transferred toward the reaction center. It takes many photons striking many molecules in the liight-harvesting complex to reach the goal of transferring a single electron to the reaction center. Picture one person trying to push a boulder that will not move; if the number of people pushing that boulder increases, together they will create enough force to roll it. The same action occurs during photosynthesis, whereby energy from a number of light photons is required to create enough energy for the transfer of a single electron. This electron tranfer is the very first chemical step into creation of sugar (glucose) from carbon dioxide (co2) and water (h2o) during photosynthesis. furthermore, this sugar is the primary source of energy for the reactions and biochemical processes that will lead to the glistening, resinous THC glands that top your cannabis buds.

LIGHT INTENSITY:

Now we understand a little bit more about how cannabis plants capture light photons and covert their energy into chemical energy and biomass. How then, as a grower of cannabis, can you maximize plant efficincy and yeilds with commercially available lights? whenit comes to light intensity (i.e., Quantity of light), the answer is pretty simple: morelight. it is difficult to overdo the Quantity of light for Cannabis production (always assuming that you have proper temperature controls in place). Generally, the more lights you have and the more powerful those lights, the better your light intesnsity(though not so much better for your electric bill).

But adding more lamps or using higher wattages isn't the only way to increase light intensity. keeping lamps close to the garden canopy will increases the intensity of light reaching your plants and make more efficient use of the electricity you're paying for. The Inverse-square LAW dictates a specified physical quantity or strength is inversely proportional to the square of the distance from its sorce in the case of light, this basically measn that the strength of the light decreases exponentially with everyfoot of distance between the lamp and your plants

EFFECTS OF LIGHT QUALITY:

The sectral quality of wavelength of light is another important factor when it comes to the productivity and quality of cannabis-AND its; salso one of the most complicated. in many diffrent types of plants, the quality of light can affect such things as disease resistance, plant anatomy and morphology, nuitrient uptake and the formation of secondary compounds( such as THC)

A number of scientific studies have shown that blue light has an influence on the number of chloroplasts (which contain the light-harvesting complex and cholophyll) and the stomatal opening. Stomata are the part of the leaf that controls the gas exchange and therefore how much carbon dioxide is available to the leaf for photosynthesis. Many other studies have showen that plants under white LED (whcih Contain al the colors of the spectrum) grow better then plants under red LED light alone, blue LED light alone or even red and blue LED lights in combination. These studies re-emphasize the importance of full-spectrum light in our gardens.

Another study-this one preformed in indiana university by two researchers named maahlberg and hemphill-tested THC content in the leaves of cannabis plants grown under sunlight, red light, blue light, green light, or complete darkness. The experiment revealed that the plant grown under the sunlight had the highest THC concerntration. The THC concerntration decreased successively in the plants grown under red light blue light and green light; the plants grown in darkness had the lowest thc content. Addintionally , under every light treatment, the researchers found that the leaves receiveding the highest quantitiy of light had the highest concerntration of thc. although the researchers weren't specificall looking to evaluate THC content, they did discover that wavelength, or the spectral quality of the light sorce (i.e.., full spectrum versus a single or limited spectrum), is an important factor for THC production, and also that shading can also lower THC concentrations.

CHOOSING LIGHTS:

With all of this information at hand, choosing a light of combination of lights for growing can be a daunting task. figure 7 shows most of the possibilities of light sources, as welll as the distribution of spectral wavelengths produced by each.

Notice that sunlight has by far the broadest possiable spectrum of light available-for horticultural purposes, its the very definition of full-spectrum light. This characteristic, along with the high intensity and raw power of sunlight, is why this soruce of light is the best for cannabis production... not to mention that is free! But as we all know this isn't always an option, and plants must often be grown indoors underartificial lit conditions. therefore, choosing a combination of lights that matches the spectral ratio of the sun is the best option for you plants

All of the liht sorces shown in figure 7 have been around for some time, with the exception of plasma lights. these are the latest and greatest light sorce for indoor cannabis production and produce a spectrum similar to the sun(bear in mind that sunloight is also plasma light). these lights are also highly energy-efficient. currently, the main problem with plasma lights is their price, which can reach serveral thouasnd dollars. With increasing demand and manufacturing, however, expect these prices to drop over time.

So now you might be asking, "how can i mimic the quality of the sun and efficienttly- at low cost- produce the best cannabis possiable?" Unfortunatly, there is no simple anwser to this. Theres a good deal of anecdotal information all over the internet on which wavelength are best for cannabuss abd THC production, but most of this informatino is not proven and was likely developed underless than-scientific conditions. Think back to the light-harvesting complex: if you're using only red light to grow your plants, there's a lot of light-absorbing molecules that respond to many diffrent wavelengths just sitting around doign nothing. this decreases the effcientcy of your plants' photosynthetic system and production.

This is why, as a grower, you need a system of lights that best mimics the quality of sunlight(while also staying within your budget). Remember to keep your lamps close to the garden canopty and utilze proper ventilation for athosphere and temperture control. Putting lights on light movers -is also a great idea. And supplementing HID lighting with Broader-spectrum lighting will go a long wa towards ensuring that yur plants are happy, healthy and , most importantly, productive HAPPY GROWING..

SEPT 2011 HIGH TIMES

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