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The Sun and Lights
The noon sunlight in Denver Colorado it is 5,000 foot-candles or 5,000 lumens per square foot. A l,OOO Watt HPS lamp with its very centre 2 feet above a table is shining 5,000 lumens on every square foot of that table. Although this HPS lamp appears to be equal to the Sun, it is not quite the same.
The one thing that sunlight has over artificial light is that sunlight is just as intense at all distances. This is because the sunlight is very powerful and has already travelled some 93 million miles (149 million kilometres) to reach the Earth, so the extra few feet or metres it has to go to reach the bottom of plants do not account for much light intensity loss.
Luckily for outdoor gardeners, the mighty Sun is giving 5,000 lumens per square foot to both the tops and the bottoms of tall trees. But with artificial lights, it is a different story.
The first foot of light below an HID lamp is more intense than sunlight. Unfortunately, artificial light drops off by half with every foot it travels, so at 3 feet, it is only 1/9 the intensity of the first foot.
This is why the bottoms of a 3-foot plant gets only about 10% as much light as the tops. Therefore, the shorter the plants are under the lights, the better they are at receiving the light.
As explained previously, the Sun has a very high light density of 5,000 lumens per square foot--or 5,000 foot-candles. This means that there are lots of photons striking each square foot of leaf surface.
The Difference Between the Sun and Lights
The real difference between the Sun and lights is that the Sun has full spectrum light from red to blue and knows exactly where to tickle the pigments in the plant's leaves to make them grow well.
All artificial lights are missing much of the best light spectrum for plant growth. The best one can do is to find lights that are an acceptable compromise and hope that the plant is co-operative. The truth is that all the HID's are being improved with time and you should experiement to find whick one suits your plant strain.
The best for frequency is a standard incandescent, but it is so inefficient that it is not usable. Luckily, plants are able to make the best of a poor situation and use the fringes of any light given to them.
More Lumens from Different Light Types
The more lumens per square foot shining on plant leaves, the more photons are striking the leaves, and the more sugar the plant can make during photosynthesis. The more sugar available for the plant to use, the more energy and growth the plant produces. The way to get lumens out of a bulb is either to make its filament hotter so it gives off more photons, or to replace that filament with a tube of gas that gets even hotter than the filament when electricity is pushed through it. Heating a filament is very inefficient and needs enormous wattages (volts x amps = watts) to get enough photons to pass through the glass of the bulb. It is more efficient by ionizing gases in little ceramic tubes which heats the gas to many thousands of degrees and pushes out photons about 100 times better than the filaments. ie this is why we use Metal Halide lamps.
The Magic Is Here - Photosynthesis
The leaves perform photosynthesis in a most amazing way. The leaves have special cells in them called pigments. The main pigments are chlorophyll-a, chlorophyll-b, carotene, phycobilin, and phytochrome. Each of these has the ability to absorb a certain frequency of light and extract energy from the light by converting photons to electrons and then sending the electrons to energy centres. If you look at the Spectra of Photosynthesis and Chlorosynthesis graph attached, you will see that plant leaves absorb most colours of light except green light, which is reflected. The main pigments involved in photosynthesis are the chlorophylls. Chlorophyll-a is the primary pigment for photosynthesis, but cellular plants have developed a helper pigment called chlorophyll-b.
The photosynthesis graph shows that photons of many different colours are used in photosynthesis. Different pigments in plants have the ability to use photon energy to excite their electrons into a higher energy state.
The pigments then funnel this higher electron energy from all the different colour photons to a reaction centre that is specifically reactive to light at 680 nm (P680)' This excited P680 splits water (H2O) into oxygen gas (02) and protons (H+). These protons are passed down an assembly line that converts the electron energy to chemical energy in the form of ATP (adenosine triphosphate).
In the advanced cellular plants, there is a second step to this photon energy conversion. A second reaction centre, which is sensitive only to light at 700 nm (P7oo), boosts the electrons a second time to make chemical energy in the form of NADP (nicotinamide adenine dinucleotide phosphate).
At the end of this process, light energy has been trapped and converted to chemical energy, which is the basic energy of all life on earth. Most astoundingly, the newest research has shown that this entire process takes 3-20 trillionths of a second, which would make any computer chip proud.
The light has now converted many photons into usable chemical energy. This chemical energy is now used totally independently in a process called the carbon-fixing reaction, where carbon dioxide (CO2) is split, and the carbon (C) and hydrogen (H) atoms are made into sugars and starches. The best known example of plant sugar is maple syrup, which comes directly out of trees.
Because sugars are energy, the more sugars a plant can make the more a plant will produce. The plant only needs a weak blue light source. The blue light is only indirectly involved in the creation of plant energy as explained previously; however, the plant specifically needs blue light for other functions. Blue light is important in auxin growth reactions--light from 400-500 nm is absorbed by an internal pigment, and this is the most active frequency for auxins. Blue light stimulates the stomata to open, and so does red light.
The Sun has not yet been equalled by artificial lights for full trum. The HID lights have very low 680 / 700 nm peaks. The High Pressure Sodium bulbs have a very strong orange light, and this mostly absorbed by carotenes and phycobilins, and then passed down the line. The problem for the indoor gardener is that no bulbs give enough of the red and far red frequencies with any great strength. The best one can do is to blast the leaves with MH and HPS lights at enormous powers so that there is enough red spilled over to do the job.
As mentioned before, an HID at close range puts out more lumens than the Sun but at many less important frequencies, so large portions of the light are inefficient.
Light Saturation
An individual plant leaf reaches its maximum energy production between 3,000-4,000 lumens. However, because of shading and dense foliage, only its top and outer leaves achieve 3,000- 4,000 lumens.
Under artificial lights, it has been found that if the overall density of light around a plant can be raised to 10,000-20,000 lumens, more leaves in the plant are able to achieve their maximum of 3,000- 4,000 lumens, due to greater light penetration. However, one should not overpower any specific parts of the plant by putting them too close to the light, as this destroys the chlorophyll pigment in the leaves. Leaves have an internal regulating system that increases with lower light density and starts to shut off energy production in higher light density.
The photon side of the carbon-fixing reaction is not temperature dependent, but the non-photon reaction of carbon fixing in C3 plants increases with temperature up to about 30°C (86°F), after which it starts to slow down. During intense photosynthesis, the leaves have to store excess starch in their cells, and then in the dark period, they convert the starch to sugar and ship the energy to the rest of the plant--especially to the roots. In supercharged plants, the leaves and their petioles (leaf stems), as well as the plant branches, become very important storage places as do the roots which grow into enormous bundles because the leaves are producing energy at many times their natural growth.


I hope it helps...... jam them ladies with power light equals mass.....!!!!!!!!!!!
Native¥organicfarmer Reviewed by Native¥organicfarmer on . The basics on lights and chlorophyll, how it works compared to sunlight..... Hello, The Sun and Lights The noon sunlight in Denver Colorado it is 5,000 foot-candles or 5,000 lumens per square foot. A l,OOO Watt HPS lamp with its very centre 2 feet above a table is shining 5,000 lumens on every square foot of that table. Although this HPS lamp appears to be equal to the Sun, it is not quite the same. The one thing that sunlight has over artificial light is that sunlight is just as intense at all distances. This is because the sunlight is very powerful and has Rating: 5