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What Is Photosynthesis? From Light Energy to Chemical Energy

An example of photosynthesis is how plants convert sugar and energy from water, air and sunlight into energy to grow.

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Light and dark reactions in photosynthesis - …

by comparing PAR at the same depth (15" of air is the standard). Using LED fixtures of similar lens angles (120/unlensed to 120, 90 to 90, etc.).
Take the input wattage and divide it by the PAR reading. You will find efficiencies as high as .08 watt of input energy per point of PAR in the AAP Reef White NP 2000 LED to as low as 2.7 watt per point of PAR in the Beamswork EA Timer FSPEC LED. Most of the better LEDs are under .30 watt with most falling in the .4 to .50 watt range such as the SB Reef Light

What is light dependent and light independent reactions in photosynthesis.

Based on email I get, forums I regularly read, & YouTube videos (for DIY LED Aquarium Lights), many seem to make this very INCORRECT assumption about emitters, drivers, PWM, wasted heat energy, etc.
This has resulted in a plethora LED lights flooding the market that are non reef capable, marginally reef/planted capable or very reef/planted capable, BUT often requiring 3-4 times the input wattage for EQUAL efficient PAR!
Basically one is back to the high energy input of a MH, but now in a LED.
It is NOT that many of these LEDs cannot keep photosynthetic life as we know these lights can and do quite well from practical experience, these are simply less efficient due to wasted heat energy, use of more of the less efficient, yellow, amber, green, or binned emitters; QUITE SIMPLE!

Light and dark reactions in photosynthesis - eschooltoday

A Couple more points to better explain the concepts of PUR,

Caution as to using Lumens as a useful measurement of Light Output:
While lumens are a important useful measurement for standard household light bulb comparison, it is only a part of the equation for aquarium use, especially when this measurement is applied to new technology lights employed by aquarium keepers (such as LEDs).
As an example of just one aspect where the lumen measurement falls short is when Kelvin is considered; a cool white lamp emitting 1000 lumens at a color temperature of 5,500K will not emit as much PUR as a lamp emitting 1000 lumens at 6,500K.
More over, when compared to "Useful Light Energy" (PUR), Lumen output falls well short as useful comparison of light output.
This said, I am not saying Lumen output and focused lumens are useless, as these parameters are a piece of the light parameter "pie", but often it is overrated and these parameters should only be taken as a part and a small part at that when compared to PAR & PUR.

Focused Lumens;
It is also noteworthy that even the lumen output can be deceiving when considering aquarium lights.
The best LED Lights are a good example of this as these newer technology lights have extremely focused light energy with little essential light energy lost (such as by Restrike), unlike almost every other type of aquarium light currently available.
With this focused energy a "high end" LED often requires half the lumens (or often even less) to provide essential light energy to plants, corals, etc. The newer generation LED lights have considerable less loss of lumens at 20 inches than a CFL light (as per tests that show 166% more lumens for the same wattage LED as compared to a common CFL of equal wattage).

Light and dark reactions in photosynthesis

Watts equal one joule of energy per second. For us, it's a measurement of how much energy our light fixture is using NOT of light output!
This is why the old rule: "3-5 watts per gallon" can be deceiving, and this rule is only a starting point at best. This archaic rule was more accurate when all that was used were T12 lamps which is what this rule is based on.

The international unit of luminous flux or quantity of light used as a measure of the total amount of visible light emitted. The higher the lumens, the "brighter" or more "intense" the light looks to the human eye. You can figure lumens per watt by dividing the lumens your lamp lists by the wattage the fixture lists.

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  • Photosynthesis dictionary definition | photosynthesis …

    How does chlorophyll absorb light energy and pass it on to the energy-requiring reactions of photosynthesis

  • Plant Energy Transformations-Photosynthesis

    Photosynthesis - Part I: The Sun and Light Not all of the light from the Sun makes it to the surface of the Earth

  • NOVA - Official Website | Illuminating Photosynthesis

    An example of photosynthesis is how plants convert sugar and energy from water, air and sunlight into energy to grow.

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Photosynthesis | Definition of Photosynthesis by …

This is another concept to consider that we do not know all the "mechanisms" that drive it.
Basically photoinhibition is the damage to the light harvesting reactions of the photosynthetic capacity of a vascular plant, algae, or cyanobacterium by excess light energy trapped by the chloroplast.
This process can occur in in all organisms capable of oxygenic photosynthesis. In both plants & cyanobacteria, blue light causes photoinhibition more efficiently than other wavelengths of visible light, although it has been demonstrated the red light can cause photoinhibition as well.

Chemistry for Biologists: Photosynthesis

The term "watts per gallon" is getting more archaic with the newer T-2, T-5, CFL, the SHO, & especially the new reef compatible LED lights.
Even within LED Lights, one 30 watt LED is not equal to another 30 watt LED.
An example, you cannot compare a 30 Watt TMC Ocean Blue to a 130 watt EcoTech Radion. However if you were to use an equal wattage of the TMC Ocean Blue or Reef White, you would have more actual useful light energy (PUR) with these per watt of energy used (input energy) than the EcoTech (this is not to say the EcoTech Radion isn't reef capable LED).

Wattage input of lights versus PAR/PUR output is where the actual watts used when comparing one light to another is simply not at all accurate as there is no formula for the PAR or PUR based on input wattage. Keep in mind that PUR has nothing to do with input wattage, and PAR can vary due to light efficiency such fan use (fans waste input energy/watts), lenses, re-strike (in fluorescent lights in particular), and circuitry (such as daisy chaining of emitters common to many discount LEDs).
An example; the Fluval, Finnex & Current Satellite are all discount LEDs that daisy chain their plethora of low quality/output emitters versus LEDs such as th Aqua Illuminations HD, EcoTech, or AAP AquaRay which use advanced circuitry/drivers with a lower number of HO quality emitters.
The result is a much higher PAR output per wattage input. An example would be the Fluval Fresh & Plant 2.0 A3990 which uses 32 watts of input energy with a PAR output about 70 mmol at 400mm. This is .45 watt of input energy per mm of PAR compared to an AquRay NP 2000 at only .08 watt of input energy per point of PAR.

Apples to oranges comparisons of a LED of 75 watts to a T12 cool white Fluorescents also of 75 watts also fails. These cool white T12s will simply not even be close to "useful light energy" output at 75 watts as the LEDs, especially the higher end LEDs).

The bottom line is 'watts per gallon' can be used when comparisons are "apples to apples" such as one Patented High output LED emitter of the SAME BRAND to another, but NOT when comparing a T8, to a T5 to a T2, etc.

photosynthesis notes - Biology Junction

The point this makes/demonstrates is that while both lights are rated as 6500K, they are still not the same in their light energy output. Even among LED lights we can have differences of spectrographs depending upon emitters used.
Think about how mixing all paint colors will produce black, while the mixing of all light energy produces white. We as humans may notice this to some degree, however we do not have the ability to pick out particular colors such as a honey bee can. As well, photosynthetic aquatic life also has differing abilities to pick out the needed light energy for life processes and even though the PAR readings may be equal, the light energy that provides this overall PAR or kelvin "color" is NOT.

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