Which wavelengths to choose

[churchhaze]

Less absorbance does not mean the photons are less usable. It just means there's a lower probability they will be absorbed. But if it's not absorbed in one place, it will be absorbed somewhere else... the lower part of the plant!

 

[stardustsailor]

Of course. That was the question. So I will post the answer. But, 1972? There is much more current data.

Instead of eating food to build molecules, plants can take light from the sun and use the energy to convert carbon dioxide from the air into useful molecules! However, the pigment doesn't strongly absorb blue or green light, so plants can't use this energy for photosynthesis. Interestingly, we know this even from the color of plants! White light contains all the colors, and plants appear green because they absorb the red light, leaving what appears to us as green light, to be seen by our eyes! If the light isn't being absorbed by the plant, it can't be used for photosynthesis!

https://www.rollitup.org/t/v-series-tetras.858075/page-3#post-11416006

 

[Doer]

https://www.rollitup.org/t/v-series-tetras.858075/page-3#post-11416006

Great thread! Thanks.

 

[alesh]

What type of math equation did you use to turn Watts per nm (mW ,actually ) into umol/sec ?

The actual equation is PPF = W * λ(nm )/119,708 .
Check the zip folder.
View attachment 3384218

Cheers.


Edit:On second glance .... It seems that there's no discrepancy,actually ...
Something's wrong with the spreadsheet Abiqua is having .
(maybe another one of my stoney mistakes,I can't tell ... ... )
Anyway ,that was an early edition ,which I do not use anymore .

I can see it's spot on with this sheet! I calculated that number to be 119,6265659. Pretty close I'd say. Must be some difference in constants. I used:

 

[Doer]

Damn them. Avogadro and Planck. Will we ever see the end? (quantum joke)

 

[Doer]

Lol yay. You can read. Now do a simple Google search and you'll find the same articles I would link if I gave a shit to argue with your ignorant ass. Seriously, probably in the first five results you'll find the two articles I would link.

Btw. You've only grown for a couple years and only under 1k and cfls? Where did your sense of entitlement come from again? I consider myself still new and growing at my hobby and I've been going at it 3 times longer than you, with 3 times the different amount of equipment. And again, I consider myself low in this community! Ha. Your speaking down to people with 5 times your experience, time and effort put forth to research and results.

And yet you still quote nothing, drama queen. I say that I have some experience and you turn that into a cock wag.

I have more!! you say so. But, so what? Still no botany.

 

[stardustsailor]

Less absorbance does not mean the photons are less usable. It just means there's a lower probability they will be absorbed. But if it's not absorbed in one place, it will be absorbed somewhere else... the lower part of the plant!

YES...


Plants have been involved for some ..million ..of years under the Sun's light.

The two basic photosynthetic pigments ( ChA & ChB ) of higher plants ,are adapted to the Sun's light,regarding
their ABSORPTANCE.
But there are also OTHER photosynthetic mechanisms / substances. (Some not even pigments ,like the LIGHT HARVESTING PROTEIN COMPLEXES I & II ).

Overall ,higher plants all they want is to absorb as much photons as possible.
(Especially the light -needy plants ,those that they produce complex /massive flowers and large fruits.
More energy absorbed = more biomass produced.)

Still ,that does not mean that the absorbed photons are equally able to drive PS .
Blue photons (the most abundant,even in cloudy weather / winter ) ,are the least efficient driving PS.
Actually ,due to their high energy they can harm the plant tissue & DNA .
(Thus the PHOTO-QUENCHING PIGMENTS like the CAROTENOIDS ,
that absorb mostly blue photons and turn the excess energy into HEAT and/or FR light )

Still ,the answer to the enigmatic question of why plants are reflecting some green and not being totally black ,can probably be found in the actual mineral /element that is used to turn photons into electrons ,at the two basic photosynthetic pigments.

" Chlorophyll is a chlorin pigment, which is structurally similar to and produced through the same metabolic pathway as other porphyrin pigments such as heme. At the center of the chlorin ring is a magnesium ion. "
http://en.wikipedia.org/wiki/Chlorophyll
Magnesium ( Mg ) is quite abundant in ( or " at " ? ) Earth's surface and quite easy to be " light -excited " .
The best available choice for the plants ( At planet Earth ,at least ...).

But ,check the Magnesium's "emission" spectrum ,as an element .


http://en.wikipedia.org/wiki/Emission_spectrum
http://student.fizika.org/~nnctc/spectra/Mg_1024.htm
http://www.umop.net/spctelem.htm

Magnesium reflects / emits green photons when excited .
Plants ,simply,could not "find" a better option ,than Mg.
Still,they have evolved other photosynthetic mechanisms / substances./ accessory PS pigments ,
in order to "compensate" for that "weakness" of Mg .
Let alone ,that "green window " or the "shade avoidance ",
"mechanisms" that turn that "weakness" of Mg ,into a "survival / thriving " aiding aspect ....

Cheers.

 

[stardustsailor]

I can see it's spot on with this sheet! I calculated that number to be 119,6265659. Pretty close I'd say. Must be some difference in constants. I used:
View attachment 3384243

No worries !
You are just being very-very precise ,brother .
Well done !

Cheers !

 

[bicit]

But ,check the Magnesium's "emission" spectrum ,as an element .
View attachment 3384255

Cheers.

For some inexplicable reason I want this as a poster.... Sorry I have nothing to add, just lurking and learning

 

[Doer]

IAC the word penetration does not apply in the macro as in penetrating the canopy.

It is a micro scale term for how far the energy of green frequency will go inside an individual leaf.

It has nothing to do with canopy penetration

 

[AquariusPanta]

No. Are trying for an argument?

Are you telling us green is not reflected? It uses all frequencies but the one used the least is the one that bounces off.
http://scienceline.ucsb.edu/getkey.php?key=3949
Why no photosynthesis takes place in blue color light, and why minimum photosynthesis takes place in green color light, and Why the rate of photosynthesis is maximum in red color light?

I'm simply trying to understand the logic of your argument.

 

[Doer]

Argument?

It's a discussion.

Green penetrates farther into a leaf but the latest science says some is reflected, some is passed but most is absorbed by the deeper structures in the first leaf it strikes.

Therefore my discussion point is that the phrase about green penetrating the canopy to benefit the lower leaves is not correct.

Green is the least capable of penetrating to the lower leaves.

 

[churchhaze]

photons are not missiles.. They do not penetrate. There is no such thing as light penetration.

The only way higher absorbance can cause more "penetration" is if you burn a hole through it, but then you're penetrating through a circle of air, not the material itself.

Here's what that would look like.

The material absorbs the photons, heats up, melts/burns away, then light can freely pass through the hole.

Unlike with ballistics, one photon does not have the ability to smash through. It's the following photons that are finally able to "penetrate" through the holes in the plastic that formed from the material getting too hot.

 

[churchhaze]

The whole point is you will not be able to get enough 660nm light without bleaching the top of the canopy. You will not be able to get 660nm light deep enough into tall plant before burning the tops.

There are many analogies that can be used to help explain this.. Think about sunblock. It causes harmful ionizing radiation to be absorbed at the surface by having a low transmittance of UV-B. It's either reflected or absorbed, preventing it from ionizing your skin.

UV-B is unlikely to cause retinal damage because of how well it's absorbed by the cornea (which causes blindness regardless). UV-A, however, is transmitted through the cornea, and refracted by the lens into the retina and can cause over-excitement of the retina (burn). UV-A "penetrates" your cornea better than UV-B, despite UV-B being significantly more harmful.

Go stand under a thick canopy in a forest and look up. Is it black/gray up there? Why does it look green? Think about that one very hard. It's because leaves are like theatrical gel filters...

(the green one)

 

[ReeferDance]

Glad I brought that up.

 

[stardustsailor]

The whole point is you will not be able to get enough 660nm light without bleaching the top of the canopy. You will not be able to get 660nm light deep enough into tall plant before burning the tops.

Exactly.
Speaking about sunlight,there are not much of these photons ,usually.
(Only under the equatorial /sub-equatorial sunlight and usually for relatively short period of time,around noon.
And then ,the leaf angle gets pretty steep .I wonder why ...)

Furthermore,these photons are easily absorbed by water droplets / water vapor of the atmospheric layers.
Some photons of these deep-red wls ( a portion) are also already absorbed by the- living- leaf tissue
(As it contains up to 75-80% water.) ,thus never reaching the PS systems.
Add to that the Phytochrome absorption also-another portion not used for PS.

**
" Water owes its intrinsic blueness to selective absorption in the red part of its visible spectrum"
" The absorption below 700 nm in wavelength contributes to the color of water. This absorption consists of the short wavelength tail of a band centered at 760 nm and two weaker bands at 660 and 605 nm."

http://www.dartmouth.edu/~etrnsfer/water.htm

Go stand under a thick canopy in a forest and look up. Is it black/gray up there? Why does it look green? Think about that one very hard. It's because leaves are like theatrical gel filters...

The human vision does some automatic "white balancing"...Although you're right ,this phenomenon can be very easily be noticed with using a digital photo camera inside a forest.The CCD or CMOS sensor does not have this "auto-white balancing " ability of the human vision( ok-ok...It 's done automatically by the camera's software ,but one can disable that feature with the push of a button) .With no auto-white balance ,a white sheet of paper photographed inside a forest ,it's just ...green ,all the way !

Having said these ...
Can I place a quiz,please ?
( I just love doing that ! )

Ok ,Here it comes ...

This is a "picture " of two types of human retina ,showing the three types
of the cones that exist at the human retina.( three types of "sensoring cells" for color vision .R-G-B )


Although some individuals have lots more of the RED -photon sensitive cones ,
than the GREEN ones ...
(As for the BLUE sensitive cones ,almost all of us have relatively few of them ...)

How come ,all of us -the human individuals - have the same -highest- sensitivity at the green photons ?

Tip:
What is inside the eyeball,between the retina and the cornea ?
Void space ?
Air ?
Or.... ?


(Difficulty level : Easy as drinking a glass of ...hmm... water ! )
LOL!


Cheers.

 

[Doer]

Glad I brought that up.

Me too.

 

[AquariusPanta]

Argument?

It's a discussion.

Green penetrates farther into a leaf but the latest science says some is reflected, some is passed but most is absorbed by the deeper structures in the first leaf it strikes.


Therefore my discussion point is that the phrase about green penetrating the canopy to benefit the lower leaves is not correct.

Green is the least capable of penetrating to the lower leaves.

A discussion can hold an argument/point (or two) from multiple parties/individuals, hence "my discussion point is that the phrase about green penetrating the canopy to benefit the lower leaves is not correct.". That is clearly an argument.

Discussions can be informative like this one when multiple thoughts about a subject, such as light absorbance, take place because discrepancies typically pop up due to misunderstandings. Thankfully for us, someone usually holds the facts needed to bring the audience into a new discussion, therefore paving a way of better understanding for all.

 

[stardustsailor]

The answer to the quiz ?

( )

 

[Doer]

And that closes the loop on another oddity of science. What color appears as most number of different shades to the human eye?

Green. And they think that is survival in the forest, based. We can see more shades of green to detect movement in the foliage.