Avoid Misconceptions When Teaching About Plants

spurr · Dec 8, 2010

Hey all,

Here are two good articles by David R. Hershey that debunk many wrong ideas in plant science, I especially like the part about green light, etc. I have a few studies showing that green light, under bright (high irradiance) white light (ex. HID) can drive rate of photosynthesis more than blue and red light.

The claims that green light isn't useful is total BS, and based upon flawed 'chlorophyll A/B absorption spectrum' curve passed around the cannabis world for many years (found via. a leaf extract inside a "spectrophotometer"; see this example). That is one major reason I dislike most LED arrays: they lack sufficient green light.

The 'action spectrum of photosynthesis' gives a much better representation of quantum yield from blue, green and red range light than does the 'chlorophyll a/b absorption spectrum'. Albeit the quantum yield of green light from high irradiance white light is undervalued in Kieth McCree's 'action spectrum of photosynthesis' (which is why Keith McCree's work, re: Quantum Flux Density and Quantum Yield Curve, are a bit flawed).

"Avoid Misconceptions When Teaching About Plants"
David R. Hershey
http://www.actionbioscience.org/education/hershey.html

"More Misconceptions to Avoid When Teaching about Plants"
David R. Hershey
http://www.actionbioscience.org/education/hershey3.html

budlover123 · Jan 9, 2011

I was thinking that LEDs might be cool as a low power supplement to HPS to balance out the light spectrum a bit, like a bunch of royal blues and a couple white to balance it out, maybe green would be a better choice, that would make a nice cyan color. I've seen 1350 mW of royal blue leds change the color of a 400 watt HPS pretty noticeably, I'd like to test some green leds. Those direct color LEDs are something

edit: its noticeable to the naked eye, but a camera with standard white balance doesn't show a big difference

Azeotrope · Jan 10, 2011

If you only knew how many times I have heard the "green light is worhtless to plants" myth while discussing the CMH bulbs I like......... Just drives me crazy! Yes they have a large spike in that area of the spectrum and I like it.

foomar · Jan 10, 2011

Good link spurr , these two examples could save a lot of arguments , well worth reading in full .

A widespread misconception states that leaves reflect all green light and do not use green light in photosynthesis. Leaves often absorb more than 50% of the green light and use it efficiently in photosynthesis.The origin of this misconception is probably the chlorophyll absorption spectrum in textbooks. The chlorophyll absorption spectrum is a graph of light absorption versus light color. It shows that chlorophyll absorbs much red and blue light but little green light. However, accessory pigments absorb green light and pass that energy on to chlorophyll.

Capillarity is not a factor in upward water movement in stems. Capillarity occurs in tubes of small diameter that are initially empty. Water spontaneously moves up such tubes. Functional xylem comprises small diameter tubes that are not empty to begin with.

GreenintheThumb · Jan 11, 2011

So do you think that green light can upset the night cycle?

trichrider · Jan 11, 2011

that was inevetible...

mean mr.mustard · Jan 11, 2011

guest456mpy · Jan 11, 2011

Mind your own advise, please !

Mind your own advise, please !

Math-durbators will rise and follow him! The rest will need actual proof.

Here's a tent full of plants grown entirely with 300 watts of LEDs at day 42 of 12/12. They stand 36" tall and the central colas are 18" by 3 1/2 inches. In fact the only thing hold back their height was the top of the tent. It's nice to read and try to understand how things will affect growth and maturation, but in the end experimentation will prove theories right or wrong.

If you like HID's fine! But don't try and and BS others into following you in order to stroke your ego, it's just not right.

Unclepeter · Jan 13, 2011

GreenintheThumb said:
So do you think that green light can upset the night cycle?

if on all night, but green by itself is bad IMO, when used alongside red/blue and purple as each pigment absorbs differently to each other its beneficial, chlorophyll a likes red/yellow to green, b likes red,green and blue c and d are green and bacteriochlorophylls a-d likes pale blue to purple in this case its fine. but both c and d are more for algae production. higher plants typically like red/blue to green.

mean mr.mustard · Jan 13, 2011

So where's all this red light useful?

What about phytochrome?

Unclepeter · Jan 13, 2011

mean mr.mustard said:
So where's all this red light useful?

What about phytochrome?

chlor a I think from memory is a red fan (like myself

) it is also in effect a signal for flowering thru the use of the red triggering phytochrome pigments, some also say with cholr a it makes use of red, some specifically use green and blue for veg!.

ps. that man in your avi touched me as a kid (still not the same haha)

mean mr.mustard · Jan 13, 2011

If you can find chlorophyll that isn't green I'd agree that it uses green light.

Until you do I will smoke some joints.

superpedro · Jan 13, 2011

spurr said:
Hey all,

Here are two good articles by David R. Hershey that debunk many wrong ideas in plant science, I especially like the part about green light, etc. I have a few studies showing that green light, under bright (high irradiance) white light (ex. HID) can drive rate of photosynthesis more than blue and red light.

The claims that green light isn't useful is total BS, and based upon flawed 'chlorophyll A/B absorption spectrum' curve passed around the cannabis world for many years (found via. a leaf extract inside a "spectrophotometer"; see this example). That is one major reason I dislike most LED arrays: they lack sufficient green light.

The 'action spectrum of photosynthesis' gives a much better representation of quantum yield from blue, green and red range light than does the 'chlorophyll a/b absorption spectrum'. Albeit the quantum yield of green light from high irradiance white light is undervalued in Kieth McCree's 'action spectrum of photosynthesis' (which is why Keith McCree's work, re: Quantum Flux Density and Quantum Yield Curve, are a bit flawed).

"Avoid Misconceptions When Teaching About Plants"
David R. Hershey
http://www.actionbioscience.org/education/hershey.html

"More Misconceptions to Avoid When Teaching about Plants"
David R. Hershey
http://www.actionbioscience.org/education/hershey3.html

Around 50% of green light is reflected. The rest is used - got it

But are you saying it drives photosynthesis more than twice as good as blue and red, and should be used in a LED array regardless of the 50% loss by reflection?

mean mr.mustard · Jan 13, 2011

Green light is our savior!!

:jump:

Don't buy into misconceptions when learning about plants... :tiphat:

I'm waiting for someone to point out that green wavelength is the only reason the sun grows bigger plants than HIDs.

:jerkit:

Unclepeter · Jan 13, 2011

mean mr.mustard said:
If you can find chlorophyll that isn't green I'd agree that it uses green light.

Until you do I will smoke some joints.

and when the plant changes to red or yellow leaves what has it done with the green? same applies in the cold!

and Mr mustard you can grow bigger under lights than the sun.

they used to think the red light was the source for algae as it was thought the spectrum to penetrate but its been found to be blue I think.

mean mr.mustard · Jan 13, 2011

When no longer necessary the plant cannabilizes the chlorophyll leaving anthocyanins to come out visably on the leaf surface.

I can grow bigger plants under the sun than indoors under lights.

Green light isn't worth a fart in a jar if you're a plant... that's why they're green.

Unclepeter · Jan 13, 2011

mean mr.mustard said:
When no longer necessary the plant cannabilizes the chlorophyll leaving anthocyanins to come out visably on the leaf surface.

I can grow bigger plants under the sun than indoors under lights.

Green light isn't worth a fart in a jar if you're a plant... that's why they're green.

first bit doesn't explain red/purp in colder climates.

Green light isn't worth a fart in a jar if you're a plant... that's why they're green

that there is bullshit

Kopite

VerdantGreen · Jan 13, 2011

yep, plants use green light just fine- why wouldnt they when it's such a large part of the sunlight spectrum.

superpedro · Jan 13, 2011

VerdantGreen said:
yep, plants use green light just fine- why wouldnt they when it's such a large part of the sunlight spectrum.

Yes they can use green, they do under the sun. But isn't artificial lighting not about what they use best?
If 50% is reflected I can't see how it should efficient enough - more than twice as efficient - I doubt it..

mean mr.mustard · Jan 13, 2011

I'm eagerly awaiting an explanation as to why plants without green light do just fine.

I was happy to stay out of the Breeder's Forum when I realized what was to be found for "knowledge".

Just say the word and I'll stay out of this one too.

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