Please explain the phrase "Penetration" in reference to lights.

[Tater]

Well in the example you stated above with a solid wall of green their would be no light penetration. Light penetration to me as I understand it would mean the amount of light to pass through the canopy. So in the case above there would be none. I understand what you are saying and I do agree with you that the results would most likely be so little as to not be worth it at all. I've seen canopy's like that and beneath the canopy the plant is totally barren because of the lack of light. Its cool and in this set up pointless to have an extra lighting.

If that dosen't make sense its not your fault its mine I'm all messed up on painkillers. Found out I got gout hurts like a mother.

PS: Stoney I got lots of respect for you and religiously read your posts man. None of the above was intended with any disrespect, although I do know my style can come across as stinging sometimes. Its really meant in jest when it does. Here's to getting high and learn how to do that more effeciently

 

[Dub_j]

I don't think you sound "dorky" at all. You sound pretty well educated to me. You're well spoken and articulate.

I am wondering about the exact meaning of something you've said however. If penetration describes the intensity of light after passing a barrier, then please describe that barrier very specifically. The barrier penetration is the part I don't understand in what you're saying.

In your previous post, you said something about not meaning light passing through a leaf. I would agree. The intensity of light that has passed through a mature leaf would be so diminished that it really wouldn't count for much.

You also mentioned reflection. Given that a full canopy is presented that allows no direct light to pass through it, (unless a strong enough wind is provided to actually *move* the leaves), then reflection wouldn't take place, again, unless I'm misunderstanding what you're saying.

If you could give me a very specific example of light penetration, it would help me understand.

Thanks again!

Stoney

the barrier is the canopy, and any light found beyond that barrier can be said to have penetrated, or passed through the barrier (canopy). regardless of how it gets there. It seems penetration could be described as effectively maximizing light contact on all surfaces of the plant, specifically the areas that are close the the stem.

 

[massproducer]

One thing that we all must remember is that most light passes through leaves very easily, green light is the only major light that can not be used by the plant and as such is reflected so none will pass through the leaf. The most effective light at passing through the leaf surface is far red, which causes the branch to stretch towards the light.

 

[KGB30]

Thanks for the knowledge MP members...

 

[POTUS]

One thing that we all must remember is that most light passes through leaves very easily, green light is the only major light that can not be used by the plant and as such is reflected so none will pass through the leaf. The most effective light at passing through the leaf surface is far red, which causes the branch to stretch towards the light.

I disagree with what you've said. In fact, almost all light does NOT pass through the leaf barrier of a plant. The little that does, does nothing for the plant in regards to producing usable weed.

A simple test with a light meter will prove that I'm correct. Turn your lights on over a full canopy of a 4 foot tall MJ plant that has leaf that covers the entire area.

Hold your light meter below the canopy. Write down the reading. Now, hold the meter over the canopy. You'll see that about 90%+ of the light is blocked by the canopy.

Perhaps you mean something different than it sounded like.

Please explain it more in detail.

 

[Runbyhemp]

My understanding is that the more light a plant receives the higher the rate of photosynthesis. That's what we want, right ?

"Penetration" may not do anything for the lower buds, but wouldn't light hitting lower leaves help produce healthier plants in general and bigger top buds ? I would think it makes sense to say yes.

Hold your light meter below the canopy. Write down the reading. Now, hold the meter over the canopy. You'll see that about 90%+ of the light is blocked by the canopy.

It depends on how thick the canopy is, and what light you are using. 2 large fan leaves from adjacent plants can also be considered a canopy, as long as they provide a barrier from the light above. In this situation there is still plenty of usable light below the "canopy" and it is most certainly beneficial to the plants.

You said that the plant will make the leaves it needs to receive light.
Isn't this a waste of plant resources. Shouldn't we be trying to give the existing leaves as much light as possible ?

I can't scientifically prove that penetration makes a difference but nor can anyone prove that it doesn't.

 

[Tater]

I can, tell you what I'll set up an experiment with a control and do it all grade school like so that it, like all good experiments, will be repeatable by anyone. It will have to wait till winter though. I still am of the same belief as Potus though that extra lighting to provide light below the canopy is a waste of resources.

 

[Runbyhemp]

I still am of the same belief as Potus though that extra lighting to provide light below the canopy is a waste of resources.

So the leaves below the canopy serve no purpose then ?

 

[Dub_j]

This is kinda pointless...

 

[IllusionalFate]

You said that the plant will make the leaves it needs to receive light.
Isn't this a waste of plant resources. Shouldn't we be trying to give the existing leaves as much light as possible ?

Well put.

POTUS, I would say penetration doesn't literally mean light passing through a leaf, more like the opposite -- using the available spaces to allow more light to reach the lower leaves, which is just a way of saying the light is still effective at a greater radius. Therefore the only way "penetration power" wouldn't be beneficial is if the entire canopy had no available spaces or cracks leaving everything below dark and shaded. Even a grow area with a mostly full canopy from topping/FIMing and having the correct number of plants to maximize area isn't like this.

 

[POTUS]

Well put.

POTUS, I would say penetration doesn't literally mean light passing through a leaf, more like the opposite -- using the available spaces to allow more light to reach the lower leaves, which is just a way of saying the light is still effective at a greater radius. Therefore the only way "penetration power" wouldn't be beneficial is if the entire canopy had no available spaces or cracks leaving everything below dark and shaded. Even a grow area with a mostly full canopy from topping/FIMing and having the correct number of plants to maximize area isn't like this.

What you've said is exactly correct with one exception. I grow all my plants to 5 feet tall prior to harvest. Long before harvest, the canopy is as tight as a virgin bride. There is no way a photon of light gets beyond the first 12 inches of my canopy. At that point, there is no "penetration" possible.

However, I am aware of the new fad of growing tiny plants. When the little ones are taken into flower, yes, having light hit the lower leaves benefits the plant. I've never grown that way, so that type of growing isn't something I'd consider.

If "Penetration Power" is synonymous with "Usable light at longer distance" as with a 1000 watt light versus a 400 watt light over a loose canopy, then I would agree with the term.

Using Hydro in my grow room doesn't allow for a loose canopy after the plants are about 12 inches tall. Reflected light hitting the lower areas after reflecting from the walls is the only way light would reach below my canopy.

I'm glad this thread cleared up the use of the "Better Penetration" phrase.

Thanks everyone.

 

[Aurora_Indicas_Dad]

lol,this threads still goin? i thaught we were done with this 2 days ago.theres a such word as penetration, and it CAN be used when talking about lighting. not to seem like an a hole but come on potus..give it up already

 

[100percent]

The particular spectrum of a plant can have a small effect on penetration. Light does not necessarily penetrate leaves, it travels through air. But light interferes with itself. Constructive and destructive interference depends on the wavelength (or in our case, the spectrum of wavelengths) of light.

Let's imagine light passing through air and it hits a leaf. The light that hits the leaf is absorbed (with predominantly green colors being reflected) and does not penetrate through the leaf. The light that just passes the immediate edge of the leaf interferes with other waves/photons directly next to it. Normally the waves/photons are surrounded on all sides by other waves/photons but when a leaf blocks out some light then it's not symmetric anymore. This results in a blurring of the light at the leaf-air interface. If you had one light bulb above a leaf you might notice that the shadow on the floor is either not present, dim, or not the same exact shape and resolution of the leaf. That's because of interference.

So penetration, if anything, is horizontal and not vertical (assuming your lights are above the plants). Interference causes light that normally comes down vertically to "roam" horizontally a bit. In that sense, the light penetrates and covers more surface area.

So how does this all relate? Interference is physically dependent on the spectrum of wavelengths. Now how relevant is this to lights used for growing marijuana? Well, the effect is probably small, tiny, likely negligible. I only say this because most people use more than one bulb, place them in different locations, and there are many leaves, etc etc... the cumulative effect isn't really noticeable. Even with the simple system I described above, the effect is on the order of the wavelength itself, haha, though it does propagates as the light travels down vertically.

And of course, I say interference depends on the spectrum of light but you should all be asking by how much. I'm not going to pull out my notebooks but I'll hazard a guess and say that there isn't much variability in the spectra people use. Everyone is basically within the visible range with reds and blues and in-betweens. You'd notice differential penetration if you experimented with a wider range of EM radiation. (But don't do this; it's a waste and it would probably harm your plants.)

 

[massproducer]

here is an article that I found, about the light filtering abilites of leaves.

Plant leaves filter light. Specifically, leaves allow more far red light (720–740 nm) to pass through than red light (660–680 nm), thus altering the red:far red ratio below them. By altering light quality, plants perceive canopy shading via alterations in phytochrome photoequilibria that can result in increased stem elongation and reduced branching among other responses. Although we know filtering occurs and species can respond differently to an alteration of red:far red light, no data demonstrate variation in light filtering between species. In contrast to red:far red light filtering, leaves absorb much of the photosynthetically active radiation (PAR) incident on the leaf surface, but allow some to pass through.

hxxp://www.actahort.org/books/711/711_24.htm - Reference citation

 

[massproducer]

if no light could pass through the leaf surface then anything being shaded would quickly yellow and die, because of a lack of photosynthesized tissue. If you research the far red spectrum then you would see that hardly any of this is absorbed by leaves, it is used by the stem to elongate and try and reach a higher concentration of light

I also have an experiment for everyone to try, and it is very easy. First take a nice healthy leaf, any leaf, and hold it up to either the sun or your grow lights and tell me what you see. It light could not pass through the leaf, it should look like holding up panda film, mean you see no light through the leaf, but i bet you will see a lot of difussed light through the leaf.

I now also have a challenge for everyone who blasted me...PLEASE find something that can be referenced or cited, stating that NO light can pass through a leaf surface. Leaves are Translucent, not opaque.

 

[massproducer]

The problem with this experiment is that the law of diminishing light shows us that placing the light meter and more then 1 feet away is going to cause a drastic decrease in light with or without a canopy. The light that is being "blocked" is mainly the green/yellow spectrum that the plants can not use that gets reflected back up, so they do not get too hot.

I disagree with what you've said. In fact, almost all light does NOT pass through the leaf barrier of a plant. The little that does, does nothing for the plant in regards to producing usable weed.

A simple test with a light meter will prove that I'm correct. Turn your lights on over a full canopy of a 4 foot tall MJ plant that has leaf that covers the entire area.

Hold your light meter below the canopy. Write down the reading. Now, hold the meter over the canopy. You'll see that about 90%+ of the light is blocked by the canopy.

Perhaps you mean something different than it sounded like.

Please explain it more in detail.

 

[KGB30]

if no light could pass through the leaf surface then anything being shaded would quickly yellow and die, because of a lack of photosynthesized tissue. If you research the far red spectrum then you would see that hardly any of this is absorbed by leaves, it is used by the stem to elongate and try and reach a higher concentration of light

I also have an experiment for everyone to try, and it is very easy. First take a nice healthy leaf, any leaf, and hold it up to either the sun or your grow lights and tell me what you see. It light could not pass through the leaf, it should look like holding up panda film, mean you see no light through the leaf, but i bet you will see a lot of difussed light through the leaf.

I now also have a challenge for everyone who blasted me...PLEASE find something that can be referenced or cited, stating that NO light can pass through a leaf surface. Leaves are Translucent, not opaque.

Thanks for this thread it has help me out to understanding light in how react with plants & canopy. Thank MP members

 

[POTUS]

lol,this threads still goin? i thaught we were done with this 2 days ago.theres a such word as penetration, and it CAN be used when talking about lighting. not to seem like an a hole but come on potus..give it up already

If you have nothing good to say, why bother saying anything?

Don't open the thread and don't read it if it bothers you.

 

[massproducer]

I thank you Stoney because IMHO, this is a good topic of research, I always enjoy interjecting with knowledgeable members on advanced topics such as these. IMHO, there have been many pertinient points mentioned in this thread, and it is interesting how we all deseminate the information availible or provided.

I highly respect most everyone who has contributed to this thread. I say keep the info coming as long as it is relative. I love this stuff.

Great job Stoney...You will always be stoney to me...LOL

 

[POTUS]

The problem with this experiment is that the law of diminishing light shows us that placing the light meter and more then 1 feet away is going to cause a drastic decrease in light with or without a canopy. The light that is being "blocked" is mainly the green/yellow spectrum that the plants can not use that gets reflected back up, so they do not get too hot.

Excellent discussion massproducer! I've enjoyed it.

Of course, the light penetration that is being referenced when "Better Penetration" is pointed out, is *usable* light for the plant.

You and I agree on the fact that little beneficial usable light is going to pass through a leaf and that light that does reflect from the leaves won't be of a sufficient amount to do much either. The only light that will have any real benefit to the plants is that which is either direct or reflected from a surface that is highly reflective.

The strength of light in this category would of course be more penetrating if a larger light is used. If this is the real meaning of "Penetration" when used as "Better Penetration" when discussing a grow, then I'm all for it.

Great talk man.

For those that did nothing but whine about this thread, next time, just don't enter threads that bother you so much. It's kind of like going into a movie you don't like and making wise cracks about it that everyone else can hear. Hey, they might like the movie. You shoulda just not went in.

Thanks for the discussion. It was fun and informative.