Mirrors under plants to boost light exposure?

[Fenderbender]

Yeah with a larger plant it would be negligible as at the level of the soil it's what 80 to 150ppfd or something if the plant has a bit of height, if that gets reflected up there's not much left.
With a small plant or seedling there's some difference though as there's plenty hitting the reflector.

And "Photosynthesis occurs in any cell of the plant which contains chloroplast. And underside of the leaf does contain such cells. Rate of Photosynthesis depends upon the surrounding temperature, concentration of carbondioxide and light intensity."

 

[bluter]

photosynthesis takes place primarily in the pallisade layer of cells. it's 3rd layer in and 2nd from bottom. the bottom layer does not allow light to pass to the chloroplasts, it's where the stomata are located for gas exchange. the fourth layer is where nutrients, liquid, and gasses exchange, and contacts the vein structure to accomplish the function.

 

[Fenderbender]

If I shine a led under a leaf there is no light passing through?? I can see it shine right through, pretty sure some will be activated.

 

[JiggiLotus]

 

[cannamuffinman]

I am a bit surprised no one brought up the distance the light has to travel. Keep in mind that the artificial light we use is no where near the quality of natural light from the sun.

If we are told repeatedly that there is an optimum distance between our light source and the top of the plant then bottom lighting is not going to do much of anything if it is reflected.

Using LEDs as an example, more often than not the best distance between the light source and the top of the plant is supposed to be 15-18 inches according to manufacturers and experienced growers. Many times I have read here on this msg board that after that "Goldilocks zone" the amount and quality of light drops drastically at a geometric rate for every inch it continues to travel.

Assuming that the plant is 18 inches tall from surface of soil or grow medium to the top of the canopy the light has to travel approx 36 inches to the mirror or reflective surface if the mirror is placed at soil level. However the drop in quality is not 50% because of the doubled distance but more likely 80% plus because of that pesky geometric rate of decay in quality.

Now the light bounces off the mirror and has to travel back up to the bottom of the canopy so maybe another 12 to 15 inches. Put the mirror on the same surface that the bottom of the plant pot is sitting and that increases the amount of distance to the mirror and back.

Add in the loss of quality since the light not only has to pass through layers of glass but a lot of it also had to pass through the leaves. The leaves have the job of processing the light through photosynthesis and photosynthesis converts the light and does not give light back.

Probably be better to spend the money used for the mirrors on some extra basic fertilizers and using them according to instructions the last 4 or 5 weeks of flowering with an end result of an increase in the harvest quality and quantity. That is a maybe but the chances are better with some extra macro nutrients than with a reflecting mirror.

I am seeking the error of my ways. But the white surfaces help bring light to the underleaves and I have less slightly angled on 2 sides of the plants. Trying to maximize the light from rather smaller than optimal lights. But the mirror are now gone.

 

[cannamuffinman]

Yeah with a larger plant it would be negligible as at the level of the soil it's what 80 to 150ppfd or something if the plant has a bit of height, if that gets reflected up there's not much left.
With a small plant or seedling there's some difference though as there's plenty hitting the reflector.

And "Photosynthesis occurs in any cell of the plant which contains chloroplast. And underside of the leaf does contain such cells. Rate of Photosynthesis depends upon the surrounding temperature, concentration of carbondioxide and light intensity."

Is it helpful or reckonommended to increase Co2 in the grow room? I dont know how that would b accomplish but it makes theoretical sense.

 

[Fenderbender]

Is it helpful or reckonommended to increase Co2 in the grow room? I dont know how that would b accomplish but it makes theoretical sense.

I'm no CO2 grower but adding CO2 will increase the amount of heat & light the leaves can withstand and speed up photosynthesis.
Although I have been thinking about hanging one of those baggies.. as well I tried feeding my plant around 1000ppfd and slightly over but that gets me heat stress.

 

[bluter]

If I shine a led under a leaf there is no light passing through?? I can see it shine right through, pretty sure some will be activated.

it was covered in high school. you can't pass first yr university without it. google leaf structure if you don't believe it.

any leaf with a darker waxy upper side and a lower lighter colored lighter side are built the same and have the same ancestral heritage. even pine needles have the same systems and are much earlier on an evolutionary scale

ferns and aquatics are an exception.

the cells in the pallisade level are where the majority of chloroplasts reside.

the top waxy cell layer is rain and pest protection which is why most pests attack the underside and hate rain. it contains stomata to allow water vapour to exit. it's why leaves lift in light.

upper epidermis under the top is translucent and allows light to pass. then comes the pallisade which is responsible for photosynthesis.

after that there is a tissue layer that passes nutrients and liquid from the roots through the veins to the pallisade and exchanges gasses to the lower epidermis and stomata levels. it surrounds the veins by 2/3s or more, even curving over it on the underside.

though the tissue layer has some chloroplasts it's primarily a transit system between the veins, pallisade, and lower epidermis and stomata. very little photosynthesis takes place there in most plants. the lower epidermis is not translucent and does not bother to let light pass. aquatic plants are an exception.

pass light through it all you want. all the cells will allow some to pass. you're gonna cause more damage than growth if it's intense enough. at best it does nothing.

ask any botanist.

 

[cannamuffinman]

I'm no CO2 grower but adding CO2 will increase the amount of heat & light the leaves can withstand and speed up photosynthesis.
Although I have been thinking about hanging one of those baggies.. as well I tried feeding my plant around 1000ppfd and slightly over but that gets me heat stress.

I have heard of growers using dry ice in their rooms but i don't know if there is a noticeable benefit. Some people try everything just in case. So they dont.know what works and what doesn't. I believe in keeping things as simple as possible. Cannabis likes being a weed I believe. Too much fussing is counter productive. If something will greatly.increase my yield, I will try it. But.....
Nerd run the cannabis industry. Always thought it would be hippies/ geniuses like my people.

 

[Fenderbender]

it was covered in high school. you can't pass first yr university without it. google leaf structure if you don't believe it.

any leaf with a darker waxy upper side and a lower lighter colored lighter side are built the same and have the same ancestral heritage. even pine needles have the same systems and are much earlier on an evolutionary scale

ferns and aquatics are an exception.

the cells in the pallisade level are where the majority of chloroplasts reside.

the top waxy cell layer is rain and pest protection which is why most pests attack the underside and hate rain. it contains stomata to allow water vapour to exit. it's why leaves lift in light.

upper epidermis under the top is translucent and allows light to pass. then comes the pallisade which is responsible for photosynthesis.

after that there is a tissue layer that passes nutrients and liquid from the roots through the veins to the pallisade and exchanges gasses to the lower epidermis and stomata levels. it surrounds the veins by 2/3s or more, even curving over it on the underside.

though the tissue layer has some chloroplasts it's primarily a transit system between the veins, pallisade, and lower epidermis and stomata. very little photosynthesis takes place there in most plants. the lower epidermis is not translucent and does not bother to let light pass. aquatic plants are an exception.

pass light through it all you want. all the cells will allow some to pass. you're gonna cause more damage than growth if it's intense enough. at best it does nothing.

ask any botanist.

I can't find a single page that says no though.
I did find spectogram of the absorption profile of a high nitrogen cannabis leaf.
Top one is adaxial top side

And abaxis

The top layer is just more effective.
I find that green stems can also play the photosynth.

So yeah I remain skeptical to the claim that light shining through the bottom will not activate a plant to some degree.
Now could it damage the plant if we provide high intensity from the bottom up? yeah probably easier than the topside as to the structure of the plant, as per diagram you posted they are not built up symmetrically.
But I also don't advocate for that, I just put a bit of mylar around the plant when they are small.

And okay I will, next time I'm at the Royal Botanical Gardens I'm gonna find me and pester a botanist with the question

 

[Fenderbender]

I have heard of growers using dry ice in their rooms but i don't know if there is a noticeable benefit. Some people try everything just in case. So they dont.know what works and what doesn't. I believe in keeping things as simple as possible. Cannabis likes being a weed I believe. Too much fussing is counter productive. If something will greatly.increase my yield, I will try it. But.....
Nerd run the cannabis industry. Always thought it would be hippies/ geniuses like my people.

If you wanna keep things simple well you just need enough light, good watering & nutrient practice, and know how the plants shapes so you can manicure it to produce nice buds. And first try to get the buds as big as you can with this. Should provide most with enough weed.

 

[SmokingWings]

I find that green stems can also play the photosynth.

Everywhere on the plant where there is green tissue showing is capable of photosynthesis to some degree. The area will have chlorophyll which is what gives it the green color. The same area will have the chloroplasts. Thing is will there be enough in all the green branches/stems and the petiole of the leaf; probably not enough to keep the plant healthy.

The artificial light quality, whether LED or MH or any of the others, is diluted by the distance to the reflective surface and then back to the bottom of the leaf. Then the underside of the leaf has fewer chloroplasts. The chance that any photons will penetrate the under surface and strike a chloroplast is minimal at best. Is it worth the time and energy to put a reflective surface under the plant?

In the case of the Cannabis plant the way I see it all those bracts and sugar leaves are more important. They are the leaf structures that are exposed to the most light and they are green and seem to be very capable of photosynthesis. Following the ideas behind the chlorophyll and chloroplasts the structure of the chlorophyll involves a molecule with 4 Nitrogen atoms around a single Magnesium atom. If there is not enough N the whole thing ceases to exist even with the atom of Mg and the Oxygen atoms available. One of the reasons why the plants start to take the Nitrogen from the older and often the largest leaves to move it towards the flowers.

 

[SmokingWings]

Nerd run the cannabis industry. Always thought it would be hippies/ geniuses like my people.

All them there 'nerds' are usually the hippies that became scientists, botanists and specialists that went from gardening being a hobby to being a specialty that pays their bills.

 

[Papa OG]

I use diamond plate, it's cheap doesn't need electricity. Scatters the light really well. If the canopy is too thick. I can stand it up and lean it against the tent to still hit the whole lower canopy. The shi polishes really well. Blinding.

 

[JiggiLotus]

it was covered in high school. you can't pass first yr university without it. google leaf structure if you don't believe it.

any leaf with a darker waxy upper side and a lower lighter colored lighter side are built the same and have the same ancestral heritage. even pine needles have the same systems and are much earlier on an evolutionary scale

ferns and aquatics are an exception.

the cells in the pallisade level are where the majority of chloroplasts reside.

the top waxy cell layer is rain and pest protection which is why most pests attack the underside and hate rain. it contains stomata to allow water vapour to exit. it's why leaves lift in light.

upper epidermis under the top is translucent and allows light to pass. then comes the pallisade which is responsible for photosynthesis.

after that there is a tissue layer that passes nutrients and liquid from the roots through the veins to the pallisade and exchanges gasses to the lower epidermis and stomata levels. it surrounds the veins by 2/3s or more, even curving over it on the underside.

though the tissue layer has some chloroplasts it's primarily a transit system between the veins, pallisade, and lower epidermis and stomata. very little photosynthesis takes place there in most plants. the lower epidermis is not translucent and does not bother to let light pass. aquatic plants are an exception.

pass light through it all you want. all the cells will allow some to pass. you're gonna cause more damage than growth if it's intense enough. at best it does nothing.

ask any botanist.

100%
Is this why leaves have a tendency to twist away from a light that's delivering 'too much' illumination?

I have had good outcome by placing side light bars with the plurple or mostly blue spectrum alongside the walls of my grows. The plants didn't seem to like the white spectrum síde bars, they turned away from it and it wasn't nothing strong, maybe 25w. When I rigged the blue spectrum they didn't deliver the same refusal. In an outdoor grows you have the sun rising in the east and setting in the west, so each side of the plant gets seen by the sun in that period of daylight. Plants only require so much light per day. The same way we require so many calories a day to thrive. Too much we get sluggish an fat. Not enough were malnourished and weak. That's why when we set our DLI for 12 or 18 or 20, we're giving the plant exactly what they require of sunlight per day. 12/18/20 if you look at the numbers you can actually see that were just splitting the amount into longer or shorter periods but it's relatively the same amount of illumination all n all. Just give or take how long or short the period we determined for whichever growth stage.

 

[cannamuffinman]

Everywhere on the plant where there is green tissue showing is capable of photosynthesis to some degree. The area will have chlorophyll which is what gives it the green color. The same area will have the chloroplasts. Thing is will there be enough in all the green branches/stems and the petiole of the leaf; probably not enough to keep the plant healthy.

The artificial light quality, whether LED or MH or any of the others, is diluted by the distance to the reflective surface and then back to the bottom of the leaf. Then the underside of the leaf has fewer chloroplasts. The chance that any photons will penetrate the under surface and strike a chloroplast is minimal at best. Is it worth the time and energy to put a reflective surface under the plant?

In the case of the Cannabis plant the way I see it all those bracts and sugar leaves are more important. They are the leaf structures that are exposed to the most light and they are green and seem to be very capable of photosynthesis. Following the ideas behind the chlorophyll and chloroplasts the structure of the chlorophyll involves a molecule with 4 Nitrogen atoms around a single Magnesium atom. If there is not enough N the whole thing ceases to exist even with the atom of Mg and the Oxygen atoms available. One of the reasons why the plants start to take the Nitrogen from the older and often the largest leaves to move it towards the flowers.

My lighting set up is more to get light to the lower leaves that are shadowed when the lights are only from above. It seems to encourage thick and wide branches that are less " leggy" than those that grew under a single light source from above.

I never took biology or botany so I only know what is directly applicable to growing cannabis and in new that too. Trying for maximum yield in my limited space with weaker than optimal wattage. I appreciate all the knowledge being shared. Thank you

 

[Fenderbender]

Everywhere on the plant where there is green tissue showing is capable of photosynthesis to some degree. The area will have chlorophyll which is what gives it the green color. The same area will have the chloroplasts. Thing is will there be enough in all the green branches/stems and the petiole of the leaf; probably not enough to keep the plant healthy.

The artificial light quality, whether LED or MH or any of the others, is diluted by the distance to the reflective surface and then back to the bottom of the leaf. Then the underside of the leaf has fewer chloroplasts. The chance that any photons will penetrate the under surface and strike a chloroplast is minimal at best. Is it worth the time and energy to put a reflective surface under the plant?

In the case of the Cannabis plant the way I see it all those bracts and sugar leaves are more important. They are the leaf structures that are exposed to the most light and they are green and seem to be very capable of photosynthesis. Following the ideas behind the chlorophyll and chloroplasts the structure of the chlorophyll involves a molecule with 4 Nitrogen atoms around a single Magnesium atom. If there is not enough N the whole thing ceases to exist even with the atom of Mg and the Oxygen atoms available. One of the reasons why the plants start to take the Nitrogen from the older and often the largest leaves to move it towards the flowers.

I keep looking, I just read a whole thing on Paspalum Dilatatum, but that's a C4 plant where abaxial side showed even higher CO2 absorption rates when lit on that surface.

And here this is from C3 rose.
Leaf optical properties : Rose leaves from different positions in the canopy profile showed similar optical properties in the visible spectrum. As example, Fig. 2 shows typical spectra of light transmission, reflection and absorption obtained in the middle leaves of the upright shoot (US-ML). Rose leaves lighted from the adaxial side showed low values of transmission and reflection of violet(400–455 nm) and blue (455–500 nm) light, slightly higher levels in the green region (500–580 nm), followed by a decrease in the red light (620–700 nm) and a drastic increase in the far red (from 700 nm). As a consequence, absorption was high from 400 to 500 nm and around 670–690nm, but showed a depression from 500 to 650 nm and a large drop from 700 nm (Fig. 2). Optical properties of abaxial side of leaves followed similar pattern as those of adaxial leaf side. However, light reflection and to a small extent also light transmission were higher for abaxial leaf side compared with adaxial, with consequent lower values in light absorption (Fig. 2).Averaged over the whole visible spectrum (400–700 nm)and leaf layers, rose leaves lighted from the adaxial side transmitted 4.5%, reflected 5.8% and absorbed 89.7% of the incident light (Table 1). Lighting from the abaxial side increased the average value of transmission to 5.60% and of reflection to 11.34%, with a consequent decrease of absorption to 83.06% (Table 1). Within the PAR range, green light had lowest absorption in both adaxial- and abaxial-lighted leaves, in all the leaf positions, because of increase in both light reflection and transmission (Table 1). Differences between the leaf sides were stronger in reflection than in transmission.

So is would an absorption rate of 83% not be photosynthetic?

and also penetrating green light is refracted back and forth within the leaf tissue, encountering the chloroplasts repeatedly and gradually being absorbed. This phenomenon is especially noticeable in the spongy tissue in the bottom part of the leaf, which is composed of amorphous cells.
So light absorbed from the bottom would bounce around as well and activate chloroplasts is what I'm thinking.

 

[bluter]

and also penetrating green light is refracted back and forth within the leaf tissue, encountering the chloroplasts repeatedly and gradually being absorbed. This phenomenon is especially noticeable in the spongy tissue in the bottom part of the leaf, which is composed of amorphous cells.
So light absorbed from the bottom would bounce around as well and activate chloroplasts is what I'm thinking.

when a plant exhibits light aversion due to over exposure it twists the backside of the leaf toward the light source.
it's the common sign of light aversion in every cannabis problem chart.

 

[Fenderbender]

when a plant exhibits light aversion due to over exposure it twists the backside of the leaf toward the light source.
it's the common sign of light aversion in every cannabis problem chart.

Presenting the side that's a bit more reflecting and less absorbing, seems like a good strategy.
Although that would make the underside more resistant against intense lighting?

 

[bluter]

Presenting the side that's a bit more reflecting and less absorbing, seems like a good strategy.
Although that would make the underside more resistant against intense lighting?

yes. it doesn't have the translucent epidermis layer. it is opaquer. it is meant as a protection on purpose.

topside the translucent layer is what allows the light to reach the chloroplasts. it also filters for spectrum so only the useful part is hitting the photosynthesis cells. hence the deeper green exhibited on top, and lighter on bottom.

cannabis leaves aren't particularly complex.