Light ???

churchhaze

Well-Known Member
Churchhaze, you're well known on this forum for your negativity and lack of constructive comments. Therefore I choose to ignore you. For others reading the forum, I did buy a 4 pack of 8.5w LED bulbs today and replaced the 9w CFLs I was using for rooting clones. 800 lm vs 550. It was Sylvania brand, the kind that have a round diffuser on them that looks like a normal light bulb. Even though I have them positioned horizontally they still give out plenty of light in all directions with that diffuser, which should be gentler on the clones than if it was blasting straight down at them. In a cloning situation, LED bulbs are appropriate because they actually cost no more than CFLs of similar wattage and produce more light, I got 4 for $12 something. Only problem is that it's only these small bulbs that are reasonably priced, and obviously you couldn't really put 40-60 of them in a 1 m2 space because it would just not be practical with all the wiring and sockets etc. Even the larger 24w grow bulbs would require about 20 or more.
You have a reputation for thinking that HPS lamps aren't very good for growing plants.

HPS are great for keeping food warm, but for growing plants, not so great.
:dunce:
 
Last edited:

BobCajun

Well-Known Member
You have a reputation for thinking that HPS lamps aren't very good for growing plants.



:dunce:
Oh I do not. I hardly ever mention HPS at all. Just doesn't come up that often. I'm just going by experience. I find they burn plants up too much and produce too much heat in general. Just too problematic to deal with compared to LED and CFL.
 

Doogan

Well-Known Member
After reading the "midday depression" portion of the first post I felt it was necessary for me to "intervene".

Exceeding a plants "light saturation" has little to no negative effect on photosynthesis. It is the heat associated with light that causes "midday depression". This is fact and explored here-

"In a growth chamber that simulated field growth conditions, photosynthesis declined dramatically when the temperature was higher than 32 °C. Photosynthesis was also reduced when photosynthetically active radiation (PAR) exceeded the saturating point of Oncidium. Gower Ramsey, which is about 250 μmol·m-2·s-1. However, the reduction was slight when PAR was under 500 μmol·m-2·s-1. Daily photosynthetic patterns were changed when Oncidium Gower Ramsey was grown under different environments. By regression, we found that MD was not directly associated with PAR within the range of 0–400 μmol·m-2·s-1. By contrast, photosynthesis was significantly reduced when temperature was higher than 32 °C. This explains the observation of greater photosynthetic reduction and earlier occurrence of MD when OncidiumGower Ramsey was grown in rain-shelter rather than in phytotron and growth chamber, since temperature in the rain-shelter was not controlled, while the others were controlled at 25 °C. When Oncidium Gower Ramsey was moved from 35 °C to 25 °C, the photosynthetic depression was relieved."

Link- http://hortsci.ashspublications.org/content/41/4/1056.4.short



This happens due to stomatal constriction as the plant attempts to hold on to as much water as possible (it stops "sweating"). This also results in cellular depletion of CO2. Closed stomata, low internal CO2 volume, "droop", the plant halts photosynthesis, it is essentially "sleeping". This is also fact, explored here-


"Light - exerts strong control. In general: light = open; dark = closed. ... (c) reduces internal CO2 levels which stimulates opening (see below)."

"Carbon dioxide - intracellular level is most critical. This is an important regulatory control.
lo CO2 (i.e., during the day, used by photosynthesis) = open (stoma)
hi CO2 (i.e., at night, produced during respiration) = closed (stoma)"

"Temperature - increased temperatures usually increase stomatal action, presumably to open them for evaporative cooling. If the temperature becomes too high the stomata close due to water stress and increased CO2 that results from respiration."

Link- http://employees.csbsju.edu/ssaupe/biol116/Botany/plant_gas_exchange.htm


By subjecting your plants to a 30 minute "lights out" period in the middle of your 12 hours "day" period, you are effectively imposing an "artificial" midday depression upon your plants, the very thing you are attempting to avoid. Also, by running your temps above 77F/25C (+ or - 2F depending on plant/strain) you are recreating the catalyst of midday depression, excessive heat. Only, this is not just at "midday", it is for the entirety of the "day" as this is the constant throughout your "lights on" period. So, not only are you forcing "midday depression" for 30 minutes, but you are intentionally subjecting them to "all day depression" with high temps.



Another negative effect of the high temps is that it lowers the plants light saturation threshold. High temps lower the plants ability to use "light" and perform photosynthesis. This is why we want to lower temps, maintain good air circulation over the leaves, and increase the availability of CO2. This increases the plants light saturation threshold, boosts it's metabolism, which means increased rate of photosynthesis.

CO2 also assists in maintaining temps at the canopy level (hopefully you have you meter mounted just above). Little known fact, CO2 is less heat conductive than O2. This means that the heat from your lights (which wants to rise anyways) is "circulated" easier/faster through the low CO2 air above the canopy, the heat has more difficulty "penetrating" the high CO2 air at and below the canopy.





Not attempting to knock anyone's methods, I just don't want any newbies to be steered in the wrong direction. We are all always learning, anything that benefits our mind and grow should be appreciated. I believe that even in "researching", many misinterpret, or simply do not understand, the research findings as they are presented.
Could you instead lower the power during "midday depression" instead lights off? Or evan shut some off for 30 and leave some on....?
 

BobCajun

Well-Known Member
I tried that in one veg room . A couple strains started flowering in veg. It was 5 out of 20 plants. I went back to 18/6.
Weird, but interesting. Mine reveged on it from cuttings taken at 6 weeks flower. Completely vegetative right now. Was it all one strain that flowered?
 
Last edited:

hyroot

Well-Known Member
Weird, but interesting. Mine reveged on it from cuttings taken at 6 weeks flower. Completely vegetative right now. Was it all one strain that flowered?
It was blue balls, nightmare cookies, and quantum kush. They started flowering then after pistils started forming. They went through the reveg stage. Then I immediately switched back to 18/6.
 

BobCajun

Well-Known Member
It was blue balls, nightmare cookies, and quantum kush. They started flowering then after pistils started forming. They went through the reveg stage. Then I immediately switched back to 18/6.
Sure it wasn't just normal single flowers at nodes? Hard to believe a plant could flower on 2 hours of darkness, in fact impossible to believe. Anyway, probably doesn't make much difference. My plants look healthy though and grow fast. I don't think they like being in the dark for long periods. I think they're growing better than 18/6 but it's just visually.
 

hyroot

Well-Known Member
Sure it wasn't just normal single flowers at nodes? Hard to believe a plant could flower on 2 hours of darkness, in fact impossible to believe. Anyway, probably doesn't make much difference. My plants look healthy though and grow fast. I don't think they like being in the dark for long periods. I think they're growing better than 18/6 but it's just visually.
They were forming buds at each top.

it takes 2 hours of darkness to send a plant into its phytochrome state. With IR ot takes a few min.

So when the lights came back on. The plants might have thought it was new day.

Like all other training methods and longer day manipulation , it's strain dependent.
 

Odin*

Well-Known Member
Could you instead lower the power during "midday depression" instead lights off? Or evan shut some off for 30 and leave some on....?


No. You do not want to alter the light cycle to impose an artificial midday depression on the plants. I was referring to the original post, which suggests recreating the midday depression (through darkness, not heat, but that still generates the same result) and applying excessive heat are beneficial. This is not true, both bring photosynthesis to a halt. One of the studies (links) I posted concluded that it is the temperature, not "light saturation" that causes midday depression.

Cool temps, CO2 supplementation, ample water, lots of light, that's what you want.


I wanted to touch on major changes in the light cycle during bloom. Some strains can handle it, if other stressors aren't there to push it beyond it's stress limit. Others cannot, or have already been subjected to enough stress that major changes in the lighting will push it to herm. I know this not only from reading (more below), but first hand experience. I've changed the light cycle in mid bloom before without issue, so when it was becoming exceptionally hot (several years back), I didn't think twice about shutting the lights off for two days, to "reset" and switch it over to "on" at night (it had been "on" during the day). I had neglected to consider my "Mystery". She's high maintenance, isn't afraid to go bananas over the slightest "imperfection" in the environment. The two days off and change in the cycle made her flip her cookie, threw bananas at everybody, and left me with a crap ton of seeds (I kept about 1k).
As I mentioned above, I looked into it to see if I could find anything directly linking the "lights out" to the banana fest. Sure enough, I read (don't remember if it was an excerpt from a book, or the breeder chiming in on one of the Forums) that a well known and respected breeder shut the lights off mid bloom to identify any "sensitive" plants (hermie tendencies) so that they could be eliminated from breeding stock.
 

ttystikk

Well-Known Member
I suspect that midday depression occurs because of conditions being hostile to growth, like excessive temperatures and RH. If these are kept in their ideal range, the plant has no need to slow down.
 

RM3

Well-Known Member
No. You do not want to alter the light cycle to impose an artificial midday depression on the plants. I was referring to the original post, which suggests recreating the midday depression (through darkness, not heat, but that still generates the same result) and applying excessive heat are beneficial. This is not true, both bring photosynthesis to a halt. One of the studies (links) I posted concluded that it is the temperature, not "light saturation" that causes midday depression.
Some how you missed that I run a hot canopy, The reason I wrote the post was because lots of folks wanted to know how I get the results I get usin T5's, you may be right bout it shuttin down things but it works a charm, I've been doin it for years
 

Odin*

Well-Known Member
@RM3 I didn't miss that bit and I don't doubt that you've dialed in your setup to run at, or close to, it's best. With higher temps, the plants will sweat more, this forces them to drink more, which assists in keeping the roots healthier. However, the constant sweating/loss of water is what prevents the buds from developing the bulbous calyxes. The "sweating"/heat also decreases terpene development. This might explain why your garden doesn't "stink". If you cooled your room via AC, the AC would pull water from the room (condenser), maintaining a similar level of soil moisture, but your plant would not be drawing up that water and "sweating". That alone would completely change your "feed" and watering schedule.



To illustrate the drastic difference that temperature makes, here is my GSC, grown in higher temps. Notice the lack of bulbous calyxes, the amount of leaves (in bud), the hairs, the color (which is determined by terpenes, as is scent and flavors).





Here is that exact same strain (my GSC, all from a single original clone), only grown in cooler temps. No other change was made, same medium, same feed schedule, same room. Look at the change in bud structure. Bulbous calyxes, very low leaf count, very few hairs, all purple (increased terpenes). I will also say that the nose is far stronger/complex, flavors are better as well as more complex, and the smoke is more potent, the high more complex and longer in duration. This is the healthier/happier plant and sets the bar that every run with this strain will be measured against. As long as I can maintain those temps, she will come out identical each time, everything else is in perfect order.



Here is some glue from that same run.







You can grow herb in higher temps, I've churned out fire from 88F, but that doesn't mean that it was grown in optimal conditions, or was as good as it could have been. Again, cooler temps, CO2 supplementation, roots, watering, nutrients, etc. at "perfect" levels allow for a greater light saturation threshold, which increases metabolism, resulting in boosted rates of photosynthesis. Higher temps lower the light saturation threshold and slows/stops the metabolism, which decreases/stops photosynthesis.
 

whitebb2727

Well-Known Member
I suspect that midday depression occurs because of conditions being hostile to growth, like excessive temperatures and RH. If these are kept in their ideal range, the plant has no need to slow down.
I can tell you it has been right around 100 here this summer. Heat indexes of 115. High humidity.

We went a long spell with no rain and even the big hardwoods were starting to yellow.

We finally got a couple weeks of rain.

Aot of plants in the garden and around the house just curl up mid day.

I've got a few flowering and trucking right along.
 
Last edited:

hyroot

Well-Known Member
I can tell you IG has been right around 100 here this summer. Heat indexes of 115. High humidity.

We went a long spell with no rain and even the big hardwoods were starting to yellow.

We finally got a couple weeks of rain.

Aot of plants in the garden and around the house just curl up mid day.

I've got a few flowering and trucking right along.
My outdoor was doing the same. Yellowing and curling and twisting leaves. It's been 105-115 everyday and 85 -105 at night. Even with shade cloth. Since I started watering with activated labs (lactobacillus serum) they have been perky during the day. Which never happens this time of year
 

whitebb2727

Well-Known Member
My outdoor was doing the same. Yellowing and curling and twisting leaves. It's been 105-115 everyday and 85 -105 at night. Even with shade cloth. Since I started watering with activated labs (lactobacillus serum) they have been perky during the day. Which never happens this time of year
I got a sample from rxgreensolutions. It has different bacteria in it. It has made a difference.

Its called root.


https://www.rxgreensolutions.com/root.html
 

ttystikk

Well-Known Member
@RM3 I didn't miss that bit and I don't doubt that you've dialed in your setup to run at, or close to, it's best. With higher temps, the plants will sweat more, this forces them to drink more, which assists in keeping the roots healthier. However, the constant sweating/loss of water is what prevents the buds from developing the bulbous calyxes. The "sweating"/heat also decreases terpene development. This might explain why your garden doesn't "stink". If you cooled your room via AC, the AC would pull water from the room (condenser), maintaining a similar level of soil moisture, but your plant would not be drawing up that water and "sweating". That alone would completely change your "feed" and watering schedule.



To illustrate the drastic difference that temperature makes, here is my GSC, grown in higher temps. Notice the lack of bulbous calyxes, the amount of leaves (in bud), the hairs, the color (which is determined by terpenes, as is scent and flavors).





Here is that exact same strain (my GSC, all from a single original clone), only grown in cooler temps. No other change was made, same medium, same feed schedule, same room. Look at the change in bud structure. Bulbous calyxes, very low leaf count, very few hairs, all purple (increased terpenes). I will also say that the nose is far stronger/complex, flavors are better as well as more complex, and the smoke is more potent, the high more complex and longer in duration. This is the healthier/happier plant and sets the bar that every run with this strain will be measured against. As long as I can maintain those temps, she will come out identical each time, everything else is in perfect order.



Here is some glue from that same run.







You can grow herb in higher temps, I've churned out fire from 88F, but that doesn't mean that it was grown in optimal conditions, or was as good as it could have been. Again, cooler temps, CO2 supplementation, roots, watering, nutrients, etc. at "perfect" levels allow for a greater light saturation threshold, which increases metabolism, resulting in boosted rates of photosynthesis. Higher temps lower the light saturation threshold and slows/stops the metabolism, which decreases/stops photosynthesis.
@RM3 runs his RH quite low, so this doesn't become a problem in his application.

He's after resin maximization, not yield. It's a different mindset.
 

churchhaze

Well-Known Member
Some how you missed that I run a hot canopy
by running your temps above 77F/25C (+ or - 2F depending on plant/strain) you are recreating the catalyst of midday depression, excessive heat. Only, this is not just at "midday", it is for the entirety of the "day" as this is the constant throughout your "lights on" period. So, not only are you forcing "midday depression" for 30 minutes, but you are intentionally subjecting them to "all day depression" with high temps. Another negative effect of the high temps is that it lowers the plants light saturation threshold. High temps lower the plants ability to use "light" and perform photosynthesis. This is why we want to lower temps, maintain good air circulation over the leaves, and increase the availability of CO2. This increases the plants light saturation threshold, boosts it's metabolism, which means increased rate of photosynthesis.
:wall:
 
Top