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temperature VS light

Pfeffer

Pfeffer

Hi all,

I'm starting some chinenses as we north western Europeans have a lot shorter growing seasons than a lot of you. My current set up for seedlings is; two 24" 6500k TLs over an heated 50w propagator.

I'm currently dosing them with a 19/5 lighting schedule in combo with a steady 28*c (82.4 Fahrenheit). The 19/5 worked better than 18/6 for me in the past, but that was without heat source.

Do you guys have tips to tweak my grow?

I read a lot on the Subject. Some people do 24/0 or 16/8, but there's no info on the actual effects. Also some people Cool the seedlings down to 21*c / 71 F during the artificial night. Is this just energy saving or does it have a use?

An other thing that I'm wondering is if I can start with co2 fertilizing. (i.e. by burning a candle or adding a minimal dose of dry ice to the room, my current co2 level is approx 250-310 ppm).

I'm welcoming all advice as I'm having a lot of issues sorting crap from truth on the mighty interwebz. There are just too many theories about photosynthesis.

My goal is to get plants with as many internodes as possible as I'm a large fan of topping/pruning.
 
Your title isn't really accurate - it's not temperature VS light, but temperature AND light. Temperature is easy - don't let them cool down below 50F and don't let them heat up above 89F for ideal conditions. Light is where the most disagreement comes in - some say 24/0 while others say a period of rest. I am in the group that believes a period of rest is required by every living thing. Those that say 24/0 believe the growth is greater. IMO it probably averages out over time - at some point the plants will get too stressed and slow down at 24/0. And note I don't necessarily mean over a handful of days, but particularly if you plan on keeping plants going for more than one season.
 
Think about yourself first - what happens to you if you stay up all night and all day for days on end? You finally crap out at some point. And what happens physiologically as well as psychologically with you when you sleep? Your brain sorts out all the info bombardment it received throughout the day. Your immune system strengthens and your body heals from any tearing down you did during the day (exercise, for example, has a certain tearing-down effect on the muscles and sleep repairs this.) While plants are not identical, there are similarities, which I'll illustrate with another point. Anyone with a very young child has likely experienced being able to easily put shoes on that child one day, then BOOM the next day the shoes wouldn't go on at all. All of us who ensure our plants get rest at night can report the same - one day you go out and see the plants one size, the next day you go outside and the plants seem to have almost  doubled in size. This seems to indicate that, at least during the growth phases, something good is happening with both plants and animals during periods of rest. 
 
At the end of the day you have to decide for yourself. I always recommend doing a personal experiment to help make this decision. Take half your plants and give them light 24hrs/day and give the other half a period of rest each night. Make sure you have some of the same varieties in both groups so that variety differences aren't a factor. Note for yourself how each group does (measure how tall and wide each are, as well as how many pods each puts out, and record them over time), then decide from there. Most likely one group will out-perform the other. 
 
Everything that geeme said ^.
 
Just to comment on the night time temps point, like insects, the general growth rate of plants have a direct positive relationship to the ambient temperature (at least in the range that they do grow).
As we want faster growth with seedlings, I would safely assume it's better to keep them warm at night as well--as long as they don't dry out overnight in the heat.
(but would it make a lot of a difference? it might make your plants more leggy. I remember there was a study flipping the day/night temps, where they found you could make your pepper plants grow real stocky and sturdy)
Now when it comes to flowering and fruiting time, you're definitely going to want cooler night time temperatures as the temp variation between the diurnal/nocturnal cycles regulates flower and pollen formation.
 
As for CO2, do you have means to keep the CO2 in the room? Think it might seep out.
 
No it don't plan in sealing it, but it's a relatively heavy gas so it will go down. The idea was to just locally increase the co2 level by putting a candle or a small amount of dry ice in a container over the propagator. I think this would just have a minor effect if it has effect at all, I was just hoping someone already experimented on it. Also, levels of more than 2150 ppm are lethal to humans (not toxic, but it simply derrive you of oxygen). Therefore also in small quantities only.
 
I unfortunately don't have two growth set-ups so I can experiment between two groups. The point about the leggy plants seems to be logical as temperature influences the photosynthesis, which is at it's premium around 27*C-28*C plants but I haven't tested it yet. Therefore I was also hoping that someone already tried this before. I don't really feel like reinventing the wheel if others already tried and failed (or succeeded).
 
geeme said:
Your title isn't really accurate - it's not temperature VS light, but temperature AND light. Temperature is easy - don't let them cool down below 50F and don't let them heat up above 89F for ideal conditions. Light is where the most disagreement comes in - some say 24/0 while others say a period of rest. I am in the group that believes a period of rest is required by every living thing. Those that say 24/0 believe the growth is greater. IMO it probably averages out over time - at some point the plants will get too stressed and slow down at 24/0. And note I don't necessarily mean over a handful of days, but particularly if you plan on keeping plants going for more than one season.
 
Think about yourself first - what happens to you if you stay up all night and all day for days on end? You finally crap out at some point. And what happens physiologically as well as psychologically with you when you sleep? Your brain sorts out all the info bombardment it received throughout the day. Your immune system strengthens and your body heals from any tearing down you did during the day (exercise, for example, has a certain tearing-down effect on the muscles and sleep repairs this.) While plants are not identical, there are similarities, which I'll illustrate with another point. Anyone with a very young child has likely experienced being able to easily put shoes on that child one day, then BOOM the next day the shoes wouldn't go on at all. All of us who ensure our plants get rest at night can report the same - one day you go out and see the plants one size, the next day you go outside and the plants seem to have almost  doubled in size. This seems to indicate that, at least during the growth phases, something good is happening with both plants and animals during periods of rest. 
 
At the end of the day you have to decide for yourself. I always recommend doing a personal experiment to help make this decision. Take half your plants and give them light 24hrs/day and give the other half a period of rest each night. Make sure you have some of the same varieties in both groups so that variety differences aren't a factor. Note for yourself how each group does (measure how tall and wide each are, as well as how many pods each puts out, and record them over time), then decide from there. Most likely one group will out-perform the other. 
Click to expand...
+1 something tells me you've grown peppers before? :P The plants sleep whenever I sleep and get light whenever I wake up.
 
Here's a good example: Look at the plant in the small terra cotta pot on the lowest step in this pic:
g2_20110720.jpg

 
The info I had on that variety indicated it wouldn't get more than 18-24" tall. Now look at it just 8 days later - I had thought at the point above it likely should be repotted, and it decidedly needed repotting when I saw it on that 8th day, so did that before taking this pic (now in green pot on the ground):
g1_20110731.jpg

 
It was doing slow-and-steady growth during the week between, but it really popped overnight. The plant turned out over 3' tall - pot and plant came to my shoulder height when fully grown.
 
Changed my timer to

1. 06:00-19:59 = 28*c
2. 20:00-23:59 = 27*c
3. 00:00-05:59 = 21*c

atleast for the time being, phase 3 is in the dark.
 
I struggled to read a technical paper 2 months ago that dealt with peppers grown under 24 hours/day of light. Apparently, over a period of 5-6 weeks, the leaves start to accumulate carbohydrates, and this is bad for the plant.
I re-read this document carefully, and that's about all the information i could be certain of.

As for CO2 enrichment, i suspect a candle might do more harm than good: the partially combusted petrochemicals ("pyrolytic compounds") are likely to clog the plants' stomata (breathing pores).

I recently discussed using vermiculture bins as a CO2 source: they emit it at a very steady rate, use no flame or dangerous chemicals... and the worms (usually genus Eisenia) are themselves tolerant of low oxygen levels. Thus, if too much CO2 accumulates, they're less likely to die than most animals.
However, they do not fare well at temperatures above 80F (26C).

I hope these observations are useful. I'm not yet finished planning my solution for CO2 supplementation, and thus cannot offer you a better answer.
 
I already got advice from one of our chemists at work; bicarbonate and acid (i.e. baking soda and citric acid). He'll look up the correct ratio for me. It can be mixed as dry powders and will decompose when you add water. You only need very limited quantities.
 
I rarely agree with CO2 supplementation unless you have a way to measure and control the release. Anything over 1500ppm is harmful to the plant, and higher levels of CO2 (ideally 1200ppm) will cause havoc if your environment is not perfectly dialed in, temperature, humidity, nutrients, etc.
 
I do have professional measuring equipment (titan atlas 5) and can provide a protected enviroment (greenhouse + large propagator). But I can't find the values, but if I understand correctly you have experience with co2 fertilizing?

Will anything above average will provide a boost or will I need to stick to a certain range?

What humidity range would be good? And I figure a frequent but dilluted (i.e hydroponics like fluid) as nutes?
 
I grow with a light cycle 17 hours on 7 hours off.  This works well for me.  I often notice a lot of new growth in the morning (I wake up around the time that that the light turns on) so it appears that the rest peroiod is important.
 
Pfeffer said:
I do have professional measuring equipment (titan atlas 5) and can provide a protected enviroment (greenhouse + large propagator). But I can't find the values, but if I understand correctly you have experience with co2 fertilizing?

Will anything above average will provide a boost or will I need to stick to a certain range?

What humidity range would be good? And I figure a frequent but dilluted (i.e hydroponics like fluid) as nutes?
Click to expand...
 
 
I have experience using and dialing in CO2 propane and natural gas generators, though I now consider it to be inferior (in sealed) to running bottles. I've not done the math yet to see if bottles work on scale, or if the increase in price is dwarfed by reduced heating costs. What are you refering to by "values"?
 
There is no definite range, (beyond keeping below 1500ppm), any CO2 supplementation will prove beneficial. If the supply is inadequate to the plants consumption, it will provide a limited, but helpful boon. This is usually the result of chemical reactions/yeast for CO2, and the amount of material needed to supplement a greenhouse would be mind boggling. Winter greenhousing with combustion CO2 would be nice in Europe, but come summertime..
 
Oscillating fans to evenly mix the air (CO2 settling) and disturb canopy (O2 can "pocket" beneath leaves) are important. A sealed environment will provide the best results, maintaining the room at 60% RH at 85-86*F is ideal. Hydroponic/soil-less feeding is preferable.
 
I highly recommend researching on ICmag (anything Spurr has to say is gold), there is a vast amount of information there, and much more experienced/knowledgeable CO2 users than myself. More than likely, you're going to run in to issues and I'm not the person for troubleshooting.
 
Edit: Oh, and to totally contradict what I think with what I do - If you light proof your pepper grow/venting and have it in your bedroom, the plants feed you and you feed them :rofl:
 
My co2 is naturally 400+ppm 250-300 is low, the only practical ways to add co2 to a reasonable level are bottled co2 or propane burners. You could just increase ventilation.
 
I "vegged" the chillies up under 16/8 then they were moved under 12/12 and we saw an imediate onset of flowers over all the strains (Only some had flowers developed whilst under 16/8)
 
I intend to repeat this next grow only with a control room so I can better guage the effect of 12/12 on chillies.
 
Circadian rythums have a big effect on plant maturity I would suspect 24/7 would delay the onset of flowering.
 
Sealing a room means air conditioning there are ways to reduce this but most are beyond the budget or even practical for a home user. If I do fit CO2 I will use water cooling but I can fit radiators outdoors and cool my reservoir overnight when temps are low this will only work till March/April.
 
the ultimate way to cool a co2 grow would be a swimming pool.
 
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