Understanding Transpiration

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Ignignokt

Ignignokt

This got me also thinkin' bout the carbon cycle - https://en.wikipedia.org/wiki/C4_carbon_fixation

I'm still somewhat fascinated by the results I've seen with CO2 enrichment in the presence of high Mol output light sources. The transpiration (normal) model shifts as the carbon / water ratio is 1:4 so you end up with lots moisture to remove from the enclosure if CO2 level is not a limit. I use 1200-1500ppm with elevated temperatures in vegetation to gain mass.
 
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Can you explain more about the CO2 enrichment, how do you do that? How do you measure, what were your experiences?
SpiderK also mentions:
"Unfortunately, much more water leaves the leaf than CO2 enters"

Does that mean we have to add to the water co2 and o2?
o2 for the roots
co2 for the leaves

I assume transpiration, in normal outside growth, is limited by soil compaction similar to if you tried to suck through a straw that is plugged with something and in hydroponics you do not have that problem (unless wind and RH/Temp). It would be interesting to find some hybrid solution between outdoor and hydroponics. Say you could levitate a piece of earth to "unblock the straw" yet supply it constantly with water of high concentration of O2 so that the roots dont suffocate and CO2 for the leaves. Although couldnt it get the carbon from coal ?
 
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Sorry not coal but maybe molasses, so the bacteria farts the carbon into the plant ?
 
Douglas.C

Douglas.C

The "VPD" information everyone is using says I flower in 18+.

Like SpiderK says "Trichomes (hairs) - create a more humid microenvironment to reduce evaporative water loss"

What trigger causes more trichomes to be produced, by trichome bearing plants? Low humidity.
This is actually incorrect. Turns out the humidity is not a 'trigger' to grow more trichomes, I'm really growing less plant under the same number of trichomes.

I flower with a canopy temp of 72F max (cannabis will try to cool itself using transpiration in higher temps), and a relative humidity between 20-25%, I prefer 20%. This low temp, low humidity sets up some rather high transpiration rates, making for much lower nutrient strengths being necessary. Yes, I grow hydro, no 'lack of moisture' in my soil. :)

What do I get? Massive trichome density and outrageous terpene/cannabinoid expression. Every time I hear a grower complain about how hot it is in their flower room I cringe. When I sample their cannabis I just shake my head sadly. So much effort, for such a lower quality product.

Douglas
What I do get is what other growers who've done the same agree on. I get higher terpene production and retention. Since you're growing less plant, you have to veg longer than you would in a super-high VPD environment as you're not going to get that massive explosion of growth during stretch.

I've been meaning to fix where I've posted the "humidity is a trichome trigger" for some time now. Apologies for being late.
 
CannaNovice

CannaNovice

The rosenthal book is a good starting point, IMO, but 50% isn't doing you any favors. My best rounds have been when rh was 70%, temps around 80 and then the temp and rh tapered back to low to mid 70s and 50% by the end.
Im following these guidelines I read somewhere along the way, maybe royal queen seeds page? SEEDLINGS CUTTINGS
Can you all make some recommendations on ideal humidity and temperatures? I read one of Ed Rosenthal's books, and if IIRC, he recommends temps for flowering plants of 75-80deg, with humidity around 50%.

I just completed my first indoor organic soil grow, and the leaves on my plants all started looking pretty sad when they got near full ripeness. Really, they never looked 100% happy. They have always had a reverse-canoe effect going on - edges curling down with end tips showing slight burning, and also claw effects. I figured it was Nitrogen excess.

Just last night, I had an "ah-ha!" moment when I realized that the fan I had blowing on my canopy was fixed (not oscillating), and may have been drying the leaves. Now I know that it may have been dramatically increasing transpiration. I live in a very dry climate. I've been running the house fan 24/7 to keep the room from getting too humid, and now I'm wondering if it's been too dry. RH stays around 50%. Dark cycle temps for grow room were dropping in to the low 60's, because it I run the dark cycle from 8:00am - 9:00pm, and I run A/C in the house during day. Makes basement cold.

Great thread! Thank you!

I think I found these guidelines at royal queen seeds faq paraphrasing heavily...
seedlings/cuttings 65-75% Rh 68-77F
Veg start to decrease RH weekly by 5% 65-70% RH 72-82F
Early Flower 40-50% RH max 68-79F (over 55-60% rh is bad)
Late Flower last (2-4 weeks) 30-40% 64-75F
Also read that if you can keep your grow room 5-10 degrees cooler for the first 2 hours of lights on, during flowering, this dramaticly reduces streching. Its hard to drop 5-10 degrees from lights off temps but pays off I have read.
 
Aqua Man

Aqua Man

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First time I have read this and yeah this is an amazing breakdown of not only VPD but complete information of other contributing factors that affect respiration.
 
noob12345

noob12345

yes I have never thought of deficiencies in that way before! I always assumed defs were because of user error with the nutes without a second thought of VPD and transpiration but when you think about it, it all makes sense! Lightbulb moment for me.




First time I have read this and yeah this is an amazing breakdown of not only VPD but complete information of other contributing factors that affect respiration.
 
Aqua Man

Aqua Man

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yes I have never thought of deficiencies in that way before! I always assumed defs were because of user error with the nutes without a second thought of VPD and transpiration but when you think about it, it all makes sense! Lightbulb moment for me.
I made a vpd thread a couple weeks ago explaining it in very basic terms and giving guidelines to the ideal VPD for different stages of growth no where near as complete as this. What I found interesting was that VPD is not as beneficial to growers using wet/dry cycles as it is to hydro and soiless. I had not really considered this before even though I have the understanding and it makes perfect sense.
 
noob12345

noob12345

You know aqua ive been struggling with various problems this grow, most of it turned out to be my co2 generator, thing is I changed it to vented and switched off the co2 and its better but now way too cool and humid, striking a happy medium seems hard, not really sure if the generator is causing a stomata closed situation. Its a proper dilemma tbh.




I made a vpd thread a couple weeks ago explaining it in very basic terms and giving guidelines to the ideal VPD for different stages of growth no where near as complete as this. What I found interesting was that VPD is not as beneficial to growers using wet/dry cycles as it is to hydro and soiless. I had not really considered this before even though I have the understanding and it makes perfect sense.
 
Aqua Man

Aqua Man

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You know aqua ive been struggling with various problems this grow, most of it turned out to be my co2 generator, thing is I changed it to vented and switched off the co2 and its better but now way too cool and humid, striking a happy medium seems hard, not really sure if the generator is causing a stomata closed situation. Its a proper dilemma tbh.
A burner? Have a diary that I can peek at maybe I can spot something
 
noob12345

noob12345

Diy watercooled burner, ill start a diary first thing and post a few pics something seems a miss in my groom though, ive never managed to make my groom work as well as the tents!


A burner? Have a diary that I can peek at maybe I can spot something
 
Aqua Man

Aqua Man

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When its on, they stop drinking and within 2 days start showing cal-mag def or P def and when its off they are ok but then its unsealed and too cold
My guess is ethylene... You need a very efficient method of burning. The CO2 burners sold are built for that purpose.
Take a peek here... Just plucked Haven't read it so I'm assuming it will explain it.

 
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