Raising my first thread from the dead huh, shutupdonny. I see you, breh. :banana1sv6:

I had always run 24/0 until I read the thread on that other forum that Smokestack linked to, but after reading it I switched to 18/6 and have been getting better growth (no side by sides though). About 75% of that thread was idiotic bickering, but the other 25% was well documented research. Heres the take home message:

A dark period during veg is benificial AS LONG AS YOUR PLANTS ARE GETTING ENOUGH PAR DURING THE LIGHT PORTION. So if you're just running a couple hundred watts of flourescents for a medium sized veg room you should keep them on 24 hours as they will benefit more from the extra hours of light than they would from the metabolic changes that accompany a few hours of dark. IF however you have a fairly large amount of light for your space (my main veg room is just a 2x3x7 tent with a 400MH then they get plenty of light during 18 hours and its best to give them some dark for a while.

I just saved you from reading a 42 page thread.

Ne Obliviscaris said:

They don't say anything about there being a ceiling on the quantity of DLI that is usable, however. Can you link me to the sources that stated that, or the thread where it was discussed?

Thanks.

Click to expand...

I'll chime in. The processes using light depend on a litany of changing conditions: available resources in the cell, concentrations of those, concentrations of necessary enzymes, concentrations of inhibitors/activators/coenzymes/etc. Let's assume for a second that all of these are constant. Under these conditions there is a rate constant K which dictates the speed of the reaction wherein chlorophyll/carotenoids absorb(s) a photon and begin(s) electron transport. There are similar rate constants controlling the next electron acceptors and enzymes further along in the chain. This is much more complex and depends much more on the concentration of reactants in the cell, and it is likely that the concentration of photons-- umol or micromoles--has a similar effect.

Micromoles measure concentration-- its typically given as molarity of photons per unit area. Even without all the more complex effects, there is a maximum number of photons a plant can absorb per day--and this number is related to to the amount of active chlorophyll/carotenoids in the plant, the absorption rate of those molecules , and probably local concentration of photons--its actually pretty hard for a photon to have the correct energy to activate chlorophyll. Many are lost/have the wrong energy/bounce off of other inactive molecules). Must also consider the various factors controlling the subsequent reactions--especially the one where chlorophyll donates an electron after absorbing a photon. It is likely that the protein responsible for this is controlled by feedback inhibition by products later on in the process of photosynthesis.

TLDR:

Due to physical limitations of the chemical processes involved, there is a maximum photon absorption/day for any plant.

Hope that helps.

:confused0059:

ShutUpDonny said:

Who you calling a novice grower ML?! :D

I'm going to start it up again in a few weeks with my new fem Haze seeds. If I get males or hermies this time I'll let people know about it, but otherwise I was psyched with the response. They absolutely exploded once I went from 24/0 into the Gas Lantern, and now that I know how to really take care of my ladies (RH in particular) I'm hoping for great things.

Count me as supporting 12/5.5/1/5.5, though I've yet to try the tapering light down during flower.

Sorry for zombie posting.

Click to expand...

just to clarify for everyone else you are speaking of 12 on, 5 1/2 off, 1 on, 5 1/2 off to maintain a vegetative cycle. I'm going to switch up to this soon here myself.