Why plants need a dark period....

I wanted to come up with some conclusive evidence of why plants need dark periods. Mine go a touch yellow and slow in constant light, kind of like when a seed germinates and its cotyledons are yellow till it hits the light or when you put a green plant in a dark room for three weeks and it comes out the same just yellow. The kind of yellow that isn't caused by nutrient imbalance or enviromentals just lack of light.

The reason for the yellow colour is due to etioplasts which with light reform into chloroplasts and without light chloroplasts reform back to etioplasts. Etioplasts are yellow in large enough quantities like leaves and more see through white in stems with lower chloroplast concentrations as less etioplasts are formed from these low number of chloroplasts, again why a plant in a dark room may develop yellow leaves and whiter stalks.

I seen that light sugar hormones etc can stress the chloroplasts to revert to etioplasts and a link to suggest excess light or long periods of light can be such a stress.

So if i run 24/0 with my plant in constant light the yellowing of leaves i see can be attributed to light stress.

It goes onto state that there are a whole family of plastid which serve as organelles with purposes involved in starch/sugar conversion, fats, hormones and vitamins which under 24/0 light get overworked and can cause the other stresses that cause the green chlorophyl to revert back to yellow etioplasts.

I just want to throw this out there as a reason no dark period MAY cause slow growth and yellowing of leaves in places of high photosynthesis and probably get zero response as its out of my depth a bit. I leave a basic wiki link and excert from it for those that hate links



http://en.m.wikipedia.org/wiki/Etioplast















*Etioplasts* are chloroplasts
that have not been exposed to light. They are usually found in flowering plants
(Angiosperms) grown in the dark. If a plant is kept out of light for several days, its normal chloroplasts will actually convert into etioplasts. Etioplasts lack active pigment and can technically be considered leucoplasts
. High concentrations of etioplasts will cause leaves to appear yellow rather than green.[1]

These plant organelles
contain prolamellar bodies, which are membrane aggregations of semi-crystalline lattices of branched tubules that carry the precursor pigment forchlorophyll
. The prolamellar bodies are often (and presumed always) arranged in geometric patterns.[1]

They are converted to chloroplasts via the stimulation of chlorophyll synthesis by the plant hormone cytokinin
soon after exposure to light. Thylakoids
andgrana
arise from the prolamellar bodies during this process.

They don't need a dark period.

churchhaze said:

They don't need a dark period.

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If your talking about the plants ability run its calvin cycle under constant light then no it dosent need a dark cycle.

If your talking about achieving maximun growth for both phot and auto flowering plants then there are a lot of previous well conducted experiments that show 20/4 to give optimun growth and this is especially prevelant in the autoflowering community where this is pretty much set in stone.

I dont disagree with you as you can see but i do when it comes to optimun photoperiod.

2Hearts said:

If your talking about the plants ability run its calvin cycle under constant light then no it dosent need a dark cycle.

If your talking about achieving maximun growth for both phot and auto flowering plants then there are a lot of previous well conducted experiments that show 20/4 to give optimun growth and this is especially prevelant in the autoflowering community where this is pretty much set in stone.

I dont disagree with you as you can see but i do when it comes to optimun photoperiod.

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I don't know much about growing autoflowering strains, but when it comes to vegging, more experiments have shown that 24:0 provides marginally better results than 20:4. The main reason to use 20:4 is to save power, since you aren't really losing much in terms of growth. I don't notice slow growth at 24:0 at all.

If MJ is left in a dark room, the new growth can not sysnthesize chlorophill, that's why they appear yellow/white...

MJ uses photoperiod to undertand when winter is coming, that triggers flowering, to prepare for the next season it produces seeds and die...

If you go 24/0, it will continue to veg, old leaves will get yellow and fall, but new green leaves flourish... MJ is a Type C plant, it does not need dark for veg. Hope this helps....

CenkTripper said:

If MJ is left in a dark room, the new growth can not sysnthesize chlorophill, that's why they appear yellow/white...

MJ uses photoperiod to undertand when winter is coming, that triggers flowering, to prepare for the next season it produces seeds and die...

If you go 24/0, it will continue to veg, old leaves will get yellow and fall, but new green leaves flourish... MJ is a Type C plant, it does not need dark for veg. Hope this helps....

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If you read the wiki link it will explain briefly that an unsynthesizing chloroplast or group term chlorophyll has a very good chance of converting to or being an etioplast of which in large enough quantities look yellow. This seems to be the science behind it id say as best i know.

churchhaze said:

I don't know much about growing autoflowering strains, but when it comes to vegging, more experiments have shown that 24:0 provides marginally better results than 20:4. The main reason to use 20:4 is to save power, since you aren't really losing much in terms of growth. I don't notice slow growth at 24:0 at all.

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I didnt find that when i ran 24/0 plants seemed smaller, extrodinary short internode growth and pale yellow minor discolouration particuarly to new growth but here we reach an impass because the jury is split and i nay take sides except what ive seen and read in tests conducted many times over. I changed nothing but light cycle and got two different responses, dark period gives me better growth all over and greener leaves. Clones too are recomended dark periods and this is well known for a large group of growers. If 24/0 does best for you then thats great but hey i wasnt looking for a one or other is best just a reason behind it.

Yes you can cite the calvin cycle but can you cite stresses that may affect it. Too bright lights cause chloroplast oxidization, extended periods of light affect the whole plastid organelle family which is thusly intertwined witC3 plants calvin cycle and therefore a consideration for wether plants need dark cycles.

CenkTripper said:

MJ is a Type C plant, it does not need dark for veg. Hope this helps....

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Mj is a type C3 plant, the C stands for carbon which plant process and the 3 stands for the particular part of the carbon cycle calvin cycle it uses to process it. There are also C4 and CAM plants which obtain carbon like a cacti which uses the dark period to take in Co2 as the day is just tooo damn hot and would loose water too quickly. Its a complex subject of which i need to school up on again.

2Hearts said:

I didnt find that when i ran 24/0 plants seemed smaller, extrodinary short internode growth and pale yellow minor discolouration particuarly to new growth but here we reach an impass because the jury is split and i nay take sides except what ive seen and read in tests conducted many times over. I changed nothing but light cycle and got two different responses, dark period gives me better growth all over and greener leaves. Clones too are recomended dark periods and this is well known for a large group of growers. If 24/0 does best for you then thats great but hey i wasnt looking for a one or other is best just a reason behind it.

Yes you can cite the calvin cycle but can you cite stresses that may affect it. Too bright lights cause chloroplast oxidization, extended periods of light affect the whole plastid organelle family which is thusly intertwined witC3 plants calvin cycle and therefore a consideration for wether plants need dark cycles.

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I can assure you your leaves were not yellow because of 24:0 light. Seeing a green and healthy plant under 24:0 lighting should be enough to convince you that 24:0 lighting does not cause yellow leaves. I've never noticed a correlation between leaf color and 24 hour lighting.

I run 24/7, never seen yellowing.

Its just a freaking weed & nothing else! it will grow under the harshest conditions & thrive under the best!!! But if you don't fuck it up from seed to seedling it will produce no matter what. I run 24/7, never seen yellowing. Autos were created so even the most inexperienced growers can just germ in the same container & finish without doing anything other than water, feed, pull, trim & harvest!!!

johnny961 said:

Its just a freaking weed & nothing else! it will grow under the harshest conditions & thrive under the best!!! But if you don't fuck it up from seed to seedling it will produce no matter what. I run 24/7, never seen yellowing. Autos were created so even the most inexperienced growers can just germ in the same container & finish without doing anything other than water, feed, pull, trim & harvest!!!

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Sorta, i think autos were created for fast harvesting in short seasons lol.

churchhaze said:

I can assure you your leaves were not yellow because of 24:0 light. Seeing a green and healthy plant under 24:0 lighting should be enough to convince you that 24:0 lighting does not cause yellow leaves. I've never noticed a correlation between leaf color and 24 hour lighting.

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Ok i think this debate goes a little futher than who likes what light period...

Many C3 plants show necrotic chlorosis from continuous light e.g. The well studied tomato plant, try this type of C3 tomato under 24/0 and yes you get yellowing.

My point is what makes people sure that 24/0 is stress free to mj plants and can you describe the biology behind your reason?

Till then your just another grower with an opinion just like me and another uninsightfull post on photoperiod.

Years ago I did a side-by-side using 3 different light cycles in veg.
24/0
20/4
18/6

20/4 yielded the best overall.
18/6 was 2nd best.
24/0 was last.

Did it again a year or so later with exact same results.

I would never use 24/0. The plant may survive, but it hurts the overall potential in the end.

johnny961 said:

Its just a freaking weed & nothing else! it will grow under the harshest conditions & thrive under the best!!! But if you don't fuck it up from seed to seedling it will produce no matter what. I run 24/7, never seen yellowing. Autos were created so even the most inexperienced growers can just germ in the same container & finish without doing anything other than water, feed, pull, trim & harvest!!!

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Autoflowers grow best with a dark period and yeild more that way. This is a hard fact in the autoflower forums if you ever hang there.

althor said:

Years ago I did a side-by-side using 3 different light cycles in veg.
24/0
20/4
18/6

20/4 yielded the best overall.
18/6 was 2nd best.
24/0 was last.

Did it again a year or so later with exact same results.

I would never use 24/0. The plant may survive, but it hurts the overall potential in the end.

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Yes and as i have said this experiment has been run hard many times in the autoflower community.

This is not a debate which is best, If Church Haze does better with continuous light then i applaud him not get a group of peeps who disagree to bash his methods.

If we had all the answers we may find certain strains do better than others thus validating growers who use this style.

What i want is a more concise picture of whats going on in the plant and i cite tomato plants as C3 carbon cycle plants the same as mjs carbon cycle that hate continuous light and show stress in necrosis and yellowing.

I too have run this experiment with tomato and mj plants and i found a dark period was better, the tom plants changed from purple veined dull leafed to shiny vibrant healthy plants in under a week and my mj plants looked better by far in the same period but way more noticable on tom plants.

althor said:

Years ago I did a side-by-side using 3 different light cycles in veg.
24/0
20/4
18/6

20/4 yielded the best overall.
18/6 was 2nd best.
24/0 was last.

Did it again a year or so later with exact same results.

I would never use 24/0. The plant may survive, but it hurts the overall potential in the end.

Click to expand...

I have read where several people have tried this same comparison, and funny thing is the final result/conclusion is always the same, 20/4, then 18/6 and 24/0 is last

can never figure out why people would run 24/0 unless cold temps are a factor.... it's another myth that people refuse to let go of

I run 18/6 during peak summer to help cool down at night, otherwise I am 20/4 all the time.

ISK said:

I have read where several people have tried this same comparison, and funny thing is the final result/conclusion is always the same, 20/4, then 18/6 and 24/0 is last

can never figure out why people would run 24/0 unless cold temps are a factor.... it's another myth that people refuse to let go of

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Is easy to figure out the reason that people run 24/0, it is a simplistic view of the carbon cycle in C3 plants whereby chloroplasts need no dark period and can run 24/0 thus more energy, sugar and hence quicker growth. This point i agree on but.....


.....it fails to take into account all the other stuff that could hinder continuous light cycles like hormone production, startch storage, atp production, oxidization and all the other cycles that interplay with the C3 plants carbon cycle.

On this simplistic view all C3 plants require no dark period but there are literally hundreds of examples showing that its a little more complicated than what we think.

Again we see this in experiments from many many growers who have come to shun 24/0 and love 20/4.

Mess with any system in a plant and energy production changes, continuous light can certainly do that as cited.

I've done 24, and I've done 18-20 hours of light.

Strictly anecdotal, just my observation, but a few hours sleep each night helps. Better color, shorter internodes, just healthier plants. Not too worried about the $ savings.

I run them 24 for about 5 days after the seedlings emerge (don't clone) then I go to about 4 hours dark each night. When I get up to piss about 3am I turn them off and they sleep till sunrise.

Anyway it seems to agree with them.

I think different strains might react differently to different light schedules. In any case all genetics are based on a plant used to at least a few hours of darkness in nature.. Seems to me they appreciate the nap.

Meh,this knowledge doesn't give me bigger buds