Phillybonker
Well-Known Member
I know if temperatures drop down too far it can have a negative effect on seedlings, but my question is why does cold temperatures have a negative effect on seedlings?
Why are cold temperatures bad for seedlings?
- Thread starter Phillybonker
- Start date
Hi PB - because it prevents leaves from transpiring, thus depriving them the ability to process nutrients
I think
I think
Delps8
Well-Known Member
Cold temps slow down all metabolic processes and colder temps can reduce uptake of certain nutrients.
Cars in Minnesota don't use 10W30, right?
Cars in Minnesota don't use 10W30, right?
Excuse me for being British, but what the fuck does that mean?
budnoob3
Well-Known Member
Don’t try to grow in a car in MN??? 
budnoob3
Well-Known Member
As far as I know, colder temps will trap some chlorophyll and sugar preventing or at least slowing transfer of nutrients and sugar which contributes to purpling of leaves and older growth dying off more quickly (think 2nd week of Oct in VT). I’m kind of skeptical on the cold harming seeds in any way because Mother Nature drops many seeds in Fall that are just fine come spring time. I also understand that a plant native to Thailand for example might produce seeds that have much different tolerances so I’d recommend attempting to emulate the original environment of the strain. In the case of hybrids, I’d try to emulate the breeders environment as closely as possible.
I was wondering that myself and I ain't even British. This has to be one of your better comments in the time you have been a member
.
It’s a bit of a stretch for a comparison but it sort of works… The viscosity of your motor oil needs to be different when living in a frozen part of the country. Otherwise your oil will have problems lubricating correctly until it gets to engine temp which takes forever if it’s frozen outside. 10w-30 is made for warmer climates like California.
People store their seeds in the fridge or freezer all the time. As far as seeds themselves go, temps don’t matter as much. I don’t think that was the question here.
But once they are growing, there is a temp range you’d probably not want to drop ( or rise) into because it screws your VPD up completely among other things.
I mean for some of the same reasons, humans don’t keep their houses 50F on the inside. If you did, everyone would have circulation problems and constant colds, the house would likely rot from uncontrolled humidity and the only thing that grows in that temp range is fungus.
Plants have an operating temperature. Just like most things. Operation outside that range is something proven unsuccessful for thousands of years through farming and agriculture.
There’s a much more scientific reason but basically….That’s why.
Delps8
Well-Known Member
Got a laugh out of that!
Got the numbers bass ackwards - 5W30 vs 10W30 viscosity in cold weather.
Delps8
Well-Known Member
Plants can't control their internal temperature the way a mammal can. Same with reptiles.
This is the graphic from the Chandra paper that every quotes (well, used to quote) saying that there was little value in running high PPFD. It shows the net photosynthesis values as temperature and PPFD vary.
For this issue, check out the different in net photosynthesis as temperature goes from 20° (68°F) to 25° (68°F) - it looks like it goes from 7 to 14. Temperature is a BFD for plants.
The issue with light levels is that Chandra measured net photosynthesis from a small sample of leaves. To me, I'm not interested in harvesting net photosynthesis so I didn't get caught up in it but to a lot of growers it was proof that there was little value in growing at light levels above 500µmol. As research has shown, there's no validity to that argument - crop yield increases in an almost linear manner as light levels increase.
Not sure what your point is by saying that, I was making a simple comparison, not stating any science.Plants can't control their internal temperature the way a mammal can. Same with reptiles.
This is the graphic from the Chandra paper that every quotes (well, used to quote) saying that there was little value in running high PPFD. It shows the net photosynthesis values as temperature and PPFD vary.
For this issue, check out the different in net photosynthesis as temperature goes from 20° (68°F) to 25° (68°F) - it looks like it goes from 7 to 14. Temperature is a BFD for plants.
The issue with light levels is that Chandra measured net photosynthesis from a small sample of leaves. To me, I'm not interested in harvesting net photosynthesis so I didn't get caught up in it but to a lot of growers it was proof that there was little value in growing at light levels above 500µmol. As research has shown, there's no validity to that argument - crop yield increases in an almost linear manner as light levels increase.
The question is ‘why are cold temperatures bad for seedlings?’
I said plants prefer a certain temperature range to live in, just like humans. Right?
So WTF are you talking about?
Delps8
Well-Known Member
I've added explanatory text below and I understand that you were making a comparison.
"not stating any science" - OK
Understood.
Yes.
Sorry I wasn't clear.
"Plants can't control their internal temperature the way a mammal can. Same with reptiles."
Seedlings are young plants and plants can't control their temperatures the way mammals can. Reptiles are the same - they can't control their internal temperatures.
I added that information to provide a sense of "scope" - heh, mammals can stay warm but plants can't.
And to provide additional information, I provided research data that shows how plant "growth" is impacted by temperature. Since seedlings are plants and we're discussing cannabis plants, a discussion of how change in temperature about cannabis plants is pertinent to how seedlings are impacted by temperature.
Didn't mean to cause a row. Just trying to help the OP understand that temperature impacts plants and, by providing information from a research paper, my intent was to show the OP that just changing the temperature from 68 to 77 degrees will double the rate of photosynthesis. That is significant and I though he might find it helpful.
Understood and that’s good info, I appreciate it.
Sativa1970
Well-Known Member
Metabolism is just chemical reactions. Temp is a major factor in reaction rate. Some people and mother nature chill seeds to slow the metabolism, saving more energy for when it is time to sprout. Seedlings have limited roots and leaves with a lot of energy needed for growth. Warmer temps increases the reaction rate, increasing metabolism, allowing them to make the most glucose possible. Just what a growing girl needs.
Delps, put the pipe down when working on your car!
Delps, put the pipe down when working on your car!
From @Delps8
We can place all the nutrients, minerals, and water we want in the soil or hydro system and it will not make any difference. The plant does not live directly off of these nutrients, etc. If the plant cannot get the right light wavelengths and go through photosynthesis it cannot produce the sugars needed to feed itself.
Plants are the only life on this planet that makes or produces its own food. All other life directly or indirectly feeds off of the plants. If all the plants on this planet were to die then all the other life forms would eventually starve.
This that Sativa1970 mentions. Warmer temperatures that fall within the optimum range help push the photosynthesis rate to maximum. For the most part each specie of plant has its own optimal temperature range which is why we see some plants starting to grow in the very early weeks of spring and they will soon stop when it gets warmer during the days and nights.
We can place all the nutrients, minerals, and water we want in the soil or hydro system and it will not make any difference. The plant does not live directly off of these nutrients, etc. If the plant cannot get the right light wavelengths and go through photosynthesis it cannot produce the sugars needed to feed itself.
Plants are the only life on this planet that makes or produces its own food. All other life directly or indirectly feeds off of the plants. If all the plants on this planet were to die then all the other life forms would eventually starve.
Not true. Plants do control their leaf temps by opening and closing their stomata in response to temps and humidity. VPD and all that.
Sativa1970
Well-Known Member
Stomata opening with heat would be like a minor sweat. Maybe a deg or two cooler. Closing the stomata won't generate any heat. Defiantly not like mammals but better than reptiles.
Delps8
Well-Known Member
Plants do not control their internal temperature by using their stomata. They can release moisture which may cool the plant. That's not "controlling their internal temperature".
My statement was pretty basic "Plants can't control their internal temperature the way a mammal can. Same with reptiles." and that's because one of the fundamental differences between mammals, reptiles, and plants is that mammals have a much greater ability to control their internal temperature than plants and reptiles can.
