photosynthisis stops at 95F

[Oxygen_Man]

found this ceintific article on global warming and took this snippet of text out of it to share. might be useful. "Photosynthesis starts to shut down at about 35 degrees C [95 degrees F], and plants often start dying at temperatures above 40 degrees C [104 degrees F]," Wignall said. "This would explain why there's not much fossil record of plants at the end-Permian— for instance, there are no peat swamps forming, no coal-forming whatsoever. This was a huge, devastating extinction."

 

[DevilWeedSeeds]

Interesting, I wonder how cold it has to be for photosynthesis to stop on the other end.

 

[supermanlives]

they did studies on corn and sunlight and temps . sounds about right

 

[señorsloth]

this is very interesting! it equates well to indoor gardening where temps are a variable we can control, unlike outdoor temps... it becomes even more prudent when we think about how much airflow plants get outdoors compared to most indoor grows...nothing can really compare... However, i don't think it's reasonable to deduce that all plants respond to temps equally...i mean it just would make no sense at all if the photosynthetic rate of plants in the Siberian tundra are the same as desert mesquite trees or thick, rainforest canopy's...

there are many places in the world where it is regularly well over 95 degrees and there are even lush rainforests in many of these places...frankly Minnesota had a record corn crop this year, it was disgusting out! humidity like crazy, over 90-95 almost every day, and even a few days that hit one hundred...the only reason the southern part of the grain belt didn't receive record numbers was equated to lack of water, not too high of temps, although that obviously contributed to lack of water...nevertheless it says to me that even corn can produce well in high heat, as long as provided with sufficient water.

and as for pot, well my ac broke this spring, i grew several fairly low quality crops because of it...but i did still yield, and temps were 95-105 every single day...if photosynthesis had stopped, i would think they basically would have died, surely it must have slowed, as the study above said it would, but i would be willing to bet the amount that each species of plant slows photosynthesis and at what temps they begin to slow must vary based on where they evolved to live... and maybe the reason buds grown in too high temps get lankier and fluffier, to allow more airflow and respiration, to cool down the plant so that it can start producing energy at a higher rate...

i am not a scientist, but those studies were probably done on temperate plants, evolved for a slightly colder area...marijuana is, for the most part, a tropical plant, and i would think most strains would contain genetics from some of the hottest places on the planet(barring deserts where nothing grows), Thailand, Vietnam, India, Pakistan, Afghanistan, and China...i would think that if pot evolved to live through Indian heat and Vietnamese humidity, it could handle most cabs...

it's an interesting point though, it explains why temps over 90 produce lankier plants with fluffier buds, but i think we are afforded a small bit of leeway just for the fact that we are gardeners of a tropical plant, we're not trying to grow a forest of bonsai maple trees(although wouldn't that be awesome?! id be in there playin' army guy all day long!). ive always said, keep those temps between 75 and 85, with no more than a 10 degree drop at night and you will be golden, the smell is the first thing to go with over hot buds, you will find that around 90 you start to lose smell, and at 75 the floral bouquet is at it's strongest...growth also seems best around 75 to 80...

i watch the tips of my leaves, when the serrations start to curl upward i know i'm right at the threshold of too hot, and unless it happened after an unusually hot day i usually move them a few inches farther away from my light. when the blades start to canoe, you have gone too far, and quality will be lessened if they are allowed to stay at these temps for too long...that's where strong airflow comes in, the bigger the fan, the closer you can put your buds to the light, and the better yeild you will receive. i think im at around 8 inches from canopy to light, but i don't really pay attention to that...i draw a line on my panda paper with dry erase marker to show where the heat is too hot to move any closer...

anyways ive been sober almost a week now and i have way too much energy, i'm sorry for polluting your thread with my retarded long ramblings...its a good thread! very relevant compared to a lot of the links people find!

 

[hempfield]

Interesting, I wonder how cold it has to be for photosynthesis to stop on the other end.

Freezing point perhaps ?

 

[SeaMaiden]

Whoa.... The Great Dying, indeed.

So, reading this:

Coal combustion

Studies earlier this year found evidence of a compound called fly ash, one of the products of coal combustion, in rocks laid down right before this extinction event. The finding suggested a large amount of coal had combusted over a period of tens to thousands of years.

The researchers already knew a series of volcanic eruptions, which gave rise to a region of volcanic rock called the Siberian Traps, occurred around this time and covered up to 2.7 million square miles (7 million square kilometers) in lava. These lava floods, made of molten basalt rock, could have taken out the animals and plants directly in their paths. To have any global impact, however, the volcanic eruptions also would have needed to send airborne ash, soot and gases high into the atmosphere, the researchers noted.

Coal also seems to have been present in the area of the Siberian Traps, and the researchers thought that perhaps the lava burned up a large amount of coal and left the fly ash — but they weren't sure whether it was physically possible. They ran computer simulations of these processes and found evidence that a coal explosion could have been the cause of worldwide climate change and the Great Dying.

I find myself wondering how anyone could insist that man's burning of fossils such as coal and oil could not have an effect, let alone similar? We're not calling this the Anthropogenic Age for nothin'!