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| In another post I read photosynthesis stops at 104 degrees F. Just using google I have found references to the stop and one site even seemed to say 98 degrees.
Anyone have a good link for me about this? Also does the switch get thrown where the plant produces every morning then around noon get shut down? Thanks in advance. |
Follow-Up Postings:
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| I posted that earlier this week, but others may have noted it in conversation about the historic heat wave. For tree people, I think the more important factor is drought, migration of insects into new areas, and other more mundane issues. Back to context of the heat waves, here's a 2005 BBC spot how plants become producers of CO2 in heat waves (like the one they had in 03 in particular) Another good one is http://www.agu.org/pubs/crossref/2008/2008GL034071.shtml Some 100 year models put variants in some places at 50C extremes (rather than the extreme 40C/104F) . The real 40F problem is grain crops, IMHO. Most recently, a blog post (cross posted on several blogs) pulled up the photosynthesis discussion due to the recent US heat wave. This one (and other recent ones) are rather different due to long period of sustained 100+ temperatures and little rain and very warm night time lows. Farmers also have to irrigate crops they know they can't keep alive during these conditions or they'll be denied crop insurance claims, so they're getting deeper into prehistoric water that can't be replenished... So it's not just the slowdown/stop of photosynthesis, although that's an interesting point. Like everything else, it's a combination of factors. Don't worry though, According to NCDC, the odds heat wave of this occurring randomly during any particular month are 1 in 1,594,323, based on the climate we knew. :-) Bottom line, plant trees, as many as you can safely manage. I prefer big ones. :-) |
Here is a link that might be useful: blog, bit of hyperbole, but good links to back it up
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- Posted by ken_adrian z5 (My Page) on Tue, Jul 10, 12 at 22:08
| how does one differentiate on water stress and the stopping of Photosynthesis if it cant pump enough water.. does the leaf suffer or die.. from Photosynthesis stopping .. or due to lack of water??? ken, who didnt read any of the links.. lol ... is there a real short answer to that quandary??? |
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| Ken......it's hard to explain but the reasons are enzymatic. All plants do not photosynthesise in exactly the same manner, but all are affected by heat and the decline in photosynthesis is impacted on a chemical level by a slowing down in the Calvin/Krebs cycle by how certain enzymes interact. It's not a specific stop-point and the magic degree number can be impacted on the rapidity of the heat rise, and the type of plant. Trees have 'reserves' and that's why really nasty summers set them up for poor winter tolerance. The carb reserves they normally build up in summer is depleted instead of replaced in preparation for dormancy. Hogmanay is spot on, in that it's a major issue for grain crops and although an issue with trees, probably less important in the here and now than water stress and associated disease/insect pressure on the stressed trees. |
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| Ran across an article sometime ago stating that Arizona Cypress are successful in growing and thriving in hot dry desert-like conditions, because the trees essentially can go into a sort of hibernation during the summer. Their stomata were very efficient at achieving near total and complete shut-down of transpiration under unfavorable conditions of heat and water-stress. Don't remember any specific temperatures mentioned. Apparently they are much more successful at it than most other trees. Last year during the worst ever heat spell recorded in Texas coupled with one of the 5 worst dry spells, both the Eastern Red Cedar and Asheii Junipers in this area suffered noticeable losses. Not one established specimen of Arizona Cypress succumbed down here. (note however that all specimens of Arizona Cypress in this part of Texas are planted trees). |
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| There will probably be a host of peer reviewed work on this years climate and impacts. We just have to wait.. |
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| hogmanay, the 1 in 1,594,323 stuff is statistical trash. Look at the link below: Also, read up on the history of the 1930's dust bowl/heat/drought. |
Here is a link that might be useful: Quote of the Week � Master meteorologist heat wave FAIL
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| I dont tilt strawmen. |
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- Posted by strobiculate none (My Page) on Fri, Jul 13, 12 at 14:32
| this exact question was asked over the winter in reverse...about how plants cope with winter drying winds. simple answer is, just like people, plants struggle to cope with the extremes that weather can provide. and like people, some plants are better at dealing at certain stimuli than others. in part, this is how we develop various cultivars. of particular interest to you may be the difference between c3 and c4 plants. as to why it stops...er, slows does markedly, it's a way for the plant to conserve resources. as to the trigger that does it and how those triggers may vary...that's a different discussion |
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