Temperature tolerance

[gonewild]

What biological factor causes a plant to not survive certain temperatures?

I'm not referring to plants being damaged by freezing but rather the opposite.

Why do plants from a cold climate die in a warm climate?

Is it the actual temperature or another factor?

 

[Ray]

Totally a guess on my part, but I'll bet metabolic rates play a role.

I picture a scenario in which the plant has to go through one set of physiological processes in order assimilate nutrients and (more importantly) produce the energy stores, and another set of processes consume those.

It seems plausible that two sets of processes have different responses to temperature, and it's fairly well established that plants' metabolic rates increase with temperature within a given range, so maybe the "consumptive" ones might outstrip the "collective" ones as the plant warms.

 

[ALToronto]

I have a masdevalia that's been struggling this summer. In the spring, all the leaves were dark green and blemish-free. Now, the leaves are pale and with lots of brown spots. I water daily, either with K-Lite or plain RO water, and still new growths are wrinkled.

It clearly "perspires" moisture, and even full shade and 70+% humidity can't compensate for the moisture loss. My husband revolts once the temp reaches 29 degrees and turns on air conditioning, but the house has been just below that level for most of the summer.

 

[Rick]

Proteins and enzymes are "designed" to operate in certain temperature regimes.

In plants those operational regimes are a lot broader than for poikilotherms, which are most narrow in homeothermic organisms. Just because of the degree of control the organisms have (or don't have) over the temperatures they are exposed too.

But you can certainly get down to the molecular level for temperature effects leading up to gross physiology effects. Including water balance and nutrient uptake rates.

http://www.ncbi.nlm.nih.gov/pubmed/12231821

 

[Rick]

I have a masdevalia that's been struggling this summer. In the spring, all the leaves were dark green and blemish-free. Now, the leaves are pale and with lots of brown spots. I water daily, either with K-Lite or plain RO water, and still new growths are wrinkled.

It clearly "perspires" moisture, and even full shade and 70+% humidity can't compensate for the moisture loss. My husband revolts once the temp reaches 29 degrees and turns on air conditioning, but the house has been just below that level for most of the summer.

Is the plant under lights or receiving natural light? Have you tried bumping up the Mg and phosphate?

 

[gonewild]

Proteins and enzymes are "designed" to operate in certain temperature regimes.

In plants those operational regimes are a lot broader than for poikilotherms, which are most narrow in homeothermic organisms. Just because of the degree of control the organisms have (or don't have) over the temperatures they are exposed too.

But you can certainly get down to the molecular level for temperature effects leading up to gross physiology effects. Including water balance and nutrient uptake rates.

Where in plants are these proteins and enzymes?
What causes failure when a plant grows 10 degrees to warm?
Is this something that might be overcome with nutrient balance manipulation?

 

[Rick]

http://link.springer.com/article/10.1007/s11099-012-0070-2

Here's another link.

Note that light and temp works together to screw up photosynthesis at the high ends.

 

[Rick]

Where in plants are these proteins and enzymes?
What causes failure when a plant grows 10 degrees to warm?
Is this something that might be overcome with nutrient balance manipulation?

The protiens and enzymes are in the cells. Certainly the chlorophyll is in chloroplasts which are structures inside the cells similar to mitochondria in animal cells.

I provided links to 2 papers that focus somewhat on the effects to the photosynthesis II pathway. Especially with folks seeing loss of green with summer growth. It does say that temperature ranges for the various enzymes can be enhanced by providing additional operating substrates for those enzymes, but the effects are not without limits.

 

[ALToronto]

Is the plant under lights or receiving natural light? Have you tried bumping up the Mg and phosphate?

The masdie is in an east-facing window, but I placed it at the south-most end of the windowsill, so it gets maybe 1 hour of early morning sunshine. I will try higher phosphate and Mg. Do you mean more Mg than K-lite already contains?

 

[Rick]

The masdie is in an east-facing window, but I placed it at the south-most end of the windowsill, so it gets maybe 1 hour of early morning sunshine. I will try higher phosphate and Mg. Do you mean more Mg than K-lite already contains?

I've cut may daily to eoday application of N to about 5 ppm N. I haven't applied a single weekly dose of >20ppm N in 2-3 months now.

Yes I made up a solution of MgSO4, MgPO4 and a dash of FePO4 and have been supplementing the dilute K lite with that for a couple months now, with very good effects. This is mix is very similar to a Dynagrow Bloom boost product if you don't want to make your own. Just calculate the use rate for around 5 ppm P.

I'm offering daily amounts of feed that I know would be ecologically relevant in healthy streams and creeks. total N is under 5 ppm, PO4 is 3-5 ppm, K is around 0.5 to1ppm Ca is around 15-20ppm and Mg around 4-5 ppm.

Even the big specimen plants are growing like gangbusters.

 

[gonewild]

The protiens and enzymes are in the cells. Certainly the chlorophyll is in chloroplasts which are structures inside the cells similar to mitochondria in animal cells.

I provided links to 2 papers that focus somewhat on the effects to the photosynthesis II pathway. Especially with folks seeing loss of green with summer growth. It does say that temperature ranges for the various enzymes can be enhanced by providing additional operating substrates for those enzymes, but the effects are not without limits.

How might atmospheric pressure come into play?
It seems that most orchids that need cold come from high elevation.
Maybe it is atmospheric pressure or the gas content of the air at colder elevations and not so much the temperature?

LOL, it's late and cold and I'm trying to think of something to think about.

 

[naoki]

In addition to what Rick said about enzymatic reaction, protein folding can be screwed up with too much heat.

http://www.sciencedirect.com/science/article/pii/S101836471000087X

Basically, these heat shock proteins (HSPs) could help folding correctly, but different plant species probably express this differently, which may lead to differences in heat tolerance. Now you might ask that plants can be heat tolerant if they can be expressed HSPs all the time. But there are cost (e.g. high energetic cost to synthesize HSPs).

 

[Ray]

I haven't applied a single weekly dose of >20ppm N in 2-3 months now.
(Text removed by RB)
Even the big specimen plants are growing like gangbusters.

I don't think that's enough time to connect one with the other. In fact, I'd speculate that the bigger the specimen, the more resources it can share, so the less effected it would be.

 

[limuhead]

Interesting topic. While I admit I don't in any way consider myself an expert about temperature ranges by any means I believe that leaf temperature has a significant role to play in so much as light. I have some cymbidiums that are growing in full sun and still a deep shade of green and show no signs of burning. I planted out the runts of a flask of Phrag. besseae x boiserianum in the leaf litter under my lychee tree a few months ago, and at the time they go not direct sun. Now, because of the sun rising and setting at a different angle, and longer days they are in direct sun for about 3 hours a day and are doing better. I have a significant amount of constant wind, ranging from 15-25 mph at our house. I believe this is the reason my plants are not burning. So far this summer the highest temperature I have recorded in my greenhouse was 84 degrees. Now I know that is not that high but considering my Den. cuthbertsonii are thriving and blooming I think that air movement has offset temperature in my case.

 

[limuhead]

Another side note, but I have increased my ppm(from about 75 up to 125) on my fertilizer and started using an ammonia based nitrogen. It is my belief that with more sun orchids can utilize more nutrients, specifically nitrogen. I am still using k-lite periodically for the calcium and dolomite as well. Since I have been using Miracle Grow(30-10-10) I have noticed a significant increase of growth, leaves as well as roots. It could be just that it is summer, but I read somewhere that orchids potted in Orchiata seem to do better with ammonia based nitrogen and it seems to be working pretty good.