Study: plants found to be sensitive to nighttime temps, bud earlier

From the UNIVERSITY OF CAMBRIDGE and the UHI is felt mostly at night department comes this study which may explain some of the early onsets of budding that has been blamed on global warming. Urban Heat Islands are felt mostly at night, for example in Las Vegas, where nights have warmed far faster than days:



This UHI is due to heat retaining infrastructure increasing.

Plant ‘thermometer’ discovered that triggers springtime budding by measuring night-time heat

An international team of scientists led by the University of Cambridge has discovered the ‘thermometer’ molecule that enables plants to develop according to seasonal temperature changes.

Researchers have revealed that molecules called phytochromes – used by plants to detect light during the day – actually change their function in darkness to become cellular temperature gauges that measure the heat of the night.

The new findings, published today in the journal Science, show that phytochromes control genetic switches in response to temperature as well as light to dictate plant development.

At night, these molecules change states, and the pace at which they change is “directly proportional to temperature” say scientists, who compare phytochromes to mercury in a thermometer. The warmer it is, the faster the molecular change – stimulating plant growth.

Farmers and gardeners have known for hundreds of years how responsive plants are to temperature: warm winters cause many trees and flowers to bud early, something humans have long used to predict weather and harvest times for the coming year.

The latest research pinpoints for the first time the molecular mechanism in plants that reacts to temperature – often triggering the buds of spring we long to see at the end of winter.

With weather and temperatures set to become ever more unpredictable due to climate change, researchers say the discovery that this light-sensing molecule moonlights as the internal thermometer in plant cells could help us breed tougher crops.

“It is estimated that agricultural yields will need to double by 2050, but climate change is a major threat to such targets. Key crops such as wheat and rice are sensitive to high temperatures. Thermal stress reduces crop yields by around 10% for every one degree increase in temperature,” says lead researcher Dr Philip Wigge from Cambridge’s Sainsbury Laboratory.

“Discovering the molecules that allow plants to sense temperature has the potential to accelerate the breeding of crops resilient to thermal stress and climate change.”

In their active state, phytochrome molecules bind themselves to DNA to restrict plant growth. During the day, sunlight activates the molecules, slowing down growth.

If a plant finds itself in shade, phytochromes are quickly inactivated – enabling it to grow faster to find sunlight again. This is how plants compete to escape each other’s shade. “Light driven changes to phytochrome activity occur very fast, in less than a second,” says Wigge.

At night, however, it’s a different story. Instead of a rapid deactivation following sundown, the molecules gradually change from their active to inactive state. This is called “dark reversion”.

“Just as mercury rises in a thermometer, the rate at which phytochromes revert to their inactive state during the night is a direct measure of temperature,” says Wigge.

“The lower the temperature, the slower phytochromes revert to inactivity, so the molecules spend more time in their active, growth-suppressing state. This is why plants are slower to grow in winter.

“Warm temperatures accelerate dark reversion, so that phytochromes rapidly reach an inactive state and detach themselves from DNA – allowing genes to be expressed and plant growth to resume.”

Wigge believes phytochrome thermo-sensing evolved at a later stage, and co-opted the biological network already used for light-based growth during the downtime of night.

Some plants mainly use day-length as an indicator of the season. Other species, such as daffodils, have considerable temperature sensitivity, and can flower months in advance during a warm winter.

In fact, the discovery of the dual role of phytochromes provides the science behind a well-known rhyme long used to predict the coming season: Oak before Ash we’ll have a splash, Ash before Oak we’re in for a soak.

Wigge explains: “Oak trees rely much more on temperature, likely using phytochromes as thermometers to dictate development, whereas Ash trees rely on measuring day length to determine their seasonal timing.

“A warmer spring, and consequently a higher likeliness of a hot summer, will result in Oak leafing before Ash. A cold spring will see the opposite. As the British know only too well, a colder summer is likely to be a rain-soaked one.”

The new findings are the culmination of twelve years of research involving scientists from Germany, Argentina and the US, as well as the Cambridge team. The work was done in a model system, a mustard plant called Arabidopsis, but Wigge says the phytochrome genes necessary for temperature sensing are found in crop plants as well.

“Recent advances in plant genetics now mean that scientists are able to rapidly identify the genes controlling these processes in crop plants, and even alter their activity using precise molecular ‘scalpels’,” adds Wigge.

“Cambridge is uniquely well-positioned to do this kind of research as we have outstanding collaborators nearby who work on more applied aspects of plant biology, and can help us transfer this new knowledge into the field.”


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Sandy In Limousin
October 28, 2016 1:18 am

So basically science has caught up with the empirical knowledge passed on by generations of farmers and gardeners?

Reply to  Sandy In Limousin
October 28, 2016 6:52 am

Science has figured out the way behind the empirical knowledge.

george e. smith
Reply to  MarkW
October 30, 2016 2:16 pm

For immediate publication. Just for the record.
I would not book five minutes in a doorless outhouse from “Hotels. Com”
Got that creeps; get your lousy ad off my screen.

Mark from the Midwest
Reply to  Sandy In Limousin
October 28, 2016 6:56 am

No, it hasn’t, most farmers are way ahead in their knowledge about plant physiology. their income depends on being right, not on getting published.

Reply to  Sandy In Limousin
October 28, 2016 9:37 am

Nice research elucidating this temperature-sensitive pathway but what effect has increasing carbon dioxide having on budding? We know atmospheric CO2 is increasing essentially everywhere whereas true variation in temperature in any location is contentious.

george e. smith
Reply to  Sandy In Limousin
October 28, 2016 2:38 pm

So I looked at that first graph. It never does say what the average Temperature for Las Vegas is.
Do these people even know what the average means ??

Old England
October 28, 2016 1:23 am

Very interesting and borne out by an unwitting ‘experiment’ on the farm this year with London Plane tree seedlings.
I tried to grow these from seed for a couple of years without success and resorted to looking for seedlings around one of our London Plane trees in the late summer last year year. I ended up with about 20 of them and all were potted up. Another seedling appeared in the spring in a pot that my wife, for no particular reason although the leaves are quite attractive, put on the kitchen window sill with 2 of the previous year’s seedlings.
The other 18 year old seedlings were immediately outside the kitchen against a south facing wall in a tray for water. We have a thermometer in the kitchen and another (remote one) on the North side of the house and because we leave the kitchen door open during daylight hours the kitchen air temperature is just slightly lower than the external ambient air temperature (not a great deal of air circulation and the insulation means it is not heated by the sun). the sunlight would have been identical for both those outside and inside.
Within a month, the inside tree seedlings were double the size of those outside. Today the externally grown ones are around 6 – 8 inches tall whilst the ‘kitchen’ three – which were put outside in September – are 13 – 15 inches tall with far more side branches and leaves.
The only conclusion we could come to was that the kicthen stayed warm overnight (kitchen door closed around sunset) and that was significantly promoting their growth.
So very unsurprising that growth and budding takes place much earlier in Urban setting where UHI has such a major effect on night time temperatures. I suspect the same may hold true for birds and mammals beginning to nest or breed earlier in higher night time temperatures.

Old England
Reply to  Old England
October 28, 2016 1:27 am

Whoops ….. should have been more careful with punctuation ” The Other 18 year old seedlings” … should read “the other 18, year-old seedlings, “

Reply to  Old England
October 28, 2016 7:30 am

Yes, comma’s save lives! Let’s eat Grandma versus Let’s eat, Grandma!

george e. smith
Reply to  Old England
October 28, 2016 2:41 pm

So I have a plant that flowers on the night of August 12th. Two flowers max. Sometimes I get four buds, so two more flowers on the 13th (they are dead in the morning)
So what does that mean about my urban heating at night ??

Tom Harley
October 28, 2016 1:49 am

Interesting post, thanks.
There are some species of wattles in the Kimberley that all flower on the same day, the first for the season is before wet season rain, then periodically during the season depending on the amount of rain. However, every flowering also happens together, all on the same day.
I am still wondering what the trigger is. It can’t be rain the first time, or at all, because their is no correlation. They all flower the same day regardless of whether they are irrigated or not. In irrigated and landscaped gardens or out in the bush, it’s still the same day flowering. Night time temperature may be the cause because last night’s minimum here was 28C and they started flowering today, first time for the season.
This curious species has about 6 relatives that follow this flowering regime.

Walt D.
October 28, 2016 1:53 am

blamed on global warming should be
credited to local warming

Reply to  Walt D.
October 28, 2016 7:19 am

Right !
The first question in any claim of some effect of “climate change” is what is the local record .
Often the lack of any local change , or even it being counter to the barely above noise global change puts the lie to the claim .

Reply to  Bob Armstrong
October 28, 2016 9:32 am

Indeed, like politics all climate is local.

george e. smith
Reply to  Bob Armstrong
October 28, 2016 2:43 pm

Well Antarctic climate isn’t local; it’s way down there on the other side of the pizza.

October 28, 2016 1:53 am

Just idle speculation. Las Vegas has grown rapidly over the last couple of decades. More people means more moisture in the air. Could there be an Urban Humidity Effect helping to raise temperatures in the normally low humidity cool desert nights?

Reply to  Kevin Lohse
October 28, 2016 7:17 am

I looked at some data for the 1×1 cell (38N -117 Tonopah Airport) right near LV (36,1N -115,2), and and rel humidity doesn’t get above 44% after 1943. Nightly cooling is up over 31F the last few years, where the average is only 26F. So they have no loss of cooling at all. But it is quite possible UHI (after looking in google maps, can’t find the thermometer, but there isn’t anything there, but it could be attached to one of the buildings), but, here’s the cell I’m looking at.comment image

Reply to  micro6500
October 28, 2016 7:32 am

In recent decades, LV has been paying people to replace lawns with xeriscaping.
Also, most new homes use AC instead of swamp coolers and older homes have been converting to AC.

george e. smith
Reply to  micro6500
October 28, 2016 2:47 pm

Well you can’t tell ANYTHING from that graph, because it is NOT a band limited function (Infinite curvatures) so it is grossly under sampled, and hence nothing can be obtained from it without serious aliasing errors.
Those sorts of graph define the meaning of the term “idiots”.

Reply to  micro6500
October 29, 2016 10:44 am

Make the drive from Tonopah to Las Vegas, then in the same day drive back to Tonopah, and then your definition of “right near” may change.
I don’t think Tonopah airport data can/should correlate/compare with Vegas in any way whatsoever.

Reply to  micro6500
November 8, 2016 8:05 am

This looks like the 40s returned. I am asking the question if todays temps are really any different than 70 years ago during the height of the last PDO/AMO cycle. It’s not clear when you look at raw data there has been any increase which would mean 0 global warming. It’s only when you add in the adjustments of the billions of dollar “adjustments from gods” that we see raw temps rise 0.5C over the 40s.

October 28, 2016 2:43 am

Multiple studies in the UK – which has records going back hundreds of years – confirm that spring flowering dates are getting earlier in association with warming temperatures… (and yes, there is an urban effect: in urban areas it is even earlier, but still there is a trend across all locations).
This is climate change, not UHI.
Sample study:

Reply to  Griff
October 28, 2016 3:20 am

Interestingly, Griff, the RSPB paper shows current flowering as only slightly earlier than in the 1910-34 period, after which there was a colder period with later flowering dates

Reply to  Griff
October 28, 2016 6:40 am

The flowers in the UK are flowering earlier, with urban areas where there is a UHI effect even earlier… which shows its the temps, not solely UHI producing earlier dates.

Reply to  Griff
October 28, 2016 6:55 am

Everybody except you is already aware that for the last 400 years, temperatures have been recovering from the little ice age.

Reply to  MarkW
October 28, 2016 6:55 am

PS: Two hundred years predates the rise in CO2 by well over 100 years.

Tom s
Reply to  Griff
October 28, 2016 6:55 am

And isn’t it just awful? Good grief Griff are you afraid of flowers too?

Reply to  Tom s
October 28, 2016 6:56 am

He seems to be afraid of anything with carbon in it.

Reply to  Griff
October 28, 2016 8:11 am

– which has records going back hundreds of years –

Reply to  Latitude
October 28, 2016 8:48 am

He’s rounding up.

Reply to  Latitude
October 28, 2016 9:12 am


Samuel C Cogar
Reply to  Griff
October 28, 2016 9:26 am

Griff, iffen you, or anyone else, want your Chrysanthemums (sometimes called mums), which are a Fall (September) blooming flower, …… to bloom earlier in the season (late July or August) ….. then all ya gotta do is cover your Chrysanthemums plants with a dark cloth …… a little earlier each day, say 10 minutes, in the late afternoon, to simulate the “shortening” of daylight hours.
That process is called “forcing”, ….. forcing the flower to “bloom” by making it “think” that the Fall season has arrived. The length of “daylight” hours, ….. sunup to sunset, …. more so than near-surface air temperatures, …… controls the lifecycle of hundreds of different plant species.
And ps, iffen one is a “basement” Wacky Tobacca grower/farmer then they know that keeping the “lights” on all day and all night, 24 hours per day, then their marijuana plants grow like “gangbusters”.
And don’t any of you all tell those “researchers” involved in the above noted study about that Wacky Tobacca growing.

John Harmsworth
Reply to  Griff
October 28, 2016 12:58 pm

So Griff,
Those would be the same excellent records that show the long slow climb out of the medieval warm period? And also the steady 2mm rise in sea level since prior to 1900. I thought you felt those records were “unreliable”?

Jay Hope
Reply to  John Harmsworth
October 29, 2016 3:58 pm

Don’t expect any logical answer from Griff. It’s a waste of everyone’s time. He’s a ‘believer’.

george e. smith
Reply to  Griff
October 28, 2016 2:49 pm

By definition (that word urban) UHI is local and therefore is weather not climate.

Clyde Spencer
Reply to  Griff
October 28, 2016 9:13 pm

In a previous WUWT article I plotted the global BEST data and showed that the minimum temperatures were increasing more rapidly than the maximum temperatures. I suspect that the growing seasons are being lengthened by the Spring and Fall killing-frosts being shifted by a few days because of the increase in nighttime temperatures.

Tom Halla
October 28, 2016 2:56 am

1 degree warming causing a 10 percent loss in yield? Considering the geographic range of wheat and rice, that seems rather dubious that the northernmost and coolest areas would have the highest yields.

michael hart
Reply to  Tom Halla
October 28, 2016 3:36 am

Yup. Except when ‘heat stress’ causes plants to bud earlier and have a longer growing season.
It’s a shame that so much good science is contaminated by the need to genuflect before the god of global warming. I understand that they believe it may get them more funding, but it reduces the credibility of the researchers.

D. J. Hawkins
Reply to  Tom Halla
October 28, 2016 7:12 am

My question is this modeled yield reduction or did someone grow something in a controlled environment? Is it 1°C increase in average temperature, max temperature, or minimum temperature?

Reply to  D. J. Hawkins
October 28, 2016 9:42 am

See clarifying comment just posted below. The 10% per Degree C is a very wrong gross oversimplification and exaggeration. But the quite complicated heat stress yield relationships iare observational, not modeled.

Reply to  Tom Halla
October 28, 2016 12:30 pm

And how do the take the UHI effect into the field of agriculture?. To me this is poor science. By going to an UHI in the desert makes it even worse.

Reply to  asybot
October 28, 2016 3:22 pm

Las Vegas may be in the desert, but it still has a UHI.

October 28, 2016 4:17 am

Farmers and gardeners are not planting crops nor harvesting them at earlier dates. Only climate scientists are.harvesting bigger grants at earlier dates.

Reply to  Bill Illis
October 28, 2016 6:44 am

In my part of Flyover country farmers have noticed and are planting earlier. Also not all climate scientist are “mining” grants. Accept the useful science, where ever it comes from, while ignoring the noise.

Pop Piasa
Reply to  Flyoverbob
October 29, 2016 8:36 am

Bob, myself and my Jersey Co. IL neighbors plant whenever conditions permit (soil temp, moisture, weather predictions, soil prep, etc.)
Some years that’s in March, other years it’s May. At 60 years old, I have seen no trend either way.
The southern Peach trees that we planted during the 90’s when we were told the zones had moved northward only fruit in years like 2012, (when we had our earliest crop plantings and our worst harvest in a decade) and almost died during several of the extended sub-zero (F) periods.

October 28, 2016 4:29 am

Thermal stress on crops reduces yield. Since crops are up, not down, perhaps we can get a good definition of just what thermal stress is and is not? Clearly this problem is not impacting crop yields now.

Bruce Cobb
Reply to  hunter
October 28, 2016 5:49 am

“Thermal stress”
Climatist slang for dangerously increased temperatures they “know” are coming.
The stress that Climatists feel due to the fact that temperatures aren’t increasing now, which doesn’t follow their Climatist ideology.

george e. smith
Reply to  Bruce Cobb
October 30, 2016 2:13 pm

Fire is thermal stress. Yes it does affect plants.

Reply to  hunter
October 28, 2016 9:38 am

Hunter, see my just posted comment below for an summary explanation.

Reply to  hunter
October 29, 2016 10:17 am

Without considering what the crop seed vendors are doing to seeds over time there is no way to usefully compare crop yield vs climate.

October 28, 2016 4:42 am

On my kitchen window there is a Christmas “cactus” plant, adjacent to hot water tap and not far from a microwave oven, it is exposed to some day light but also to the florescent and incandescent lighting during mornings and often late into night. It has been there since 1981. None of the instructions (see the link) are followed, it is watered sporadically, and occasionally pruned a bit, and still after all these years it flowers between 10 -15th of December. It can’t believe it is length of the daylight, since often during day hours, window blind is fully down and the plant is in a semi-darkness. I’m truly puzzled.

Steve Fraser
Reply to  vukcevic
October 28, 2016 5:39 am

The pattern from 1938 is very consistent, with year-to-year changes in a +- 2F band.
What were the other metrics, I.e., population, humidity, rainfall?

Reply to  vukcevic
October 28, 2016 5:50 am

We renamed our Christmas Cactus to Holiday Cactus as to not offend any of the Snowflake generation and it immediately started blooming on Festivus. As with you, we are totally puzzled.

Reply to  vukcevic
October 28, 2016 8:51 am

The Christmas Cactus uses the CAM photosynthesis so may be quite different than the plants described above. That process takes in and processes the CO2 during the night so that H2O loss during the day is minimized so may have a different phytochrome response. By the way the authors didn’t “discover(ed) the ‘thermometer’ molecule that enables plants to develop according to seasonal temperature changes”, they discovered its thermosensing role.

Samuel C Cogar
Reply to  vukcevic
October 28, 2016 10:47 am

The “length of the daylight hours” is probably a misnomer iffen one is going to get “picky” with the verbiage being used ……. simply because your Christmas Cactus doesn‘t have a clock or a leaf-watch (plant equivalent of a pocket-watch) for measuring the amount of time (hours n’ minutes) between sunup and sunset. Thus said, then the “length of the daylight hours” actually means, ….. from the “time” or “duration” that the plant detects solar irradiance each morning until the plant can no longer detect solar irradiance in the late afternoon.
And iffen your Christmas Cactus is being “watered sporadically” then you are in effect, simulating the “lack of rain” dry conditions, that along with the reduction in solar irradiance, triggers the plant’s yearly reproduction phase (blooming, pollination & seed production) of its life cycle.
And the pulled window blinds for part of the day, putting your CC plant in semi-darkness, is no different than the frequent daytime semidarkness as a result of cloudy skies. Like I said before, it is not the total hours and minutes that “count”, it’s the “start” and “end” of the daily solar irradiance.
And iffen I got any of the above, …. wrong, ….. then hopefully someone will offer corrections. I’m old n’ tired and CRS is affecting me more as each week passes by.

Tom O
Reply to  vukcevic
October 28, 2016 10:52 am

I got a bigger puzzle for you then. My Mother brought out a Christmas Cactus to me in Arizona from Maine. Like yours, it faithfully bloomed in December with a much better display of flowers the years that Mom visited. Then, sadly, Mom died in February some years back and that Christmas Cactus has faithfully bloomed every February since. And that is no Joke, but the absolute truth. I have no explanation as to why, and am betting no one is going to be able to explain it, either.

george e. smith
Reply to  Tom O
October 28, 2016 2:52 pm

What is Christmas Cactus? Some sort of Holly ??

Reply to  Tom O
October 28, 2016 3:23 pm

It’s a type of cactus that blooms in mid to late December.

Reply to  Tom O
October 28, 2016 6:18 pm

– it’s a rock cactus, with no real spines or thorns, that we cultivate for a decorative winter indoor plant. Originally from Brazil, people think it’s from the desert SW of the US. (Actually, we do have one native here in AZ that blooms around Christmas – but you don’t want it in your yard or house, it’s rather nasty.)

Samuel C Cogar
Reply to  Tom O
October 29, 2016 6:14 am

December CC blooming when in Maine when under mother’s care.
December CC blooming when in Arizona when under mother’s care.
February CC blooming when in Arizona when under Tom O’s care.
State of Maine latitude — 45.2538° N
State of Arizona latitude – 34.0489° N
Tom O, …… Arizona is situated 11.2049° (latitude) south of Maine, ….. which means that the State of Arizona has more daily “hours” of daylight during the winter months, November to March, than does the State of Maine.
But, but, but, …. “Most Christmas cacti now in cultivation are considered to be hybrids of the crab cactus (S. truncata) and S. russelliana. …… (which) is native to Brazil, …. comment image
Oh my, my, …… the months of December and February are both Summertime months in the Southern Hemisphere in the country of Brazil.
So the question is, ….. is the Christmas Cacti’s inherited genes “triggering” a reproduction cycle (blooming) that is based in/on Brazil’s South America’s “summertime”?
I love science, …….. so many question, ……. so few answers.

Reply to  Tom O
October 29, 2016 11:23 am

Hey TomO,
Nice story, thanks. Seems easy to explain, but impossible to prove.
Send me a cutting/start … faith is someting I lack.

Tom s
October 28, 2016 6:51 am

Climate change is a threat? As we’ve seen some warming over the past several decades and higher co2 levels and global crop yields steadily rising. I detest liars.

Reply to  Tom s
October 28, 2016 7:44 am

There are many to detest – Diogenes, according to most, wandered around ancient Greece carrying a lantern and searching for an honest man. You too, I suspect, need do the same!

October 28, 2016 7:51 am

Is there not also a warming trend in rural stations at night time? If so, how is this explained by UHI?

Reply to  DWR54
October 28, 2016 7:53 am


Reply to  Resourceguy
October 28, 2016 9:47 am

This tool plots GHCN station data up to 2014:
You can filter by rural stations and you can select adjusted and unadjusted data. According to that, 10 GHCN stations in Nevada qualify as ‘rural’.
The trend since 1937 in these 10 sites is 0.106 C/dec warming in the adjusted data.
Unadjusted data is available for 9 of these 10 Nevada sites and the warming rate in that since 1937 is even faster, at 0.15 C/dec.

Reply to  Resourceguy
October 28, 2016 9:54 am

Not all rural sites are.

Reply to  DWR54
October 28, 2016 8:49 am

There are a few rural stations that are seeing a night time warming trend. Most aren’t.
The ones that are seeing such a trend are in areas where irrigation has been increasing, which results in increased humidity.

Reply to  MarkW
October 28, 2016 2:08 pm

“There are a few rural stations that are seeing a night time warming trend. Most aren’t.”
What’s your source of evidence for that claim Mark? I’ve checked a load of the rural sites on the tool I linked to earlier and they mostly seem to be in line with the general warming trend.

Reply to  MarkW
October 28, 2016 3:24 pm

Have you corrected for irrigation changes?

Reply to  MarkW
October 28, 2016 4:57 pm

“Have you corrected for irrigation changes?”
Could you post a link to the source that you have to make this claim re irrigation changes please?

October 28, 2016 8:52 am

UHI is still man made that’s why we need mud huts. Lol. Anthropogenic UHI. lol.

October 28, 2016 9:10 am

I suppose Botanists are unaware of the electromagnetic spectrum and that visible light is merely one segment of the spectrum that also includes infra-red frequencies.
“used by plants to detect light during the day – actually change their function in darkness to become cellular temperature gauges that measure the heat of the night.”
I don’t think the function changes at all, they are merely radiation detectors doing the same job.
I suspect that Sunflowers use the same physiological methods to track the sun. Thy do not swivel at all. During the daylight the eastern side (the side tat gets the first sun) grows while the shaded (western side) grows more slowly if any at all. At night the opposite occurs, positioning the head to be tilted towards the rising sun. The entire process repeats itself…until the plant stops growing (at maturity). After growth stops the sunflower is forever left facing easterly.

John F. Hultquist
Reply to  rocketscientist
October 28, 2016 10:31 am

Thy do not swivel at all.
“And yet it moves” [G. G., 1633]
Further reading:

george e. smith
Reply to  rocketscientist
October 28, 2016 2:56 pm

Light by definition IS visible. Light is your eye’s response to certain EM radiations; it is NOT the radiation itself. Most EM radiation does NOT trigger any response in your eye.
I think that the two words Watt and Lumen explain the distinction.

October 28, 2016 9:35 am

Interesting discovery. The PR statement about heat stress and yield needs four very significant qualifications. 1. It is only true above cultivar specific temperature thresholds. 2. It is mainly true only during anthesis. 3. For wheat and maize (corn) it is only true if the heat stress is also associated with water stress (insufficient soil moisture), because otherwise the plants can compensate somewhat through evapotranspiration. That was the fatal flaw in the infamous US maize study misrepresented to Congress by NRDC. See my first ever 2011 guest post here. 4. 10% is a worst case and is very cultivar dependent. For winter wheat the actual loss is about 1% per degree above 22C during anthesis, which occurs in early spring (Faroog et. al. Heat Stress in Wheat, Crit.Revs. Plant Science 30: 1-17 (2011).
Shame that important science gets grossly overstated climate alarm attached to it.

October 28, 2016 9:48 am

Auxin plant hormone causes strigo-lactone synthesis in the roots, which moving upward in the plant influences auxin in buds to stay there. These buds then stay un-differentiated & new shoot branching is inhibited.
Buds are an auxin “source” in relationship to stems that can be a “sink” where auxin might go. For a bud to activate some auxin must 1st move out of the bud & go to a main stem sink.
Initially that movement is auxin flowing via files of cells & when increased auxin transport gets underway a channeling of auxin gradient begins to be established. Canalization is what connects an auxin source to an auxin sink; the auxin PINs (part of auxin transport dynamic) on the meristem polarize to risen auxin.
Cells sense neighbor cells’ auxin % & polarize PINs toward the greater % auxin; the PINs correlate their location using cell micro-tubule network. The dynamic plays out in the manner of a local signal recognition of the % auxin & cells canalize toward the auxin gradient. Cell wall stress results in increased PINs near a cell membrane & this creates a bio-mechanical signal to neighbor cell indicating which cell has the most auxin, so a cell ends up polarizing their PINs to the cell with the most auxin.
As auxin departs the 1st activated bud enroute to the main stem the potential capacity of the “sink” gets less. Therefore, other buds don’t channel their auxin to that stem “sink” even though other buds have auxin in their stem cells (shoot apical meri-stem). This is why usually only 1 shoot branches in 1 site & plant architecture (layout) takes shape.
When see shoots from buds right on top of one another this is due to a very low % of auxin in relationship to cytokinin plant hormone. Aerial part “stem” cells have auxin to maintain the shoot apical meri-stem in synergy with cytokinin. Increased cytokinin
leads to more stem cells in the meri-stem (conversely, less cytokinin means smaller size shoot apical meri-stem & less activity there).
There are 2 kinds of cytokinin (aromatic & iso-prenoid) & both derived from adenine.
Cytokinin is involved in source-sink relationship, shoot branching, vasculature change, nitrient aquisition, leaf expansion, crop productivity & circadian rhythm – among other things. Original post seems to be detailing a signal mechanism that leads to plant hormone shift, so that cytokinin rises in relation to auxin.
I wonder if the original post effect is due to change induced to sensitivity of the “KNOX” family transcriptor KNAT1. In some plants the pheno-type of shoot forming is linked to cytokinin’s effect on KNAT1. Both the % of cytokinin & altering cytokinin signalling affect the mRNA levels of KNAT1. To get a leaf initiated on bud shoot cytokinin has to rise & exert a regulatory effdct on KNAT1.
Plant tissue expansion coming from zones of dividing cells is found when the % of cytokinin increases. Elevated cytokinin causes increased cell membrane associated calcium where cells are differentiating into buds. Cytokinin exerts cell cycle control since it is needed for cells moving out of the phase which required auxin in order to cycle from G1 to S phase & G2/M transition for eventual cell mitosis.
Incidentally, when de-bud or cut off a growing shoot this results in more cytokinin. Pruning plays out well for most plants’ growth with enhanced vigor because of the combined removal of auxin source (bud or tip “apical” auxin) & cytokinin increase.

John F. Hultquist
October 28, 2016 10:10 am

It would be nice if the writer(s) were neutral on the subject of CAGW and less linear in their thinking. If this article was on paper as a student’s essay, I would have red marks and questions all over it.
Example: “It is estimated that agricultural yields will need to double by 2050, but climate change is a major threat to such targets.
This has nothing to do with the research being described, so it ought not be there. One can also (accepting that it is there) question such things as the word “yields.” And, of course, ask why? Further, corn is grown from Alberta to Alabama and, wonder of wonders, in Mexico. If the growing season gets a bit better, the farmers in Saskatchewan and Alberta could plant more and get higher yields.
Anyway, interesting research. Presentation is convoluted.

October 28, 2016 10:17 am


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