SCV Outdoor Report: Thermostats
By: Wendy Langhans
OK, I admit it: I do not know how to program our thermostat. Oh I can switch it on and off all right. I can even reset the temperature (I think). But I don’t understand that geeky stuff about programing the thermostat to maintain “x” temperature between “y and z” hours. Yet every year, many flowering plants do just that - depend on their internal clock and thermostat to control when to bloom. So just how do they do that?
For many years, botanists have been studying the mechanism by which plants know when (and when not) to produce flowers. In 1936, a Russian scientist introduced the Florigen hypothesis, a hormonal theory of flowering plant development. The hypothesis states that flowering is “activated by a special molecule called Florigen”. It was not until 2005 that the molecular/genetic pathway was identified. Florigen is a type of molecule known as a messenger RNA. (For a technical explanation, click here.)
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But let’s take a step back - what activates this Florigen molecule? Well, we know that many flowers bloom in the Spring. If we think about the environmental changes that occur during Spring, we know that the days grow longer and the nights grow shorter. So that’s a good place to start our search. And sure enough, scientists found that Florigen was activated by an increase in the number of hours of daylight.
Along with the increase in number of hours of daylight, there is also an increase in temperature. Does that have an effect on Florigen too? Recently, researchers at the John Innes Centre in the UK discovered a genetic “switch that accelerates flowering time in response to temperature”. They discovered a gene, known PIF4, that binds to and activates Florigen, but only when the temperature is high enough.
So it seems that, when deciding when to bloom, some flowering plants have their programmable thermostat all figured out. Not only do they know the number of hours of daylight, they also know the temperature. I guess that makes them smarter than me - a lot smarter. Maybe I ought to go back and re-read the instruction manual.
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