by Leslie Cox; Wednesday, November 12, 2014
thermonasty (thur-MOE-nas-tee): noun – refers to the movement of plant organs in response to changes in temperature
Ever notice how rhododendron leaves droop drastically and curl when the temperatures dip below freezing? This response is a nastic movement allowing the plant to adapt quickly to changes in its environment. Because it is related to temperature, it is specifically called “thermonasty”.
In rhododendrons, the leaves respond to a total of three external stimuli: extreme heat, extreme cold and drought.
In the first two instances, the response is called “thermonasty”, as I have already mentioned. When the leaves droop and curl in response to severe drought conditions, the response is labeled “hydronasty”.
The end result of this drooping and curling is to protect the leaves from membrane damage during extreme stress.