Thermonasty of young main stems of Phryma leptostachya (Phrymaceae).

Thermonasty-like responses were observed on some main stems of Phryma leptostachya (Phrymaceae) plants cultivated in the open. To confirm the thermonastic nature of these responses, the plants were moved into an artificially illuminated chamber and observed under controlled conditions. At low temperatures (about 12 degrees C) and in the dark, slanted terrestrial young main stems of P. leptostachya became prostrate. At higher temperatures (about 25 degrees C) and in the dark, the prostrate stems became slanted. Their movement was confirmed under controlled conditions and is therefore considered to be thermonastic in nature.