IIRC, Darwin wrote on this topic which fascinated him.
PvR

"monique" schreef
Genetics--Twining direction varies by group. Some plants or plant
families are all left-handers (counter-clockwise) and some are all
right-handers (clockwise).

This was the subject of the famous song "Misalliance" by Flanders and
Swann. http://www.nomorelyrics.net/song/179729.html

M. Reed.



Stan wrote:
Hi there...

Anyone know how or what mechanisim a tendril uses to know which way to
wind around a (wrot iron) support (post)?