In article <1993Feb15.113349.13686 at gserv1.dl.ac.uk> Tony Travis,
ajt at rri.sari.ac.uk writes:
>Is the plant responding to a mechanical stimulus here, or is it eg.
>temperature (from the hands) or damage to the hairs on the surface and
>consequent changes is the thickness of the boundary layer ?
>>Or, is it perhaps a chemical transferred from your green fingers ? ;-)
It is the mechanical stimulus. The most familiar example is probably the
curling of pea tendrils when they contact a support. However, stems are
also quite sensitive. Mark Jaffe and Cary Mitchell have been working
quietly on this for decades. A few years ago Janet Braam was identifying
genes turned on (in Arabidopsis) by spraying various compounds on the
plants. .She found the same genes turning on regardless waht she
sprayed--even water. It turned out to be the same mechanical stimulus.
Both the growth response and the mRNA accumulation are fast--a few