on 4/13/05 1:04 AM, Mark wrote: > This brings up a question which I may have already answered above > (light), but I don't know for sure. What is the trigger that causes > auxin to know if it is in a root to grow downward with the pull of > gravity? Is is lack of light or the presence of some root cells? Light > causes new growth to grow upward, but does less light with gravitational > pull cause roots to grow downward? With epiphytes root growth maybe > dictated by contact with a surface or otherwise light? > > Mark Sullivan
Hello Mark, I remember a little from plant phys class that some plants (can't say all as I don't know if is the case) have something like crystals or some other solid structure that is inside certain cells. Can't remember if they are free-floating or attached. Where these 'objects' cause pressure on part of the cell insides due to gravity that is 'down', and if the cells are designed to grow down they follow the signal and if they are to go up, they go opposite the pressure in the cell. Hope someone has a better explanation than that! charles -- Charles Ufford Calen the Border Collie CGC - now in Heaven Oriskany, NY USA IPA, Central NY and Southern Tier Orchid Societies [EMAIL PROTECTED] http://www.paphiopedilum.net Http://www.geocities.com/charlesufford _______________________________________________ the OrchidGuide Digest (OGD) orchids@orchidguide.com http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
