Charles,
You are probably thinking of cystoliths with in lithocysts. Calcium deposits in the vacuole of certain surface cells of leaves. They are not found in roots that I remember, but that was 35 years ago when I studies this.
At 1:27 AM -0400 4/13/05, Charles Ufford wrote:
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
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