plant cell wall "loosening"
FSL at psuvm.psu.edu
Wed Mar 30 12:28:53 EST 1994
On 29 Mar 1994 Kate at tamsun.tamu.edu quoted some un-named who wrote:
> From my reading it generally appears that most plant physiologists
> believe the cell walls "loosen" prior to elongating. I have trouble
> with "loosening" as a word to discribe what happens....
The concept of wall "loosening" arises largely from biophysical argument.
It goes as follows: Because growing cells are thin-walled vessels with
turgor pressures of 3-8 atm or so, the walls carry a large tensile
stress, something of the order of 1000 atm static stress. This is only
possible if the wall has great mechanical strength. To make such a
tough, load-bearing network expand in surface area, without rupture, is
not trivial. It is not just a matter of "actively growing", say, by
depositing more material to the wall. Rather, wall stress must first
be reduced by some sort of re-arrangement of the load-bearing wall polymers.
This reduces the cellØs water potential and allows the cell to take up
water, which physically expands the wall. This re-arrangement, leading to
stress relaxation, is what is meant by "loosening". The biochemical
nature of "loosening" (or more correctly, stress relaxation) is another
story - more complicated and still full of debate.
FSL at PSUVM.PSU.EDU
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