Once the architecture of the primary cell wall has been established
during cell division, the cell wall must still be able to
"loosen" or alter this structural matrix during the process of cell
elongation. The effect of auxin on cell elongation has been well
studied and models involving both obligate new gene expression
and wall acidification have been proposed to explain its action.
It is well established that treatment of plant tissue with auxin
results in the synthesis of new gene products, one of which may
be localized in the cell wall (7). However, the contribution that
this induced gene expression makes to the mechanism of auxin
regulated cell wall elongation has not yet been determined. The
observation that there are two separate elongation responses to
auxin in higher plants, one which may ready the wall for the
process of elongation and a second which requires the action of
newly synthesized gene products, has led to the suggestion that
the distinctly different models of gene expression and wall
acidification initially proposed are not incompatible