Ty THE RESIDUAL EFFECT OF AXENiI ON THE CELL WAVLIJ

The present paper concerns the nature of the relationship between auxin and the expansion of the plant cell. It will be shown that it is possible to separate in time the action of auxin on the cell from the act of cellular expansion by water uptake. The separation of auxin action from cell expansion is achieved as follows: auxin is first applied to tissue which is kept from expanding by a suitably high external osmotic concentration. The tissue is then allowed to expand in water under conditions in which the action of auxin is blocked by a suitable inhibitor. An effect of the auxin pretreatment upon the tissue is manifested by an increased expansion of the auxin treated tissue above that of the non-auxin treated control tissue. Experiments of this nature were first performed byA. N. J. Heyn in 1931 (4) and were continued by Thimann (9). Heyn concluded that the action of auxin results in a loosening of the cell wall. In these experiments, however, expansion was not completely suppressed during the period of auxin action. The possibility remains, therefore, that the effects observed may not have been due to the direct action of auxin but rather indirectly due to some auxin-induced elongation. The present experimental procedure permits