Auxin enhances cell elongation in all of these ways except

acid induced denaturation of cell wall proteins.

Explanation:

Auxins by their physiological activity, resemble indole-3-acetic acid. Its main function is to induce cell lengthening of plants.

In general, auxins can act in other processes, in addition to cell elongation, although this is considered decisive. They are characterized by having an unsaturated cyclic nucleus or derived from such acids.

acid-induced denaturation of cell wall proteins.

Explanation:

Auxins are very strong hormones which are produced by plants naturally. They are mostly found in shoot and root tips where they promote cell division, stem growth and root growth. They affect the plant orientation on the one-sided region by promoting or allowing cell division in response to sunlight.

During the extremely hot conditions, the proteins in the cell wall get denatured or destroyed. Denaturation of protein would result in the death of the cell, which is not the functioning of the auxins. Hence, acid-induced denaturation of cell wall protein is one such exceptional function of auxin.