<p>The present invention addresses the problem of providing a plant cell differentiation promoter with which it is possible to promote differentiation from a callus to a normal adventitious embryo, or promote differentiation of an adventitious root or adventitious bud from a plant cutting, and as a result, obtain a regenerated plant with stability. The present invention provides a plant differentiation promoter comprising as the active ingredient a specific ketole fatty acid or derivative thereof.</p>
