Plant growth regulator (PGR) compositions include a plant growth regulating effective mixture of (A) a N,N-dimethyl piperidinium salt (preferably, mepiquat chloride), (B) a hexitol (preferably, myo-inositol), and optionally (C) a compound which. promotes cytokinesis in plant cells (i.e., a cytokinin). The hexitol and cytokinin are most preferably provided collectively in the composition by the presence of an effective amount of coconut milk. Synergistic results in terms of enhanced cotton lint yields are obtained by applying the PGR compositions of this invention to growing cotton plants.