Physiologic responses to Gibberellic Acid (GA), 1-Naphthalene Acetic Acid (NAA), Benzylaminopurine (BAP), and Abscisic Acid (ABA), suggest that Closterium moniliferum has the ability to utilize these plant growth factors. The growth promoters NAA and GA both increased growth when added to the media. The cell division regulator BAP (a synthetic cytokinin). also had a promotive effect on growth. Abscisic acid was found to be inhibitive to growth.