In 1952, Audus began looking into the action in plant roots of what were then called plant "hormones", and are now known as "growth regulators". This research represented something of a rebirth of the study of the effect of gravity on plants. His book Plant Growth Substances, published in 1953 and expanded in 1959 and again in 1972, was for many years the standard text on that topic. His 1964 book The Biochemistry and Physiology of Herbicides was likewise the standard text on that subject. From 1965 to 1974, Audus served as editor of the Journal of Experimental Botany. His work with plant growth regulators had significant practical consequences in the fields of forestry, agriculture, and horticulture.
