“…It was suggested that factors, possibly metabolic, which are controlled by hormones were common to vegetative growth of both host and parasite. Although it was suggested (31) that IAA might modify pathways of metabolism, subsequent work (5) indicated that the low C./C, Extension of these ideas to cereal rusts such as stem rust of wheat is difficult because visual growth disturbances are absent. Certain treatments (17,27,31) which may be related to hormonal changes can cause breakdown in resistance of wheat to rust.…”