Altered cytokinin distribution in the shootless maize mutant ed*41

The distribution of cytokinins is strongly altered in seedlings of the shoo tless ed*41 mutant of maize (Zea mays L.), compared with wild-type. Immunol ocalisation of zeatin and analysis of cytokinin levels clearly indicate tha t these hormones are not present in the shoot apex zone of the mutant. Sinc e an anomalous differentiation of vascular tissues has also been observed i n the mutant, a major role of vascular connection in hormone translocation affecting development of the shoot apical meristem is proposed. Immunolocal isation of zeatin was confined to the root cap, cortex and vascular tissues of both mutant and wild-type seedlings suggesting a tissue-specific synthe sis of this hormone in the root. A time-course of cytokinin distribution in the wild-type developing shoot provided evidence that the tunica and corpu s zones become competent to respond to cytokinins in subsequent periods, ve ry probably in conjunction with photomorphogenesis. On the contrary, this p athway is totally disrupted in the mutant. Taken together, the data point t o a relationship between the ed*41 mutation, inadequate vascular connection and disrupted hormone translocation.