Figure 4.

Conceptual diagram of inter-relations of ethylene regulation during nodulation and root growth. Ethylene works through balanced signalling on root and nodule meristems. Additionally the ‘plant immune response’ is activated leading to concomitant biochemical changes such as alterations of the phenylpropanoid pathway. These in turn affect ‘rhizobia’ as well as endogenous plant processes such as hormone translocation. Mutations in the ETR1 receptor gene are complex to analyse as it is unclear what tissue specificity and distribution this receptor has relative to related receptors like ERS1.