Plants can modulate their developmental program depending on environmental conditions, such as nutrient availability and levels and quality of light. A single plant genotype is able to give rise to a wide range of phenotypes. Despite the relevant ecological and evolutionary consequences of this plasticity, very little is known about its molecular basis. A good example of developmental plasticity is the degree of shoot branching. Our knowledge of the control of branching has advanced sufficiently, providing the necessary intellectual framework to investigate more complex properties such as plasticity in the regulatory system. Therefore, the host laboratory examined multiple quantitatively different versions of this regulatory network, which resulted in the identification of Quantitative Trait Loci (QTLs) for branch number and branch number plasticity. In this project, the genes that underlie these QTLs will be identified and characterised. This QTL study may result in the identification of new genes involved in the regulation of shoot branching, but could also reveal allelic variation at known loci. It is possible that these genes affect both branch number and branching plasticity. Alternatively, these genes might be specifically involved in plasticity.