The Rhizobium ? legume symbiosis: observation of root infection by bright-field microscopy after staining with methylene blue

Abstract
Staining of infected legume roots with 0.01% methylene blue facilitated the observation of the initial steps of the Rhizobium—legume symbiosis. It allowed particularly the visualization by bright-field microscopy of infection threads in the root hairs and the root cortex of the host plant.