RESUMO
Since its development in the mid-1980s, microprojectile bombardment has been widely employed as a method for direct gene transfer into a wide range of plants, including the previously difficult-to-transform monocotyledonous species. Although the numerous instruments available for microprojectile-mediated gene delivery and their applications have been widely discussed, less attention has been paid to the critical factors which affect the efficiency of this method of gene delivery. In this review we do not wish to describe the array of devices used for microprojectile delivery or their uses which have already been definitively described, but instead wish to report on research developments investigating the factors which affect microprojectile-mediated transformation of plants.