To identify novel regulators of stem cell renewal, we mined an existing but little explored cell type-specific transcriptome dataset for the Arabi-dopsis root. A member of the TGA family of transcription factors, TGA8, was found to be specifically expressed in the quiescent center (QC). Mutation in TGA8 caused a subtle root growth phenotype, suggesting functional re-dundancy with other TGA members. Using a promoter::HGFP transgenic approach, we showed that all TGA factors were expressed in the root, albeit at different levels and with dis-tinct spatial patterns. Mutant analyses revealed that all TGA factors examined contribute to root growth by promoting stem cell renewal, mer-istem activity, and cell elongation. Combining transcriptome analyses, histochemical assays, and physiological tests, we demonstrated that functional redundancy exists among members of clades Ⅱ and V or those in clades I and Ⅲ. These two groups of TGA factors act differently, how-ever, as their mutants responded to oxidative stress differently and quantitative reverse tran-scription polymerase chain reaction assays showed they regulate different sets of genes that are involved in redox homeostasis. Our study has thus uncovered a previously unrecognized broad role and a mechanistic explanation for TGA fac-tors in root growth and development.