Modulates overall growth by reducing the proliferation activity of meristematic cells and delaying development (PubMed:18359753). Flavonol-specific transcription activator involved in the regulation of several genes of flavonoid biosynthesis. Activates the expression of CHS, CHI, F3H and FLS1 (PubMed:17419845, PubMed:20731781). Confers tolerance to UV-B (PubMed:19895401). Expressed in seedlings, roots, cotyledons, leaves and apical meristems. Expressed in root and shoot meristems and also in young still meristematic leaf and flower primordia (PubMed:18359753). In seedlings, accumulates ubiquitously at low levels. Expressed in shoot apical meristem (SAM), primary leaves, apex of cotyledons, and at the hypocotyl-root transition. In roots, present at the origin of lateral roots and the root tip, as well as in the vascular tissue of lateral roots (PubMed:17419845). Accelerated germination, faster hypocotyl and primary root elongation, more lateral and adventitious roots formation, faster development of the inflorescence, and more lateral inflorescences initiation and fruits (PubMed:18359753). The double mutant myb11 myb111 and triple mutant myb11 myb12 myb111 accumulate less flavonols in roots, leaves, stems, inflorescence, and siliques. The double mutant myb11 myb12 is specifically altered in flavonols content of siliques (PubMed:20731781). The triple mutant myb11 myb12 myb111 is impaired in flavonols biosynthesis and exhibits a reduced UV-B tolerance (PubMed:17419845, PubMed:19895401). Promotes flavonoid biosynthesis when expressed in tobacco (Nicotiana tabacum) through up-regulation of the biosynthetic genes. Extended C-terminus.