Positively regulates stomatal density and patterning. Acts by competing with EPF2 (AC Q8LC53) for the same receptors, ERECTA (AC Q42371) and TMM (AC Q9SSD1). Not cleaved by the protease CRSP (AC Q9LNU1) (PubMed:25043023). Interacts with ERECTA and TMM. Expressed in immature organs, including leaves, stems and flower buds, but not in roots, shoot apical meristem and petals. Detected in the mesophyll tissues but not in the epidermal tissues where stomata develop. The loop (82-95) connecting the two anti-parallel beta-strands (76-81 and 96-101) confers the function to the peptide. Reduced stomatal densities in various organs. Belongs to the plant cysteine rich small secretory peptide family. Epidermal patterning factor subfamily.