Some plants are known to actively close their stomata in the presence of foliar pathogens, inhibiting pathogen entry into leaves, leading to 'stoma-based immunity' as the first line of defense. However, the variation in stoma-based innate immunity across the diversity of vascular plants remains unclear. Here, we investigated the stomatal response and guard cell signaling pathway in various seed plant, fern, and lycophyte species when exposed to the bacterial pathogens or pathogen-associated molecular patterns (PAMPs). We observed active stomatal closure in 10 seed plants when exposed to bacteria or PAMPs, whereas none of the nine fern and one lycophyte species exhibited this response. The PAMP flg22-induced reactive oxygen species burst was observed in all species, but the downstream signaling events, including cytosolic Ca