Involved in the production of blood-red nectar containing the alkaloid nesocodin and that serves as a visual attractant for pollinator visitation, including vertebrates such as Phelsuma geckos (PubMed:35074876). The nectar is initially acidic and pale yellow, but slowly becomes alkaline before turning into red within 24 hours (PubMed:35074876). Together with NEC2 and NEC3, facilitates the condensation of sinapaldehyde ((E)-3,5-dimethoxy-4-hydroxycinnamaldehyde) and proline to form nesocodin, a pigment with a stable imine bond (PubMed:35074876). Mediates the alkalinization (pH increase) of the flower nectar by catalyzing the reversible hydration of carbon dioxide (PubMed:35074876). H(+) + hydrogencarbonate = CO2 + H2O One-carbon metabolism. Homodimer. Confined to nectaries. Belongs to the alpha-class carbonic anhydrase family.