Moss stomata do not respond to light and CO ₂ concentration but facilitate carbon uptake by sporophytes: a gas exchange, stomatal aperture, and ¹³ C?labelling study

Stomata exert control on fluxes of CO2 and water (H2O) in the majority vascular plants thus are pivotal for planetary carbon H2O. However, mosses, significance possible function sporophytic stomata not well understood, hindering understanding ancestral evolution these key structures land plants. Infrared gas analysis 13CO2 labelling, with supporting data from gravimetry optical scanning electron microscopy, were used to measure assimilation exchange young, green, ± fully expanded capsules 11 moss species a range stomatal numbers, distributions, aperture sizes. Moss sporophytes effectively homoiohydric. In line their open fixed apertures, stomata, contrary those tracheophytes, do respond light concentration. Whereas sporophyte cuticle is highly impermeable gases, predominant sites entry H2O loss sporophytes, closely linked total surface areas. Higher photosynthetic autonomy consequent presence numerous may have been our large, gametophyte-independent at onset plant terrestrialization.