
ALT A multipanel figure showing that unlike angiosperm stomata, fern stomata are insensitive to abscisic acid (ABA), and fern guard cell SLOW ANION CHANNEL (SLAC) homologues are not activated by ABA-signalling kinases. (a) Fluorescent images of guard cells of the angiosperm Nicotiana tabacum (tobacco) and fern Polypodium vulgare after current ejection of 1 mM Lucifer Yellow, or 1 mM LY with 1 mM ABA. (b) Brightfield images of the same guard cells up to 20 min after current ejection. (c) Normalised stomatal aperture over 20 mins, showing a decrease in stomatal aperture in response to ABA in N. tabacum but not P. vulgare. (d) Mean whole-oocyte current measurements of SLAC homologues from the angiosperm Arabidopsis thaliana (responsive) and the ferns P. vulgare and Ceratopteris richardii (not responsive), co-expressed with or without ABA-signalling kinases in Xenopus oocytes.











































