Investigation of 67 gymnosperm and angiosperm species belonging to 25 orders shows that epistomatal mucilage plugs are a widespread phenomenon.
Measurements of the leaf water status by using the leaf patch clamp pressure technique suggest that the mucilage plugs are involved in moisture uptake and buffering leaf cells against complete turgor pressure loss at low humidity.
image of an ”Arabidopsis” stomate showing two guard cells exhibiting green fluorescent protein and native chloroplast (red) fluorescence. |Source=”Protein Kinases and Plant Pores.” Gross L, PLoS Biology Vol. 4/10/20