Stomatal Movements Associated With Potassium Fluxes

Association of potassium ions with stomatal movements is reported here for 22 different plants. These include Ophioglossum engelmanni, Ginkgo biloba , and Pinus sylvestris. In all 22 plants potassium migrates into the guard cells when stomata open in response to light. In addition, potassium migration into guard cells also occurs with night opening in Crassula argentea and with rhythmic opening in Mimosa pudica. Potassium inside the guard or subsidiary cells, conventionally detected through light microscopic observations of epidermal peels treated with sodium cobaltinitrite reagent, may also be mapped by x‐ray microanalysis of such histochemically treated peels, as was the case in this study. In addition to the potassium migration, we also show the movement of chloride as an accompanying anion in Ophioglossum engelmanni, Ginkgo biloba, Plantago rugelii, Begonia sp., and Avena sativa. Eight plants are shown to accumulate potassium inside the stomatal initials or cells of immature stomatal apparatuses; ordinary, immature epidermal cells do not show such an accumulation of potassium. A list in the discussion indicates all the plants in which potassium fluxes associated with stomatal movements have so far been established, including the new examples reported in this paper.