A typical change in the proton flux from S. pimpinellifolium leaf tissue induced by 100 nm systemin or by 400 nm systemin after the addition of 100 nm Ala-17. A, 100 nm systemin. B, 400 nm systemin after the addition of 100 nm Ala-17. Continuous line, pH of the unstirred layer at 10 and 50 μm from the cell wall (left y axis). Dotted line, Calculated H⁺ flux based on the pH at 10 and 50 μm (right y axis). A vertical line indicates the moment of addition of the indicated solute. When the flux becomes more positive, this means either an increase of the influx or a reduction of the efflux. Typical experiments of at least three experiments are shown.