| Abstract: | Measurements of electrical potential difference (PD) and potassiumactivity were carried out on the intact leaf of Tradescantiavirginiana. PD gradients across the stomatal complex were observedwith both open and closed stomata. The guard cell PD appearedto be linearly related to stomatal aperture. With the stomataopen a gradient of potassium activity across the stomatal complexwas observed which became reversed on stomatal closure. Calculationof the driving forces on potassium suggested that it was distributedpassively between the vacuoles of the cells of the stomatalcomplex. The electrophysiological data obtained from this investigationenabled potassium activity in the apoplast to be calculated.The results showed that on stomatal closure there was a massiveincrease in the potassium activity in the guard cell wall. Key words: Stomata, Ionic gradients, Electrical potentials |
