Figure 3

I _K,in and I _K,out of wild-type (A), nia1nia2 (B), and QC3 (C) mutant Arabidopsis guard cells following pretreatment with opening buffer (OB). (A) Steady-state current–voltage curves for I_K,in and I_K,out from one guard cell of wild-type Arabidopsis recorded at intervals over 30 min after 2-h OB pretreatment. Shown are data for voltage clamp scans taken at 10 (closed circles), 20 (open circles), and 30 min (closed triangles) after impalement. Clamp scans were from a holding voltage of −100 mV with tail steps to −100 mV. Test voltage steps were to voltages between −80 and +50 mV for I_K,out and to voltages between −100 and −240 mV for I_K,in. Current–voltage curves were fitted jointly to a Boltzmann function (solid lines) and yielding values for g_max of 3.8 and 6.3 μS cm^-2, V_1/2, of −181 and +1 mV, and δ of 1.9 and 1.8 for I_K,in and I_K,out, respectively. Insets: Current traces for time points at 30 min. Scale: 500 μA cm^-2 vertical, 2 s horizontal. (B) Steady-state current–voltage curves for I_K,in and I_K,out from one guard cell of nia1nia2 mutant Arabidopsis recorded at intervals over 30 min after 2-h OB pretreatment. Shown are data for voltage clamp scans taken at 10 (closed circles), 20 (open circles), and 30 min (closed triangles) after impalement. Clamp voltage scans as above. Current–voltage curves were fitted jointly to a Boltzmann function (solid lines) and yielding values for g_max of 0.9 and 6.1 μS cm^-2, V_1/2, of −178 and +5 mV, and δ, of 1.8 and 1.8 for I_K,in and I_K,out, respectively. (C) Steady-state current–voltage curves for I_K,in and I_K,out from one guard cell of nia1nia2 mutant Arabidopsis recorded at intervals over 60 min after 2-h OB pretreatment. Shown are data for voltage clamp scans taken at 10 (closed circles), 20 (open circles), and 30 (closed triangles) 40 (open triangles), 50 (closed squares) and 60 (open squares) min after impalement. Clamp voltage scans as above. Current–voltage curves were fitted jointly to a Boltzmann function (solid lines) and yielding values for g_max of 4.1 and 4.6 μS cm^-2, V_1/2, -182 and −7 mV, and δ, of 1.7 and 1.9 for I_K,in and I_K,out, respectively. NOTE: Data analysis and curve fittings were carried out using SigmaPlot 11 (Systat Software, Inc., USA) and are reported, where appropriate, as means ± SE of n observations. Where appropriate significance was determined using Students’ T-test. Gating characteristics for I _K,in and I _K,out were determined by fitting steady-state current–voltage curves to Eqn.(1)using non-linear, least-squares minimisation and the Marquardt-Levenberg algorithm[39].