Figure 5.

Effect of Time of Day on Guard Cell Starch Metabolism and Stomatal Kinetics.

(A) Guard cell starch dynamics in dark-adapted (30 min) plants in response to 2-h L, 3-h D, 2-h L, and 2-h D (L, light; D, darkness). Plants were illuminated with 150 μmol m⁻² s⁻¹ white light. Each value represents mean ± se of three biological replicates of >110 individual guard cells obtained from three independent experiments. Different letters indicate statistically significant differences among time points for the given genotype for P < 0.05 determined by one-way ANOVA with post hoc Tukey’s test. WT, wild type.

(B) Normalized whole-plant recordings of changes in g_s–g_initial in plants exposed to the same light regime as given in (A). The g_s values were normalized to values at the EoN, n = 3; values presented are means ± se.

(C) Changes in g_s–g_initial in response to a shift from dark to light in wild-type plants. Data are replotted from (B).

(D) and (E) Rapidity of the stomatal response estimated using a time constant (τ [D]) and the maximum slope of g_s increase (Sl_max [E]) during the two consecutive pulses of light in the wild type. Unpaired Student’s t test determined statistical significance between the indicated comparisons (*P < 0.05; n.s., not significant).

(F) Normalized whole-plant recordings of A-A_initial values from plants under the same light regime as given in (A). Values for A were normalized to values at the EoN, n = 3; values presented are means ± se.