FIGURE 4.

Stomatal size but not density significantly changes the speed of stomatal closure. Stomatal conductance (g_s) responses to light-dark-light treatment over 20 min for (A) stomatal size mutants: small size (SS), large size (LS), and control (C). (B) Equivalent g_s response for stomatal density mutants: low density (LD), high density (HD), and C. Note, HD plants also have increased abaxial stomatal size relative to C, SS, and LD. Stomatal closure was instigated by 10 min of complete darkness (0 m^–2 s^–1 PAR) following “steady-state” conditions of saturating light (2,000 m^–2 s^–1 PAR). To re-open stomata saturating light was re-introduced. (C–F) Rate of Δ g_s per minute of stomatal size mutants analyzed in 5-min segments during (C) initial stomatal closure, (D) late stomatal closure, (E) initial stomatal opening, and (F) late stomatal opening. (G–J) Equivalent rate of Δ g_s per minute of stomatal density mutants during (G) initial stomatal closure, (H) late stomatal closure, (I) initial stomatal opening and (J) late stomatal opening. For graphs a and b error bars = S.E.M. For (C–J), boxes indicate the upper (75%) and lower (25%) quartiles and horizontal lines within boxes indicate the median. Whiskers indicate the ranges of the minimum and maximum values, and different letters with a graph indicate a significant difference between the means to at least p < 0.05 (ANOVA, post hoc multiple comparisons, Holm-Sidak method). n = 4–5 plants.