Figure 3.

Further phenotyping of CPK13-overexpressing plants. A, Expression levels of CPK13, KAT2, and KAT1 genes (normalized with the TUB4 housekeeping gene) relative to wild-type plants (WT) in three independent CPK13-overexpressing lines (OE13#3, OE13#4, and OE13#1). Data (means ± se, n ≥ 15) result from qRT-PCR performed on cDNA extracts from 15-d-old seedlings. B, Stomatal conductance of wild-type and CPK13-overexpressing plants (OE13#3, OE13#4, and OE13#1) over an 8-h-long illuminated period following a 12-h-long darkness period. Data are means ± se (n ≥ 6 plants in three independent experiments). Each individual value represents the leaf conductance assayed with a porometer at time 0 (light onset) and 1, 2, 3, 6, and 8 h after onset (same leaf of a given plant). All measurements were done as blind. C, Stomatal index measured as described by Royer (2001) for the wild type and OE13#3, OE13#4, and OE13#1 lines from epidermal peels featuring approximately 1,000 stomata. Data are means ± se. All measurements were done as blind. D, Mean stomatal apertures measured on epidermal strips peeled from wild-type and CPK13-overexpressing plants. Light-triggered stomatal opening assays were performed on the same plant genotypes as in A (the wild type, OE13#3, OE13#4, and OE13#1). Light onset was at time 0, and average stomatal aperture (400 or more stomata from six or more plants by genotype) were measured at 0, 1, and 3 h. All measurements were done as blind. *P ≤ 0.05, **P ≤ 0.01, and ***P ≤ 0.001 by Student’s t test.