Figure 3.

phyB Is Required for the Systemic Regulation of Stomatal Development

(A) phyB-9 mutants do not respond to shading. Plants were germinated at a photon irradiance of 250 μmol m⁻² s⁻¹, and on emergence of L14, developed leaves were shaded with neutral density filters to a photon irradiance of 50 μmol m⁻² s⁻¹, with L14 exposed to 250 μmol m⁻² s⁻¹ (Sha). Control SI of the equivalent leaf from plants grown 250 μmol m⁻² s⁻¹ are shown for comparison (Con). Mean values are shown with error bars indicating mean ± SEM. Symbols indicate significant difference in SI compared to the control (250); ^∗p < 0.05.

(B) Quantitative gene expression analysis of stomatal developmental genes in Col-0 and phyB-9 mutants following shading. Plants were grown as in (A), and RNA was extracted from L14 at t = 0 and t = 6 hr postshading of mature leaves. Expression is relative to L14 from unshaded plants (Col-0 or phyB-9, respectively) at the equivalent time points. Error bars indicate mean ± SEM from three biological replicates (Student’s t test p values for t = 0 compared with t = 6; SPCH: Col-0 = 0.12, phyB-9 = 0.51; MUTE: Col-0 = 0.02, phyB-9 = 0.89; FAMA: Col-0 = 0.15, phyB-9 = 0.39; STOM: Col-0 = 0.09, phyB-9 = 0.39).

See also Figure S3.