Figure 2.

The mkp1 mutant is hypersensitive to UV-B-induced NO production but not to UV-B-induced H₂O₂ production in guard cells. Leaves of wild-type (WT) Ws, the mkp1 mutant, and line 6 (a representative line of mkp1 complemented by the expression of wild-type MKP1) with open stomata were exposed to 0.5 W m⁻² UV-B for the indicated times, then epidermal strips were peeled from abaxial surfaces of the treated leaves and fluorescence images and pixel intensities in guard cells preloaded with 50 µm H₂DCFDA (A and B) or 10 µM DCF-2DA (C and D) were recorded. Data of fluorescence pixel intensities (B and D) are displayed as means ± se of three replicates, each replicate with 20 stomata. Means with different letters are significantly different at P < 0.05. Bars in A and C = 10 μm.