Figure 1.

The mkp1 mutant is hypersensitive to UV-B-induced stomatal closure. Leaves of wild-type (WT) Ws, the mkp1 mutant, and line 6 (a representative line of mkp1 mutant complemented by the expression of wild-type MKP1) with open stomata were exposed to different doses of UV-B for 3 h (A) or to 0.5 W m⁻² UV-B for different times (B), then stomatal apertures were measured in epidermal strips from abaxial surfaces of the treated leaves. The data shown are means ± se of at least three independent experiments, each with 50 stomata. Means with different letters are significantly different at P < 0.01.