Figure 6.

Alteration of RD20 expression affects ABA sensitivity. A, Germination of seeds of RD20 transgenic lines and their respective controls was scored as emergence of the radicle 4 d after stratification under various concentrations of ABA. B, Postemergence growth was estimated by the percentage of green cotyledons developed in the presence of 1 µm ABA 6 d after stratification. C, Germination of fresh seeds (without stratification) was also accessed in the absence of exogenous ABA. Data are means ± se for three different samples with n > 30 per line per replicate. D and E, Sensitivity to ABA conferred by RD20 depends on the catalytic activity of the encoded enzyme. The germination of seeds containing an empty vector or overexpressing active or catalytically impaired enzyme was scored in the presence of 5 and 10 µm ABA (D). Green cotyledons that developed in the presence of 5 µm ABA were counted 4 d after stratification (E). Data are means ± se of three different biological samples (n > 30 per line per sample). In all parts, differences between transgenic plants versus their respective controls were significant as indicated: *P < 0.05, **P < 0.01.