Figure 5.

ABA signaling in the root tip: response specificity toward ABA. Seedlings containing the pRD29B::GUS expression cassette were either nontreated or exposed to 30 μm ABA (ABA) or their roots were water stressed (stress; Ψ = −1.0 MPa) for 24 h prior to histological staining for reporter activity. The analysis included seedlings with wild-type ABA response (wt), ABA deficiency, and ABA insensitivity provided by the aba2 and abi1 mutant background, respectively. The pictures arranged in a vertical row represent photographs of the same specimen with one specific treatment, while the horizontal rows represent photographs of the same organ or organ parts of seedlings treated differently. The first horizontal row (A–E) shows a close-up view of the cotyledon (scale bars represent 100 μm), the second the shoot (scale bars represent 1 mm), the third a section of the root (scale bars represent 100 μm), and the fourth the root tip (scale bars represent 100 μm). The specimens were stained for identical periods (1 h) to visualize reporter activity, with the exception of Figure 5, K, N, and O, which were stained for 3 h.