Fig. 4. GL2 gene expression and cell organization in the root-hypocotyl junction region of Arabidopsis embryos and seedlings. Brackets in A-E mark the region of the root-hypocotyl junction. Propidium iodide staining (red) was performed with the mature embryo in C and the seedling in D to visualize cell boundaries. (A-D) Root-hypocotyl junction region from torpedo stage embryo (A), curled cotyledon stage embryo (B), mature embryo (C) and 2-day-old seedling (D) bearing the GL2::GFP transgene, viewed by fluorescence microscopy. Note the numerous root hairs (red) visible in D. Bars in A and D, 50 µm; in B, 45 µm; in C, 20 µm. (E) Root-hypocotyl junction region from 2-day-old seedling bearing the GL2::GUS transgene and stained for GUS activity. Numerous root hairs are visible in the junction region. Bar, 50 µm. (F-I) Transverse sections from the root (F), root-hypocotyl junction region (G,H) and hypocotyl (I) from 3-day-old seedlings. Sections were stained with a fluorescent cell wall dye and viewed by fluorescence microscopy. The epidermis (ep), cortex (c), outer cortex (oc), inner cortex (ic), and endodermis (en) layers of the root and hypocotyl sections are indicated. Note the unusual cell anatomy in the ground tissues in G and H, where cells occupying the incomplete middle-ground-tissue layer are indicated by asterisks. Bars in F,G,I, 50 µm; bar in G also applies to H.