Figure 2: How can transpiration, which requires differentiated xylem, deliver sufficient Ca2+ to sustain meristematic growth? Longitudinal section of Nicotiana benthamiana stained with DAPI (blue) to detect DNA and hybridized to fluorescent oligos complementary to tomato golden mosaic virus DNA (pink, short arrows). Viral DNA is transported through phloem and makes a nice marker for developing vascular tissue. Image was visualized with a triple-fluorescence cube for DAPI, FITC, and Texas Red. Orange and green colors are the result of autofluorescence. Most of the cells in this section are undifferentiated. Long arrow points to a tracheary element that has differentiated, but most of the leaf is still developing (section through this leaf is oblique). Bar = 50 microns.