Xylem development in roots of GL-3, MdMYB88, or MdMYB124 overexpression plants and MdMYB88/124 RNAi plants under long-term drought conditions. A, Cross sections of roots from GL-3 and transgenic plants stained with Safranin O. Bars, 100 µm. B, Quantification of root xylem of plants shown in A. Mean Dmax, average length of major axis of vessels; mean Dmin, average length of minor axis of vessels; lumen area, total lumen area, relative to xylem area. n = 10.