Fig. 3. Self-supporting and lianescent xylem anatomy. (a ) Stem cross-section showing self-supporting xylem (SS) , characterized by small radially arranged vessels formed only by the fascicular cambium, opposite to protoxylem poles (black arrows), and a high proportion of fibers. The beginning of the lianescent xylem (L) is marked by the concomitant production of several large vessels (white arrows) not restricted to radial files and the reduction of fiber amount. The large vessels are associated with small vessels and comprise a larger proportion of the xylem in this phase. (b ) Longitudinal radial section of the xylem. Ray composition changes from upright cells in SS to mainly square and procumbent cells in L (white arrows). Septate fibers (arrowheads) are found in both phases. Vessel (v). (c ) Self-supporting and lianescent xylem vessel diameter classes distribution. Scale bars: (a) 125 μm; (b) 100 μm.
This analysis highlights the distinct characteristics of self-supporting and lianescent xylem, including the broader distribution of vessels in the later phase, no longer restricted to the fascicular regions. The production of large vessels in the lianescent phase significantly increased water potential specific conductivity and reduced the number of cells per area.
Table 1. Quantitative characterization of self-supporting and lianescent xylem.