Anatomy and Mechanical and Hydraulic Needs of Woody Climbers Contrasted with Subshrubs on the Island of Cyprus

Climbers and self-supporting woody plants have different constraints on their stems. Although plants of both growth forms need wood that functions mechanically and hydraulically, climbers have a lower need for mechanical self-support and an elevated need for hydraulic conductance to enable longer-distance water transport. We sampled all the woody climbers (10 species) and most of the woody subshrubs (25 species) of the island of Cyprus, which lies in the easternmost side of the Mediterranean Sea, to characterize their vessel and fiber anatomies relative to mechanical and hydraulic function. Consistent with their lower need for self-support, on average the climbers had lower wood density than did the subshrubs (0.44 g/cm3 ± 0.15 vs. 0.59 g/cm3 ± 0.20, means ± s.d.) and had a lower proportion of their cross-section devoted to fibers (29% ±11 vs. 49% ± 15). Consistent with climbers’ need for higher hydraulic conductance and total plant height, climbers had vessel sizes and frequencies closer to the theoretical packing limit than did subshrubs. Lastly, we grouped species within a growth form by site water availability (dry vs. wet site), site temperature (cold vs. hot site), site water equability (low vs. high), and xylem ring-porosity (ring-porous, semi-ring-porous or diffuse-porous). We then asked whether vessel lumen diameters or vessel frequencies varied by these groupings for the growth forms. Climbers had different vessel lumen diameters or vessel frequencies for six of these eight groupings, whereas subshrubs showed no such differences, illustrating the wide variation in climber wood structure compared to the relatively conservative anatomy of the subshrubs.