Xylem of rattans: vessel dimensions in climbing palms

We examined 11 species in four genera of rattans (Calamus, Daemonorops, Korthalsia, Plectocomia) growing in their native rainforest habitat in Singapore. Using aqueous safranin dye, we found that >95% of all vascular bundles at the base of a mature stem were functioning to transport water. We determined the frequency of vessel lengths in the long stems of these climbing palms by infiltration with dilute latex paint. Separate length distributions were made for metaxylem and protoxylem vessels; in both, there were many short and a few long vessels. The longest protoxylem vessels ranged from 7.5 to 62 cm in length, but one stem had an exceptional protoxylem vessel measuring 3.0 m. Maximum metaxylem vessel diameters were positively correlated to maximum vessel lengths in these species. The longest metaxylem vessel was found in K. rigida and was 3.96 m in length and was constructed from ∼1200 vessel elements (cells). The widest vessel in that same stem was 532 μm in diameter. Long, wide vessels decrease resistance and increase water transport efficiency. In addition, we suggest that wide metaxylem vessels may have an important function in water storage.