Trap gland morphology and its systematic implications in Taiwan Utricularia (Lentibulariaceae)

The highly specialized trap glands of carnivorous plant are responsible for the digestion and absorption of the prey; however, there are few studies on their systematics and evolution. In this study, the gland morphology of six carnivorous plant species of the genus Utricularia (Lentibulariaceae) in Taiwan, including U. aurea Lour., U. australis R. Br., U. bifida L., U. caerulea L., U. gibba L. and U. striatula Sm., was examined with a scanning electron microscope. The glands on both the outer and inner surfaces of the traps were examined. We found that the external glands had little diagnostic value, but the internal glands could be used in the identification of Taiwan species. Evolutionary trends of gland characteristics are discussed, analyzing morphology of the internal glands, based on previous work. A new hypothesis for the evolution of internal gland structure in Utricularia is also proposed.