The development of the digestive glands and enzymes in the pitchers of three nepenthes species: N. alata, N. tobaica, and N. ventricosa (Nepenthaceae)

The development of digestive glands in pitchers of three species of Nepenthes (N. alata Blanco, N. tobaica Danser, and N. ventricosa Blanco) was studied by LM and SEM, and the presence of digestive enzymes was examined by enzyme cytochemistry. Pitchers at various developmental stages were studied, corresponding to prepitcher inflation, early pitcher inflation, postinflation ( before lid opening), and fully mature open pitcher. Pitchers from all species showed the presence of digestive glands in the pitcher cavity, and each species exhibited a unique gland structure. Digestive glands formed from epidermal cell division, most glands having direct connections with underlying vascular bundles. Enzyme presence was observed in both opened and unopened pitchers for all enzymes assayed and was localized in digestive glands. These results indicate that the genus Nepenthes digestive glands are capable of producing a wide range of digestive enzymes both during and after pitcher development. They are thus functionally carnivorous.