Foliar Reflectance and Vector Analysis Reveal Nutrient Stress in Prey-Deprived Pitcher Plants (Nepenthes rafflesiana)

Pitcher plants of the genus Nepenthes trap invertebrate prey in pitchers formed from modified leaf tips. This study investigates the benefits of carnivory to Nepenthes rafflesiana, a common Bornean lowland species. Plants were denied prey capture in their natural habitat for 18 wk and were compared with a control group that was allowed to trap, digest, and assimilate prey as usual over the same period. Resource limitation was demonstrated in prey-deprived plants, which produced significantly fewer and smaller pitchers than did control plants. Analysis of foliar spectral reflectance showed increased reflectance within part (608-738 nm) of the photosynthetically active wave band in the prey-deprived plants, signifying a reduction in chlorophyll content. Decreased reflectance at 550 nm in the prey-deprived plants also indicated increased production of anthocyanins, denoting possible nitrogen or phosphorus limitation. Although no difference was found in tissue concentrations of nitrogen or phosphorus between treatments, vector analysis identified a reduction in content of both elements as a result of reduced biomass production in prey-deprived plants. Our findings demonstrate the key role carnivory plays in the nutrition of this species in its natural habitat.