Abstract
Carnivorous plants of the genus Nepenthes supplement their nutrient deficiency by capturing arthropods or by mutualistic interactions, through their leaf-evolved biological traps (pitchers). Though there are numerous studies on these traps, mostly on their prey capture mechanisms, the gas composition inside them remains unknown. Here we show that, Nepenthes unopened pitchers are CO(2)-enriched 'cavities', when open they emit CO(2), and the CO(2) gradient around open pitchers acts as a cue attracting preys towards them. CO(2) contents in near mature, unopened Nepenthes pitchers were in the range 2500-5000 ppm. Gas collected from inside open N. khasiana pitchers showed CO(2) at 476.75 ± 59.83 ppm. CO(2)-enriched air-streaming through N. khasiana pitchers (at 619.83 ± 4.53 ppm) attracted (captured) substantially higher number of aerial preys compared to air-streamed pitchers (CO(2) at 412.76 ± 4.51 ppm). High levels of CO(2) dissolved in acidic Nepenthes pitcher fluids were also detected. We demonstrate respiration as the source of elevated CO(2) within Nepenthes pitchers. Most unique features of Nepenthes pitchers, viz., high growth rate, enhanced carbohydrate levels, declined protein levels, low photosynthetic capacity, high respiration rate and evolved stomata, are influenced by the CO(2)-enriched environment within them.