@article {ISI:000339809600009, title = {Dinitrogen fixation associated with shoots of aquatic carnivorous plants: is it ecologically important?}, howpublished = {ANNALS OF BOTANY}, volume = {114}, number = {1}, year = {2014}, month = {JUL}, pages = {125-133}, publisher = {OXFORD UNIV PRESS}, type = {Article}, address = {GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND}, abstract = {Rootless carnivorous plants of the genus Utricularia are important components of many standing waters worldwide, as well as suitable model organisms for studying plant-microbe interactions. In this study, an investigation was made of the importance of microbial dinitrogen (N-2) fixation in the N acquisition of four aquatic Utricularia species and another aquatic carnivorous plant, Aldrovanda vesiculosa. 16S rRNA amplicon sequencing was used to assess the presence of micro-organisms with known ability to fix N-2. Next-generation sequencing provided information on the expression of N-2 fixation-associated genes. N-2 fixation rates were measured following N-15(2)-labelling and were used to calculate the plant assimilation rate of microbially fixed N-2. Utricularia traps were confirmed as primary sites of N-2 fixation, with up to 16 \% of the plant-associated microbial community consisting of bacteria capable of fixing N-2. Of these, rhizobia were the most abundant group. Nitrogen fixation rates increased with increasing shoot age, but never exceeded 1 center dot 3 mu mol N g(-1) d. mass d(-1). Plant assimilation rates of fixed N-2 were detectable and significant, but this fraction formed less than 1 \% of daily plant N gain. Although trap fluid provides conditions favourable for microbial N-2 fixation, levels of nif gene transcription comprised < 0 center dot 01 \% of the total prokaryotic transcripts. It is hypothesized that the reason for limited N-2 fixation in aquatic Utricularia, despite the large potential capacity, is the high concentration of NH4-N (2 center dot 0-4 center dot 3 mg L-1) in the trap fluid. Resulting from fast turnover of organic detritus, it probably inhibits N-2 fixation in most of the microorganisms present. Nitrogen fixation is not expected to contribute significantly to N nutrition of aquatic carnivorous plants under their typical growth conditions; however, on an annual basis the plant-microbe system can supply nitrogen in the order of hundreds of mg m(-2) into the nutrient-limited littoral zone, where it may thus represent an important N source.}, keywords = {Aldrovanda vesiculosa, aquatic carnivorous plants, australis, daily nitrogen gain, intermedia, N nutrition, N-15(2) labelling, nitrogen fixation, Periphyton, reflexa, traps, U, Utricularia vulgaris}, issn = {0305-7364}, doi = {10.1093/aob/mcu067}, author = {Dagmara Sirova and Jiri Santrucek and Lubomir Adamec and Ji{\v r}{\'\i} B{\'a}rta and J Borovec and Pech, Jiri and Sarah M. Owens and Schaeufele, Rudi and Helena {\v S}torchov{\'a} and Jaroslav Vrba} }