Microbial Activities and Foliar Uptake of Nitrogen in the Epiphytic Bromeliad Vriesea gigantea

• Published in: The New phytologist 2007-07, Vol.175 (2), p.311-320
• Main Authors: Erich Inselsbacher, Camila Aguetoni Cambui, Richter, Andreas, Claus Florian Stange, Helenice Mercier, Wanek, Wolfgang
• Format: Article
• Language: English
• Subjects: 15N uptake; Amino acids; Bromeliaceae - metabolism; Bromeliaceae - microbiology; Epiphytes; Kinetics; Microorganisms; Nitrogen; Nitrogen - metabolism; nitrogen nutrition; nitrogen transformation; Nutrition; Organic foods; Plant Leaves - metabolism; Plant Leaves - microbiology; Plants; Quaternary ammonium compounds; tank bromeliad; Time Factors; vascular epiphyte; Vriesea; Vriesea gigantea; Water tanks
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2007.02098.x

$\bullet$In contrast to terrestrial plants, epiphytic tank bromeliads take up nutrients mainly over their tank leaf surface. The form in which nutrients are available in the tanks is determined by the source and the complex interplay between tank microbes, which transform them and the epiphytes that take them up.$\bullet$To elucidate the importance of different nitrogenous compounds for the nitrogen (N) nutrition of Vriesea gigantea from the Atlantic Rainforest, Brazil, N transformation processes in tank water as well as foliar uptake rates were estimated by15N labelling techniques.$\bullet$Microorganisms actively transformed N compounds in the tank. Specifically, organic N compounds were rapidly mineralized to NH4 +, while nitrification was negligible.$\bullet$Plants took up both organic and inorganic N forms, with a clear preference for$NH_4^{-}$. NH4 +comprised the largest and, because of fast mineralization rates, the most constant dissolved N pool in the tank water. Excretion of ureases by the plants together with an unusual uptake kinetic for urea also suggests that urea may be potentially important as an N source.