Amino acid uptake and profile in bromeliads with different habits cultivated in vitro

Bromeliads can have terrestrial and epiphytic habits. Therefore, they have developed probably different mechanisms for the uptake of nutrients from distinct sources such as the pedosphere and the atmosphere. Many bromeliads, such as the epiphytes, absorb water and nutrients almost exclusively via their foliar trichomes. In contrast, terrestrial bromeliads essentially use their roots to withdraw the nutrients from the soil. The aim of this study was to compare nitrogen (N) nutrition between a terrestrial, Ananas comosus (L.) Merr., and an epiphytic, Vriesea gigantea Gaudich., bromeliad. The in vitro absorption of [3H]glycine and [3H]glutamine was investigated. Plants were also grown in vitro with NH4+, glutamine (Gln) or glycine (Gly) as N sources, and the amino acid profile was analyzed. Ammonium treatment had little effect upon the A. comosus amino acid profile, while asparagine was the main amino acid accumulated in V. gigantea after 3 d in a medium with this nitrogen source. This suggests that V. gigantea accumulate N in compounds with high N/C ratio, allowing it to store higher N level when it is available in epiphytic environment. The two species were able to take up amino acids in vitro, although V. gigantea had a higher rate of amino acid uptake than the terrestrial bromeliad, A. comosus. For both species, Gly was taken up in a higher rate than Gln. The data support the idea that V. gigantea has a luxury consumption when inorganic and organic N are available in the environment, which does not happen in the case of the terrestrial bromeliad A. comosus. It has a more stable source of nutrients, the soil. We can also suggest that amino acids such as Gly, Gln and others present in the bromeliad tank water may be important N sources for V. gigantea and other epiphytic bromeliads in natural habitats.