Abstract

ANDRADE R, Charity E et al. Comparative assessment of Lemna obscura growth with organic and inorganic nitrogen sources as a function of pH. Rev. Téc. Ing. Univ. Zulia [online]. 2013, vol.36, n.2, pp.143-152. ISSN 0254-0770.

Discharges of untreated wastewater to water bodies, make them suitable culture media for the overgrowth of floating aquatic plants causing environmental and health problems. Growth of Lemna obscura from the Lake of Maracaibo, Venezuela, in function of the nitrogen sources (NH₄Cl, NaNO₃, CO(NH₂) and NH₄NO₃) at 1 mM and pH (3.5, 4, 5, 6, 7 and 9) was evaluated. Also, the effect of urea (0.1, 1, 5 y 10 mM) at pH 5 was assessed. L. obscura grew between pH of 4-9 in all nitrogen sources. However, at pH 3,5 there was a lethal effect during the first 15 days. The highest growth was achieved at pH 5, and the highest values with urea (1839,67±75,45 fronds). In presence of urea as the best nitrogen source, maximum growth was achieved (2923,00±130,8 fronds) at 1 mM. The effective growth of L. obscura with all nitrogen sources and in a wide range of pH demonstrated the high reproductive capacity and adaptability of this macrophyte, distinguishing their ability to become an aquatic weed in eutrophic water bodies.

Keywords : Lemna; growth; Lake of Maracaibo; nitrogen sources; pH.

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