Uptake of inorganic nitrogen by codium fragile subsp. tomentosoides (chlorophyta)1
1978
Hanisak, M Dennis | Harlin, Marilyn M.
The uptake of nitrate, nitrite and ammonium by Codium fragile subsp. tomentosoides (van Goor) Silva was measured at different combinations of temperature (6–30 C) and irradiance (0–140 μEin.m‐². s‐¹). Uptake of all three forms of N was greater at 12–24 C than at 6 and 30 C. Although uptake was stimulated by light, saturation occurred at relatively low irradiance (7–28 μEin m‐² s‐¹, depending on the N source and temperature). The Michaelis‐Menten uptake constants (Vₘₐₓ K)varied with temperature. Vₘₐₓ was greatest at intermediate temperatures and K was lowest at lower temperatures. The Vₘₐₓfor NH₄ ⁺ was higher and the K, for NH₄ ⁺was lower than those for NO₃ ‐ ‐ and NO₂ ‐ ‐. Codium was capable of simultaneously taking up all three forms of inorganic N although the presence of NH₄ ⁺ reduced the uptake of both NO₃ ‐ ‐ and NO₂ ‐ ‐. The results of this study indicate that part of the ecological success of Codium in a N‐limited environment may be due to its N uptake capabilities.
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