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Diurnal cycle and kinetics of ammonium assimilation in the green alga Ulva pertusa


The kinetics of ammonium assimilation was investigated in Ulva pertusa (Chlorophyceae, Ulvales) from northeastern New Zealand. Ammonium assimilation exhibited Michaelis–Menten kinetics with a maximum rate of assimilation (Vmax) of 54 ± 5 μmol g−1 dry weight h−1 and half-saturation constant (Km) of 23 ± 8 μM. In contrast, values for ammonium uptake were considerably higher with a Vmax of 316 ± 59 μmol g−1 dry weight h−1 and Km of 135 ± 46 μM. At environmentally relevant ammonium concentrations (5 μM), assimilation accounted for most (70%) of the ammonium taken up. Darkness decreased the maximum rate of ammonium assimilation by 83%. We investigated the hypothesis that rates of biosynthetic processes are greater in the early part of the day in Ulva. Consistent with this hypothesis, the maximum rate of ammonium assimilation in U. pertusa peaked in the morning and coincided with low levels of the photosynthetic product sucrose, which peaked in the afternoon. There was a diurnal cycle in the rate of ammonium uptake and assimilation in light and dark, but the amplitude was much greater for assimilation than uptake. Moreover, our data suggest that net ammonium assimilation only occurs during the day in U. pertusa. We suggest that two major roles for diurnal cycles are minimisation of interspecific competition for resources and metabolic costs.

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  • Ahn C-Y, Chung A-S, Oh H-M (2002) Diel rhythm of algal phosphate uptake rates in P-limited cyclostats and simulation of its effects on growth and competition. J Phycol 38:695–704

    Article  CAS  Google Scholar 

  • Barr NG, Tijsen RJ, Rees TAV (2004) Contrasting effects of methionine sulfoximine on uptake and assimilation of ammonium in Ulva intestinalis (Chlorophyceae). J Phycol 40:697–704

    Article  CAS  Google Scholar 

  • Berges JA, Montagnes DJS, Hurd CL, Harrison PJ (1994) Fitting ecological and physiological data to rectangular hyperbolae: a comparison of methods using Monte Carlo simulations. Mar Ecol Prog Ser 114:175–183

    Article  Google Scholar 

  • Chow F, de Oliveira MC, Pedersén M (2004) In vitro assay and light regulation of nitrate reductase in red alga Gracilaria chilensis. J Plant Physiol 161:769–776

    Article  CAS  Google Scholar 

  • Conway HL, Harrison PJ, Davis CO (1976) Marine diatoms grown in chemostats under silicate or ammonium limitation. II. Transient response of Skeletonema costatum to single addition of the limiting nutrient. Mar Biol 35:187–199

    Article  CAS  Google Scholar 

  • Coombs J, Hind G, Leegood RC, Tieszen LL, Vonshak A (1985) Analytical techniques. In: Coombs J, Hall DO, Long SP, Scurlock JMO (eds) Techniques in bioproductivity and photosynthesis. Pergamon Press, Oxford, pp 219–228

    Chapter  Google Scholar 

  • Davison IR, Stewart WDP (1984) Studies on nitrate reductase activity in Laminaria digitata (Huds.) Lamour. II. The rôle of nitrate availability in the regulation of enzyme activity. J Exp Mar Biol Ecol 79:65–78

    Article  CAS  Google Scholar 

  • Flores-Moya A, Gómez I, Viñegla B, Altamirano M, Pérez-Rodríguez E, Maestre C, Caballero RM, Figueroa FL (1998) Effects of solar radiation on the endemic Mediterranean red alga Rissoella verruculosa: photosynthetic performance, pigment content and the activities of enzymes related to nutrient uptake. New Phytol 139:673–683

    Article  CAS  Google Scholar 

  • Gao Y, Smith GJ, Alberte RS (1992) Light regulation of nitrate reductase in Ulva fenestrata (Chlorophyceae). I. Influence of light regimes on nitrate reductase activity. Mar Biol 112:691–696

    Article  CAS  Google Scholar 

  • Granbom M, Chow F, Lopes PF, de Oliveira MC, Colepicolo P, de Paula EJ, Pedersén M (2004) Characterisation of nitrate reductase in the marine macroalga Kappaphycus alvarezii (Rhodophyta). Aquat Bot 78:295–305

    Article  CAS  Google Scholar 

  • Harrison PJ, Parslow JS, Conway HL (1989) Determination of nutrient uptake kinetic parameters: a comparison of methods. Mar Ecol Prog Ser 52:301–312

    Article  Google Scholar 

  • Henley WL, Levavasseur G, Franklin LA, Lindley ST, Ramus J, Osmond CB (1991) Diurnal responses of photosynthesis and fluorescence in Ulva rotunda acclimated to sun and shade in outdoor culture. Mar Ecol Prog Ser 75:19–28

    Article  Google Scholar 

  • Koroleff F (1983) Determination of ammonia. In: Grasshoff K, Ehrhardt M, Kremling K (eds) Methods of seawater analysis. Verlag Chemie, Weinheim, pp 150–157

    Google Scholar 

  • Kronfeld-Schor N, Dayan T (2003) Partitioning of time as an ecological resource. Annu Rev Ecol Evol Syst 34:153–181

    Article  Google Scholar 

  • Lartigue J, Sherman TD (2002) Field assays for measuring nitrate reductase activity in Enteromorpha sp. (Chlorophyceae), Ulva sp. (Chlorophyceae), and Gelidium sp. (Rhodophyceae). J Phycol 38:971–982

    Article  CAS  Google Scholar 

  • Levavasseur G, Giraud G (1982) Modification de la photosynthèse nette d’une Ulve de Roscoff en function de la durée d’éclairement. Physiol Vég 20:143–154

    CAS  Google Scholar 

  • Lopes PF, Oliveira MC, Colepicolo P (1997) Diurnal fluctuation of nitrate reductase activity in the marine red alga Gracilaria tenuistipitata (Rhodophyta). J Phycol 33:225–231

    Article  CAS  Google Scholar 

  • Lüning K (1992) Day and night kinetics of growth rate in green, brown and red seaweeds. J Phycol 28:794–803

    Article  Google Scholar 

  • Masclaux-Daubresse C, Valadier M-H, Carrayol E, Reisdorf-Cren M, Hirel B (2002) Diurnal changes in the expression of glutamate dehydrogenase and nitrate reductase are involved in the C/N balance of tobacco source leaves. Plant Cell Environ 25:1451–1462

    Article  CAS  Google Scholar 

  • Mishkind M, Mauzerall D, Beale SI (1979) Diurnal variation in situ of photosynthetic capacity in Ulva is caused by a dark reaction. Plant Physiol 64:896–899

    Article  CAS  Google Scholar 

  • Ramus J, Rosenberg G (1980) Diurnal photosynthetic performance of seaweeds measured under natural conditions. Mar Biol 56:21–28

    Article  CAS  Google Scholar 

  • Rees TAV, Grant CM, Harmens HE, Taylor RB (1998) Measuring rates of ammonium assimilation in marine algae: use of the protonophore carbonyl cyanide m-chlorophenylhydrazone to distinguish between uptake and assimilation. J Phycol 34:264–272

    Article  CAS  Google Scholar 

  • Syrett PJ (1981) Nitrogen metabolism of microalgae. In: Platt T (ed) Physiological bases of phytoplankton ecology. Can Bull Fish Aquat Sci 210:189–209

  • Talbott LD, Zeiger E (1998) The role of sucrose in guard cell osmoregulation. J Exp Bot 49:329–337

    Article  Google Scholar 

  • Taylor MW, Rees TAV (1999) Kinetics of ammonium assimilation in two seaweeds, Enteromorpha spp. (Chlorophyceae) and Osmundaria colensoi (Rhodophyceae). J Phycol 35:740–746

    Article  CAS  Google Scholar 

  • Taylor RB, Peek JTA, Rees TAV (1998) Scaling of ammonium uptake by seaweeds to surface area:volume ratio: geographical variation and the role of uptake by passive diffusion. Mar Ecol Prog Ser 169:143–148

    Article  CAS  Google Scholar 

  • Turpin DH, Bruce D (1990) Regulation of photosynthetic light harvesting by nitrogen assimilation in the green alga Selenastrum minutum. FEBS Lett 263:99–103

    Article  CAS  Google Scholar 

  • Turpin DH, Huppe HC (1994) Integration of carbon and nitrogen metabolism in plant and algal cells. Annu Rev Plant Physiol Plant Mol Biol 45:577–607

    Article  Google Scholar 

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Financial support was provided to T.A.V.R. from the University of Auckland Research Committee. F.G. thank UMR for financial support.

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Correspondence to T. A. V. Rees.

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Communicated by G.F. Humphrey, Sydney.

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Gevaert, F., Barr, N.G. & Rees, T.A.V. Diurnal cycle and kinetics of ammonium assimilation in the green alga Ulva pertusa . Mar Biol 151, 1517–1524 (2007).

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