PREDICTING THE KINETICS OF DISSOLVED INORGANIC CARBON LIMITED GROWTH FROM THE SHORT-TERM KINETICS OF PHOTOSYNTHESIS IN SYNECHOCOCCUS LEOPOLIENSIS (CYANOPHYTA)1 |
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Authors: | David H. Turpin Anthony G. Miller John S. Parslow Ivor R. Elrifi David T. Canvin |
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Abstract: | The blue-green alga (Cyanobacterium) Synechococcus leopoliensis (Racib.) Komarek was grown in dissolved inorganic carbon [DIC]-limited chemostats over the entire range of growth rates. At each growth rate, the kinetics of photosynthesis with respect to [DIC] and the maximal rate of photosynthesis (Pmax) were determined. The half-saturation constant for [DIC]-limited photosynthesis (K1/2DIC) for cells growing below 1.7 d?1 was constant (4.7 μM) whereas for growth rates between 1.7 d?1 and 2.1 d?1 (μmax) the kinetics of photosynthesis were multiphasic with an apparent K1/2DIC between 1.5–2.0 mM. Pmax increased in a linear fashion with growth rate for growth rates below 1.7 d?1. No trend in Pmax was apparent for growth rates greater than 1.7 d?1. These kinetic parameters were used to predict a growth rate versus [DIC] relationship. Results show that the Monod relationship is a physiologically valid expression of growth as a function of [DIC] provided (K1/2DIC) remains constant. The major change in (K1/2DIC) as μ approaches μmax results in the conclusion that two separate and distinct Monod equations must be used to describe growth as a function of DIC over the entire growth range. These results point to a major discontinuity in the μ vs. [DIC] curve at 1.7 d?1 which corresponds to the change from high to low affinity photosynthetic kinetics. We believe these results account for the previously described deficiencies of the Monod equation in describing [DIC]-limited algal growth. |
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Keywords: | bicarbonate Cyanobacterium Cyanophyta growth kinetics Monod equation nutrient limitation photosynthesis photosynthetic kinetics Synechococcus |
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