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COMPARATIVE KINETIC STUDIES OF NITRATE‐LIMITED GROWTH AND NITRATE UPTAKE IN PHYTOPLANKTON IN CONTINUOUS CULTURE 1
Author(s) -
Gotham Ivan J.,
Rhee GYull
Publication year - 1981
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.1981.tb00856.x
Subject(s) - nitrate , biology , chemostat , phytoplankton , growth rate , nitrogen , inverse , nutrient , ecology , physics , mathematics , genetics , geometry , quantum mechanics , bacteria
A comparative study of nitrate‐limited growth and nitrate uptake was carried out in chemostat cultures of Ankistrodesmus falcatus (Corda) Ralfs., Asterionella formosa Hass., and Fragilaria crotonensis Kit. In each species growth rate (μ) was related to total cell nitrogen or cell quota (q) by the empirical Droop growth function. Nitrate uptake was a function of both external N concentration and q. The apparent maximum uptake rate (V m ') at a given μ was inversely related to q – q 0 , where q 0 is the minimum quota. The apparent half‐saturation constant for uptake, (K m ') appears to show a slight inverse trend with μ, although statistical analysis shows that this trend is inconclusive. When q approaches q 0 , V m ' is several orders of magnitude greater than μq, the calculated steady‐state uptake rate. As q increases, however, the difference between these two variables decreases sharply until q approaches q m , the cell quota for nitrogen‐rich cells. At this point the difference between μq and V m ' disappears. This behavior is explained by the feedback regulation of N uptake. The inverse relationship between V m ' and q – q 0 can be described by an empirical three‐parameter equation.