Natural conditions of mineral nutrition are created in laboratories 

 much more easily than natural light field conditions. The only 

 exceptions are the peculiarities of nutrition which depend on light. 

 For example, the rate of absorption of nutients differs under natural 

 conditions and in incubators. In general terms, there is great 

 similarity between the specifics of mineral nutition under laboratory 

 and natural conditions. This is true primarily of nitrogen. 



Under laboratory conditions, the relationship of the concentration 

 of nutrients to the rate of their uptake and growth rate is described by 

 hyperbolic curves, following the Michael is-Menten equation. The 

 constant of this equation represented by the symbol K^ is numerically 

 equal to the concentration of nutrient substances at which the rate of 

 their uptake or of growth of the algae reaches half of its maximum 

 value. The value of K^ for these two processes in cultures of marine 

 diatoms differs slightly. Under natural conditions in the tropics, the 

 relationship between the concentration of chlorophyll is described by S- 

 shaped curves, the right parts of which follow the Michaelis-Menten 

 equation, while the left part is higher, due to underevaluation of 

 ammonia nitrogen (Fig. 9). We can use the right portion of the curve 

 to calculate K^ (Table 3). Comparing the values of K3 for cultures and 

 natural populations, we see that the results produced for AN of natural 

 populations and the absorption of NO3 by small algae agree well. This 

 is understandable, since in both cases the population density is 

 considered in the calculation: K^ in this case represents the rate of 

 processes in each individual cell or pigment unit. K^ for primary 

 production and concentration of chlorophyll reflects the integral effect 

 of the conditions of nitrogen nutrition on the entire phytocenosis. 

 They have the greatest influence on the concentration of chlorophyll, 

 while influencing the level of production somewhat less. 



These data throw additional light on the problem we have already 

 discussed, the mechanism of action of the conditions of mineral 

 nutrition on primary production. The results of determination of the 

 effectiveness of utilization of solar energy in photosynthesis in 

 mesotrophic and eutrophic waters have led to the hypothesis that the 

 primary effect of the conditions of mineral nutrition occurs at the 

 biocenologic level. Analysis of the relationship of AN with the 

 conditions of nutrition, however, has indicated that the conditions of 

 nutrition play a definitive role in the regulation of processes at the 

 level of the organism as well. However, based on a comparison of K^ for 

 AN and chlorophyll (see Table 3), we must conclude that this mechanism, 

 except for regions with very low content of nutrients, is not of great 

 significance for the development of populations of phy topi ank ton. 



No clear relationship has been achieved under natural conditions 

 between temperature and the production characteristics (except for 

 AN). However, the results produced indicate that the effective 

 temperature is manifested at the level of the organism, having no direct 

 effect at the population level. 



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