C02 Concentration 



For many years, it has been common practice to bubble 

 C02 - enriched air through algae cultures. For unicellular 

 green algae, 5% C0 2 has been widely used. There was 

 reason, therefore, to question that the recommended 

 1% was the optimum C0 2 level for macrophytes under the 

 culture conditions employed. In experiments which will 

 not be reported in detail, C0 2 concentrations less than 

 0.4% resulted in a reduced rate of Elodea growth. The 

 rate of growth was, however, not increased by raising the 

 CO2 concentration above 0.4%. The maximum concentration 

 tested was 2.0% which was not inhibitory to the Elodea. 



DISCUSSION 



The nutrient medium for macrophytes developed in this 

 study was demonstrated to produce excellent growth of 

 several species. It is anticipated the medium will be 

 equally suitable for other macrophytes. This optimism 

 is based on general experience with plant culture media. 

 Once the general features of a nutrient medium are established, 

 it usually is satisfactory for many species. Species with- 

 in a major taxonomic group are not sensitive to minor 

 variations in nutrient solution composition. 



Establishing techniques and conditions necessary for 

 laboratory culture of macrophytes should stimulate 

 basic studies on the neglected area of the nutrition 

 and physiology of these organisms. This background 

 information is critical for understanding the behaviour, 

 distribution, and ecology of the macrophytes. Laboratory 

 studies can be particularly useful in providing the basic 

 data on macrophyte nutritional requirements needed in 

 developing measures to control nuisance growths of these 

 organisms . 



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