CALCIUM 



311 



(155). The valence states of molybdenum which function in electron 

 transport are the +5 and the +6 (171). 



Molybdenum must, however, have other functions, inasmuch as a 

 molybdenum deficiency can be demonstrated in media not containing 

 nitrate (152, 168, 170). 



10. CALCIUM 



The effect of calcium on the growth of fungi has only recently been 

 recognized, although the first report of such an effect was in 1922 (258). 

 Species in 19 genera, including representatives of all the major groups 

 of fungi and of the genus Streptomyces, have been found to respond to 

 added calcium by an increase in dry weight (62, 63, 73, 99, 113a, 117, 

 128, 166, 175, 178, 198, 239, 246, 253). Reported optima range from 

 0.5 to 20 ppm. Some fungi, it should be noted, cannot be shown to 

 require calcium (198, 239). Figure 3 illustrates the response to cal- 

 cium. 



Strontium partially replaces calcium for Allomyces arbuscula (99) 

 and several other fungi (117, 198, 239). Strontium is firmly bound by 

 mycelium of Rhizopus sp. (116). 



One may still ask, however, whether the so-called calcium require- 



7 9 



Time, days 



Figure 3. The growth of Coprinus ephemeras at different levels of calcium 

 (milligrams per liter). Redrawn from Fries (63), by permission of the Svensk 

 Botanish T.idskrift. 



