SOME FACTORS INFLUENCING THE UTILIZATION OF INORGANIC NITROGEN BY THE ROOT ROT FUNGUS

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Abstract
The growth and development of the fungal mats of Phymatotrichum omnivorum in synthetic nutrient media containing different forms of inorganic N were studied. The dry wts. of the fungal mats were used as a measure of the adaptability of the various nutrient solns. to the utilization of the different forms of N. The progressive increase in acidity when ammonium salts are employed prevents the proper evaluation of the nutritive value of this form of N. The decrease in acidity accompanying nitrate absorption favors the development of this rather acidophobic organism. The addition of an excess of the carbonates of Na, Mg, or Ca retards the development of critical acidity when N is supplied by ammonium salts and shows that this form of N is of equal nutritive value to that of nitrates. Tests revealed the ability of the organism to use nitrite N. Ammonium utilization was found to be favored by an increase in phosphates, especially if there was an accompanying increase in Mg. In a like manner an increase in both Ca and sulfate increases growth with this form of N. An excess of both Mg and sulfates retards or suppresses growth. The balance between K and Mg was found to be critical in the utilization of nitrate N.