| Abstract | Soybean (Glycine max L. cv. Mandarin) and wheat (Triticum monococcum L.) cells were grown in media with NO₃⁻ plus NH₄⁺(B₅) and NO₃⁻ without NH₄⁺ (B₅-NH₄) as nitrogen sources. Changes in pH, [NO₃⁻] and [NH₄⁺] in media, and dry weight, protein content, nitrate reductase (NR) and glutamate dehydrogenase (GDH) in the cells were followed for about 170 h. With both NH₄⁺ and NO₃⁻ in the medium, NH₄⁺ was utilized very quickly. Soybean cells grew poorly in the absence of NH₄⁺ while wheat cells grew equally well on media with or without NH₄⁺. When soybean cells were grown in medium with NO₃⁻ plus NH₄⁺, dry weight and NR activity remained relatively low for several hours after which both increased rapidly. This coincided with the time NH₄⁺ was depleted from the medium. In the absence of NH₄⁺, soybean cell growth and NR activity remained low. NR activity in wheat cells, and GDH activity in soybean and wheat cells, did not vary significantly in the presence or absence of NH₄⁺. |
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