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  • Author or Editor: Robert A. Pierpont x
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Seedlings of tomato (Lycopersicon esculentum Mill.) (15 to 22 days old) exposed to unbuffered solutions containing N solely in the NH4 form showed poorly developed, thickened, less branched, discolored root systems, marginal necrosis of some leaves, wilting, particularly dark green foliage, and restricted growth. Calcium carbonate at 0.5 g/liter alleviated NH4 toxicity and restricted the accumulation of free NH4 in roots, bleeding sap, and shoots even though NH4 uptake rates were accelerated by CaCO3. Thus, the beneficial effect was related to enhanced NH4 assimilation. Roots contained an active NADH-specific L-glutamate dehydrogenase, but in vitro activity was correlated with internal NH4 content and, therefore, did not reflect actual NH4 assimilation rates during experimental periods.

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