Tomato ( Lycopersicon esculentum Mill. cv. Heinz 1350) plants grown in soil with N supplied from (NH 4 ) 2 SO 4 solutions showed a morphological disorder characterized by leaf epinasty. The development of this disorder was accompanied by an increase in the rate of ethylene evolution from whole plants. Ethylene evolution from plants supplied with 0.04 m NH 4 -N increased to a peak of 112 nl·g −1 ·hr −1 at ≈2 weeks following the start of fertilization compared to 11 nl·g −1 ·hr −1 from plants supplied with 0.04 m NO 3 -N. Fertilization with KC1 in molar equivalency to the supply of NH 4 -N prevented epinasty and the burst in ethylene evolution. Ethylene evolution from plants of the yellow-green -5 and neglecta -1 mutants did not increase in response to NH 4 -N fertilization. Potassium concentrations in shoots of ‘Heinz 1350% yellow-green - 5, and neglecta -1 were 2.10, 2.53, and 3.22% (dry weight), respectively, if plants were supplied with NH 4 -N and no additional K, suggesting that tolerance to NH 4 toxicity may be explained in part by differences in K accumulation.
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Corey et al. (1987) studied this question.