The relationship between N/S ratios and ATP sulfurylase activity indicates that S content does not control enzyme activity once adequate sulfur is present. N metabolism may be the limiting factor. This is consistent with the known lack of response to sulfur fertilization once adequate levels have been attained. A survey of ATP sulfurylase activity in six commercial varieties and 20 soybean [ Glycine max (L.) Merrill] lines indicated wide differences in activity. The activity is likely under genetic control. ATP sulfurylase activity did not correlate with seed protein content or with methionine content of the seed protein.
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Adams et al. (1970) studied this question.