Interaction of cyanide with nitrogen metabolism in wheat ( Triticum aestivum)

The uptake and assimilation cyanide has been implicated in plant nitrogen metabolism. The overarching objective of this research was to determine the contribution of cyanide to nitrogen metabolism in wheat (Triticum aestivum). More specifically, this research sought to determine if cyanide was preferentially assimilated over ammonium and to determine the response of the beta-cyanoalanine metabolic pathway to environmentally relevant concentrations of cyanide. A labeling experiment was conducted, employing reciprocal treatments with KC15N or 15NH 4Cl, to determine the interaction of ammonium and cyanide with regard to N uptake in wheat seedlings. Ammonium did not seem to interact with cyanide uptake with only one exception; plants not receiving ammonium appeared accumulate higher quantities of cyanogenic nitrogen at the root level. Cyanide did not appear to alter ammonium uptake. However, ammoniacal nitrogen was clearly preferred over cyanogenic nitrogen. Tissues of seedlings treated with 15NH were twice as abundant in 15N than tissues of seedlings treated with KC15N.; The primary enzyme of the beta-cyanoalanine pathway, beta-cyanoalanine synthase (CAS; EC 4.4.1.9), did not appear to respond to low-level cyanide treatment after 24 h of exposure. A constitutive role for CAS in cyanogenic nitrogen uptake and assimilation is suggested.