Annals of Botany 39: 347-361, 1975
© 1975 Annals of Botany Company
RESEARCH-ARTICLE |
The Utilization of P—N Compounds by Plants II. The Role of Extracellular Root Phosphatases
Department of Plant Sciences, University of Leeds Leeds
1 Present address: Department of Biological Sciences, University of Natal, Durban, 4001, South Africa.
Received: 20 May 1974
Barley plants were grown on culture solutions containing sodium phosphodiamidate as the sole source of both phosphorus and nitrogen. The compound hydrolysed more rapidly in solutions on which plants were growing than in a similar solution without plants, supporting the hypothesis of a root-mediated hydrolysis. Histochemical tests provided corroborative evidence for root-mediated hydrolysis of phosphodiamidate and indicated that some of this hydrolytic activity was probably associated with the cell wall. Purified root cell wall preparations catalysed the hydrolysis of phosphodiamidate, the activity being firmly bound to the cell wall. Some evidence was obtained to show that this activity was enzymic in nature, rather than a general surface catalysis. Competitive inhibition by ß-glycerophosphate suggested that the hydrolysis of the phosphodiamidate was brought about by a non-specific phosphatase, rather than a phosphoamidase as such. The activity was shown to be constitutive. It was concluded that the main mechanism by which plants utilize phosphodiamidate as a nutrient source involves hydrolysis of the compound at the root surface, probably by a constitutive, non-specific phosphatase, and subsequent uptake of the phosphate and ammonia produced by hydrolysis.