Nitrogen-containing Compounds in the Shoot System of Pisum arvense L.

Abstract

A pulse-labelling technique is described for applying specific radio substrates to detached shoots via the transpiration stream. Unlabelled bleeding sap is used as a carrier for the substrates and as a chaser during a further period of assimilation. The substrates studied are 14C-U-aspartic acid, 14C-U-asparagine, 14C-U-gluta-mic acid, 14C-U-glutamine, 14C-homoserine, 14C-2-glycine, and metabolically labelled samples of bleeding sap. All substrates contribute carbon to chloroform-soluble and water-soluble substances, and to the protein and other insoluble constituents of the shoot. Each substrate makes a characteristic contribution of carbon to the soluble reserves and protein of the shoot. Members of the aspartate and glutamate families of amino-acids dominate among the products labelled during assimilation of the five radiosubstrates which are regular constituents of the sap. Results are contrasted with feeding 14C-2-glycine, an amino-acid normally absent from the bleeding sap.