Effect of nitrogen nutrition on amino acid composition of xylem sap and stem wood in Alnus glutinosa

Abstract

Citrulline was the major amino acid in root pressure sap, stem sap and stem wood from Alnus glutinosa L. Gaertn. plants relying on fixed nitrogen or, partly or wholly, on mineral nitrogen for growth. Glutamine increased in prominence in plants assimilating mineral nitrogen but asparagine remained a relatively insignificant component. Differences in the relative amounts of the free amino compounds of stem sap from nitrogen‐fixing and mineral nitrogen‐fed plants were usually small compared to differences between plants fed different sources of mineral nitrogen. In contrast, relatively high values for the ratios of citrulline/total free amino nitrogen compounds and particularly of citrulline/amides in root pressure sap distinguished nitrogen‐fixing plants from those receiving mineral nitrogen. Although the amino acid ratios of stem wood extracts showed closer similarity to those for root pressure sap than stem sap, the seasonal accumulation of citrulline, possibly as a storage amino acid, in stem wood from field‐grown plants negated the possibility of utilising stem wood analyses as an indicator of the form of nitrogen assimilation. Comparative data on the levels of citrulline or other free amino acids in Alnus glutinosa are unlikely to be useful as an index of nitrogen fixation, under most experimental conditions.

Primary metabolism in N2-fixing Alnus incana?Frankia symbiotic root nodules studied with 15N and 31P nuclear magnetic resonance spectroscopy

“…Cit is not specific for N 2 -fixing plants but among actinorhizal plants, i.e. plants having a root nodule symbiosis with Frankia, it can in the genera Alnus and Casuarina be the most abundant amino acid in the xylem sap and/or root nodules (Miettinen and Virtanen 1952;Wheeler and Bond 1970;Schubert et al 1981;Hafeez et al 1984;Tonin et al 1990; Sellstedt and Atkins 1991;Baker et al 1997;Lundquist et al 2003).…”

Spatial and temporal variations in phloem sap composition of plantation-grown Eucalyptus globulus

“…For other tree genera, a number of authors have commented similarly on the utility of xylem sap analysis for diagnostic purposes, especially in studies of soil nutrient availability and tree nutrient status and growth potential (e.g. see Berger et al 1994;Dambrine et al 1995;Kazda and Weilgony 1988;Stark et al 1984Stark et al , 1989Tonin et al 1990;Walsh et al 1984). Nevertheless, analyses of xylem sap alone are likely to constitute poor indicators of nutritional condition because of complications arising from (a) transient and long-term storage of xylemdelivered nutrients in mature parts of shoots and roots (e.g.…”

Citric acid in tomato plant roots and its effect on cadmium uptake and distribution

“…Plant roots are generally considered to be involved in processes of synthesis, uptake and release of organic acids (Collins and Reilly, 1968;Tonin et al, 1990).…”