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Variations in the amino acid composition of xylem sap of Betula pendula Roth. trees due to remobilization of stored N in the spring
Author(s) -
Millard P.,
Wendler R.,
Hepburn A.,
Smith A.
Publication year - 1998
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.1998.00313.x
Subject(s) - xylem , betula pendula , annual growth cycle of grapevines , botany , growing season , biology , chemistry , horticulture , shoot
Seasonal patterns of N translocation in the xylem sap of Betula pendula were studied, to determine whether specific amino acids were recovered in spring as a consequence of N remobilization. Seedlings were grown in sand culture and provided with 15 NH 4 15 NO 3 (at 2·2 atom percent excess) for one growing season. The following winter dormant trees were transplanted into fresh sand and given N at natural abundance thereafter. Destructive harvests were taken during bud burst and leaf growth to determine the pattern of 15 N remobilization and N uptake, along with isolation of xylem sap for analysis of their amino acid profiles and 15 N enrichment by GC‐MS. 15 N remobilization occurred immediately following bud burst, while N derived from root uptake did not appear in the leaves until 12 d after bud burst. During N remobilization there was a 10‐fold increase in the concentration of N in the xylem sap, due predominantly to increases in citrulline and glutamine. The 15 N enrichment of these two amino acids demonstrated the increase in their concentration in the xylem sap following bud burst was due to N remobilization. These results are discussed in relation to measuring N remobilization and storage capacity of trees in the field.