Use of labeled nitrogen to monitor transition in nitrogen dependence from storage to current-year uptake in mature walnut trees
✍ Scribed by X. Deng; S. A. Weinbaum; T. M. DeJong
- Publisher
- Springer-Verlag
- Year
- 1989
- Tongue
- English
- Weight
- 516 KB
- Volume
- 3
- Category
- Article
- ISSN
- 0931-1890
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✦ Synopsis
Nitrogen (N) derived from both the soil during current-year uptake, and the withintree pool of storage N was distinguished in two groups of "Serr" walnut trees using labeled fertilizer (tSN-depleted ammonium sulfate) applied in different years. Mass spectrometric analysis of N in xylem sap collected periodically in spring allowed quantification of the relative contributions of N from storage and current season uptake and the transition in N usage from previously assimilated (storage) N to the onset of current season uptake of soil N. N derived from storage accounted for > 50% of the xylem sap N during the staminate and pistillate bloom periods and throughout the period of spur leaf expansion.