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Keywords:

  • 13C;
  • 15N;
  • carbon and nitrogen transport;
  • invertase;
  • jasmonate (JA);
  • polyphenols;
  • Populus;
  • sink strength

Summary

  • Here, we examined the impact of jasmonate (JA) treatment, branching and phloem girdling on 13C and 15N import, invertase activity and polyphenol accumulation in juvenile tissues of unbranched and branched hybrid poplar saplings (Populus nigra × P. deltoides).
  • The import of 13C to juvenile tissues was positively correlated with invertase activity at the treatment site and enhanced by JA. Both invertase activity and 13C import were greater in shorter, younger branches and smaller, younger leaves. By contrast, JA treatments, branching and girdling had little or no impact on 15N import.
  • In poplar saplings with multiple lateral branches, we observed almost no 13C movement from subtending source leaves into lateral branches above them, with or without JA treatment. The presence of potentially competing branches, treated with JA or not, girdled or not, had no impact on carbohydrate (CHO) import or polyphenol accumulation in target branches.
  • We conclude that poplar branches comprise modules that are relatively independent from each other and from the stem below in terms of CHO movement, carbon-based defence production and response to elicitors. By contrast, branches are closely linked modules in terms of nitrogen movement. This should produce trees that are highly heterogeneous in quality for herbivores.