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Keywords:

  • buckling safety factor;
  • lignin;
  • stem form;
  • tension wood;
  • transgenic poplar;
  • wood stiffness;
  • wood strength

Summary

  • Reduced lignin content in perennial crops has been sought as a means to improve biomass processability for paper and biofuels production, but it is unclear how this could affect wood properties and tree form.
  • Here, we studied a nontransgenic control and 14 transgenic events containing an antisense 4-coumarate:coenzyme A ligase (4CL) to discern the consequences of lignin reduction in poplar (Populus sp.). During the second year of growth, trees were grown either free-standing in a field trial or affixed to stakes in a glasshouse.
  • Reductions in lignin of up to 40% gave comparable losses in wood strength and stiffness. This occurred despite the fact that low-lignin trees had a similar wood density and up to three-fold more tension wood. In free-standing and staked trees, the control line had twice the height for a given diameter as did low-lignin trees. Staked trees had twice the height for a given diameter as free-standing trees in the field, but did not differ in wood stiffness.
  • Variation in tree morphogenesis appears to be governed by lignin × environment interactions mediated by stresses exerted on developing cells. Therefore our results underline the importance of field studies for assessing the performance of transgenic trees with modified wood properties.