Does water-stress lead to formation of traumatic tissue and tracheid collapse in poorly lignified Pinus radiata?

Copper deficiency and stem deformation have been linked to poor lignification in Pinus radiata and in non-woody species. Tracheid collapse in zones of poorly lignified woody tissue from deformed Pinus radiata has also been reported. This paper reports an experiment to investigate whether tracheid collapse in poorly lignified wood from Cu-deficient plants can be caused by water-stress.

Seedlings from two families of P. radiata were grown in a peat/sand mix and subjected to stages of water-stress after symptoms of stem and branch deformation had become apparent. The final stage of water-stress was sufficient to kill the seedlings.

Woody tissue was poorly lignified, and seedlings had very low concentrations of copper in foliage (1.1 μg g⁻¹). However, collapsed tracheids were not evident in poorly lignified wood after water-stress had been applied. The results indicated that previously reported tracheid collapse in deformed and poorly lignified stems of P. radiata was not caused by water-stress.

There were significant differences in stem deformation between the two seedling families.