The Assimilate Partitioning Importance for Heartwood Extractives Formation in Robinia Pseudoacacia l. of Different Ages

Importância da Distribuição de Assimilados para a Formação dos Extrativos do Cerne em Robinia Pseudoacacia L. de Diferentes Idades

ABSTRACT

This study aimed to investigate the influence of tree age on the assimilates partitioning and its significance for the formation of heartwood extractives in Robinia pseudoacacia L. (black locust). Assimilate translocation in 6- and 15-year-old plants was measured in May and August 2006 using the ¹⁴CO₂ feeding method. The heartwood extractives content in the sapwood-heartwood transition zone and in individual tree rings of the pure heartwood were analysed by HPLC-chromatography. All plants, buds and young leaves showed the strongest 14C specific activity compared to other plant parts in May and August(¹⁴C specific activity in buds/leaves of 6-years old plants: 35.2-37.0%, 15-years old plants: 31.4-32.2%). However, in plants labelled in August 2006 at the sapwood-heartwood transition zone also showed a strong assimilates sink, while only small amounts of assimilates were translocated to the sapwood-heartwood transition zone in the plants labelled in May 2006. The amount of assimilates transported to the sapwood-heartwood transition zone was significantly higher in the 15-year-old plants compared to the 6-year-old plants. This was monitored by a higher content of extractives in the heartwood formed by the older plants compared to heartwood formed by the younger plants. The results indicate that uneven assimilate partitioning in younger and older black locust plants affects the heartwood extractives formation, which might lead to a lower natural durability of the heartwood formed by younger trees compared to heartwood formed by older trees.

Keywords:
juvenile wood; mature wood; heartwood durability; assimilate labelling