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

Oliver Dünisch,João Vicente De Figueiredo Latorraca

doi:10.1590/2179-8087.083514

Oliver Dünisch, João Vicente De Figueiredo Latorraca

Open Access

https://doi.org/10.1590/2179-8087.083514

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Abstract

ABSTRACTThis 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.

Highlights

During the last years, the demand for highly durable timber strongly increased
Similar results are reported for Robinia pseudoacacia L., one of the most promising species for the production of highly durable heartwood in North America and in Europe (Stringer & Olson, 1987; Adamopoulus et al, 2005)
The analyses of heartwood extractives in individual tree rings from the cambium to the pith showed that heartwood formation starts in the third growth increment and is completed after 2 to 3 years as a maximum

Summary

Introduction

The demand for highly durable timber strongly increased. Tree species, which produce timber of a high natural durability have been heavily exploited in natural forests, leading to low remaining stocks of old-grown trees. Reports from practice indicated a decrease of natural durability of the heartwood of timber from some species, which are considered to produce the best quality of timber for outdoor constructions. There is a high number of further high quality timber species without significant differences in the natural durability of the heartwood formed during the juvenile phase of growth and the adult phase of growth (Zobel & Sprague, 1998)

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