© 2004 Heron Publishing—Victoria, Canada
Boron retranslocation in Scots pine and Norway spruce
Tarja Lehto (1, 2), Anu Lavola (1, 3), Riitta Julkunen-Tiitto (3) and Pedro J. Aphalo (1, 4)
1. University of Joensuu, Faculty of Forestry, P.O. Box 111, 80101 Joensuu, Finland / 2. Corresponding author (tarja.lehto@joensuu.fi) / 3. University of Joensuu, Department of Biology, P.O. Box 111, 80101 Joensuu, Finland / 4. University of Jyväskylä, Department of Biological and Environmental Science, P.O. Box 35, 40351 Jyväskylä, Finland / Received December 5, 2003; accepted January 26, 2004; published online July 1, 2004
Summary
We previously traced 10B-enriched boric acid from shoots to roots to demonstrate the translocation of boron (B) in Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings. To gain a more detailed understanding of B translocation, we sought: (1) to demonstrate B retranslocation
directly, by showing that foliar-applied 10B is located in the new growth after dormancy; and (2) to assess whether shoot-applied B affects growth in the long term.
We applied 10B-enriched boric acid to needles of Scots pine and Norway spruce seedlings. After a dormancy period and 9 weeks of growth,
small but significant increases in the 10B isotope were found in the new stem and needles of both species. In Scots pine, the total B concentration of the new stem
was also increased. Both species contained polyols, particularly pinitol and inositol. Boron–polyol complexes may provide
a mechanism for mobilizing B in these species.
To determine the long-term effects of applied B, seedlings were grown for two growing seasons after the application of 10B to shoots. In Norway spruce, the proportion of 10B in the root systems and current needles of the harvest year was slightly higher than in the controls, and in Scots pine
root systems, marginally so. The B treatment had no effect on growth of Norway spruce seedlings. In Scots pine seedlings,
the B treatment caused a 33% increase in total dry mass and significantly increased the number of side branches.
Keywords:
mineral nutrients, Picea abies, Pinus sylvestris, stable isotopes.
