Editorial

This special issue celebrates the completion of the poplar genome sequencing project. We expect that the availability of the full genomic information for poplar will have the same impetus on all areas of tree research as the publication of the Arabidopsis genome is currently having on all fundamental aspects of plant biology.

Why do we expect that the poplar genome sequence will trigger significant scientific progress, beyond what can expected from Arabidopsis research? In this context, it is worthwhile to mention that trees are not just “bigger” than Arabidopsis plants. An important difference is the long life cycle of trees, which may take decades or even centuries from germination, seedling establishment, juvenility, maturity, senescence and finally death. To survive these long periods of time, trees have evolved a number of special adaptations with respect to structural support, nutrition, and stress resistance, which are absent or only partially present in annual herbs.

Temperate trees cycle seasonally through phases of active growth and dormancy. The tightly regulated activity of the secondary cambium results in the development of the trunk, typical of trees. Furthermore, storage and reallocation of nutrients in autumn and remobilization in spring are of particular importance for the annual leaf flush and wood development. Trees can colonize nutrient-poor habitats, as found in many forest ecosystems, because of their symbiotic association with mycorrhizal fungi. Trees are tolerant of extended or annually recurring stresses, such as drought, heat, frost, or unfavorable soil conditions, and display special adaptive mechanisms, such as seasonal changes in stress tolerance or increases in regenerative power under stress. The genus Populus is extremely flexible in this respect because it contains a wide variety of species with different degrees of stress tolerance and varying growth characteristics.

Unlike Arabidopsis, trees also have important economic applications. In many countries, large reforestation projects have been initiated with the aim of rapid wood production for industrial purposes, such as pulp and paper production, or to provide renewable energy. Trees are also utilized for environmental protection, e.g., to prevent soil erosion, landslides, avalanches or to achieve phytoremediation of contaminated soils.

These examples show that tree growth, development, and performance are of broad interest from both the ecological and the economic points of view. Research into questions of tree nutrition, wood formation, and stress resistance will be stimulated and facilitated by the genomic information that has become available from the poplar genome sequencing project. The PRG (Poplar Research Group, Germany), kindly supported by the German Science Foundation (DFG), will take advantage of this important development.

Renowned scientists from all over the world have contributed to this special issue that covers many aspects of poplar phenology, physiology, and molecular biology. In addition, papers addressing new methodological approaches to investigate tree-specific questions have been included. We hope that the readers of PLANT BIOLOGY will enjoy this selection of papers on recent developments in poplar biology.

Andrea Polle, Universität Göttingen

Heinz Rennenberg, Universität Freiburg