Soluble carbohydrates, radial growth and vigour of fertilized Norway spruce after inoculation with blue-stain fungus, Ceratocystis polonica

Abstract.

The aim of this study was to determine whether fertilization and the consequent increase in growth reduce the allocation of soluble carbohydrates in response to an induced wound. Norway spruce trees fertilized with N, P or NPK were artificially infected with Ceratocystis polonica, a blue-stain fungus associated with the spruce bark beetle Ips typographus. N and NPK fertilization treatments increased radial growth of the stem and the vigour indices. The concentration of total soluble carbohydrates in the outer border of the lesion was significantly decreased in P-fertilized trees compared to corresponding unfertilized trees. However, changes in the soluble carbohydrate concentration caused by fungal inoculation were more pronounced than changes caused by fertilization. The main soluble carbohydrate was sucrose, and after fungal inoculation its concentration decreased considerably near the site of inoculation. Thus, near the site of fungal inoculation the concentration of total soluble carbohydrates also decreased significantly compared to corresponding values in unwounded phloem. Despite the fact that in all fertilized trees the radial growth of the stem increased, the only indication that enhanced growth might reduce the level of resistance was the modest positive correlation between lesion length and radial growth of the stem.