Effects of boron nutrition, temperature, and moisture on growth traits of white and Norway spruce seedlings

Abstract

This study investigated the effects of foliar boron concentrations on growth characteristics of white spruce (Picea glauca (Moench) Voss) and Norway spruce (Picea abies (L.) Karst.), emphasizing interactions with temperature, moisture, and potential carry-over effects across growing seasons. Controlled growth chamber and greenhouse experiments assessed seedling growth, including preformed-shoot characteristics, and reflush responses. Low boron did not consistently induce deficiency symptoms in white spruce, whereas moisture stress strongly influenced seedling growth and exerted legacy effects in the following season. Under high boron, morphological growth traits (root dry weight and root collar diameter) were affected only when foliar concentration exceeded 825 ppm, while needle discoloration and terminal bud anomalies occurred at levels below 100 ppm. Norway spruce exhibited greater sensitivity than white spruce, with toxicity observed at foliar concentrations below currently accepted thresholds. Overall, the findings underscore species-specific boron responses and the need to refine nursery nutrient and water management practices.