Sutinen, S. and Saarsalmi, A. 2008. Needle Structure in Relation to Boron Fertilization in Picea abies (L.) Karst. Stands Suffering from Growth Disturbance.   Baltic Forestry 14 (2): 98-102

Bushy growth, a typical symptom of boron (B) deficiency, has caused enormous economical losses in Norway spruce (Picea abies (L.) Karst.) stands in extensive areas in eastern central Finland, and thus has created a need to determine ways of protecting forest health and productivity. To find out if microscopy could have potential for a diagnostic tool of B deficiency before visible damage, B concentrations, number of sclerenchyma cells earlier connected to B availability, and the area of central cylinder earlier connected to water availability, were studied in the current needles from about 30-year-old mature healthy (H) and damaged (D) spruce trees in autumn of B fertilization and two years later in eastern central Finland. The treatments, given on 15-17 May 2000, were:no fertilization (0), B supply (B; 2.0 kg B ha¨¹ as borax), B+P supply (B+P; 2.0 kg B ha¨¹ and 40 kg P ha¨¹ as superphosphate) and N supply (N; 200 kg N ha¨¹ as urea). The needle B concentrations significantly increased in the trees given B, and were higher in the needles from healthy (H) trees compared to those from damaged (D ) trees. This difference reduced by the third autumn indicating recovery of the roots of the trees, which showed recovery of shoots in earlier study. The area of the central cylinder reflected water availability during needle development. The number of sclerenchyma cells was low in needles from 0 (no fertilization) and N trees and increased in trees fertilized by B and B+P. Low number of sclerenchyma cells has potential for diagnose the B deficiency, but more background knowledge about the effects of other stress factors is still needed.

Key words: boron deficiency, bushy growth, light microscopy, needle, Norway spruce