M. Mottonen et al., Growth dynamics and mycorrhizas of Norway spruce (Picea abies) seedlings in relation to boron supply, TREES, 15(6), 2001, pp. 319-326
The effects of three boron levels on the growth dynamics and ectomycorrhiza
s of seedlings of Norway spruce [Picea abies (L.) Karst.] were studied in a
growth room experiment. The seedlings were grown in forest humus mixed wit
h quartz sand for 16 weeks. The B treatment was applied in the nutrient sol
ution. Stem height, dry weight, number of root tips, mycorrhizas as well as
B and N concentrations in the seedlings were monitored in sequential harve
sts. By the last harvest, in week 16, needle B concentrations were 6.6 mg k
g(-1) at the lowest B level and 17.5 mg kg(-1) and 26.5 mg kg(-1) at the tw
o higher levels. Boron slightly increased the stem hei-ht and the total dry
weight, but did not affect N content of the seedlings. Low internal B redu
ced the number of root tips and mycorrhizas as well as mycorrhizal percenta
ge and root dry weight, which indicates the importance of B for root growth
in Norway spruce seedlings. The seedlings crown with adequate internal B h
ad more root tips than those receiving the two lower B treatments as early
as week 9, when needle B concentrations at the lowest B supply were 16.0-17
.3 mg kg(-1), which has previously been considered a sufficient B level. Th
erefore, the critical needle B concentrations should perhaps be re-examined
.