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Effect of artificial defoliation on biomass allocation in ectomycorrhizal Pinus sylvestris seedlings

Markkola, A.M.
Canadian journal of forest research = 1996 v.26 no.5 pp. 899-904
Pinus sylvestris, seedlings, defoliation, shoots, roots, conifer needles, seedling growth, ectomycorrhizae, biomass production
Ectomycorrhizal seedlings of Scots pine (Pinus sylvestris L.) were subjected to repeated artificial defoliation (0, 25, 50, and 75%) to demonstrate the effect of a reduced amount of photosynthates on the allocation of biomass between the tree and its fungal symbionts. Defoliation reduced shoot biomass in the seedlings significantly, and belowground parts adjusted to the same growth level. Biomass parameters of seedlings that had undergone the mildest defoliation treatment did not differ significantly from control seedlings, while the two most intensive treatments reduced growth and biomass of seedlings in a similar way. Defoliation did not reduce mycorrhizal colonization or fungal biomass calculated per unit weight of fine roots. Actual needle biomass in seedlings correlated positively with stem biomass, total root biomass, fungal biomass both in roots and in soil, and the number of mycorrhizal root tips per seedling. Root/shoot ratio and total allocation pattern were relatively constant.