EFFECT OF ARTIFICIAL DEFOLIATION ON BIOMASS ALLOCATION IN ECTOMYCORRHIZAL PINUS-SYLVESTRIS SEEDLINGS

Ectomycorrhizal seedlings of Scots pine (Pinus sylvestris L.) were sub jected to repeated artificial defoliation (0, 25, 50, and 75%) to demo nstrate the effect of a reduced amount of photosynthates on the alloca tion 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 seedli ngs that had undergone the mildest defoliation treatment did not diffe r significantly from control seedlings, while the two most intensive t reatments reduced growth and biomass of seedlings in a similar way. De foliation did not reduce mycorrhizal colonization or fungal biomass ca lculated per unit weight of fine roots. Actual needle biomass in seedl ings correlated positively with stem biomass, total root biomass, fung al biomass both in roots and in soil, and the number of mycorrhizal ro ot tips per seedling. Root/shoot ratio and total allocation pattern we re relatively constant.