EFFECTS OF MYCORRHIZAL COLONIZATION BY PAXILLUS-INVOLUTUS ON UPTAKE OF CA AND P BY PICEA-ABIES AND BETULA-PENDULA GROWN IN UNLIMED AND LIMED PEAT

Uptake of P(P-32) and Ca(Ca-45) by seedlings of Picea abies (L.) Karst and Betula pendula Roth, non-mycorrhizal or mycorrhizal with Paxillus involutus (Batsch: Fr) Fr. was studied. Seedlings were grown in uname nded peat (pH 4.0) or in peat limed (CaO) to pH 5.1 or 6.1. A double-l abelled (P-32 and Ca-45) complete nutrient solution was added to the p eat 7 wk after planting. An 8 d period was allowed for uptake of the i sotopes before the seedlings were harvested. Mycorrhizal colonization clearly increased the uptake of P(P-32) in the unlimed substrate and i n the substrate limed to a pH of 5.1. At the highest lime rate, the up take of P(P-32) was greatly reduced in both mycorrhizal and non-mycorr hizal seedlings. The difference in P uptake between mycorrhizal and no n-mycorrhizal seedlings was small at this lime rate. The mycorrhizal c olonization of the roots was not affected by liming. However, it is po ssible that the mycelial growth into the substrate was inhibited. The reduction in uptake could thus be an effect of a lower availability of P in combination with a decreased fungal uptake surface at the highes t lime rate. The mycorrhizal effect on uptake of Ca was much smaller t han its effect on uptake of P. Mycorrhizal colonization increased the Ca(Ca-45) uptake in the unlimed treatment, where the Ca content in the substrate was very small. In the limed substrates the uptake of Ca wa s as high or higher in the non-mycorrhizal than in the mycorrhizal see dlings.