ABSTRACT
This optimal utilisation of the available nitrogen stock in soil by ectomycorrhizal plants has a fundamental ecological significance in the overall nitrogen cycle of forest populations (Alexander, 1983; Read, 1991). It is important to note that most, if not the total nitrogen flux transiting from the soil to the root, must cross the barrier constituted by the fungal ectomycorrhizal mantle before reaching the root cortex. Understanding the processes of absorption and assimilation of nitrogen in trees necessarily requires characterisation of nitrogen metabolism in the associated fungi. This role of the fungal partner is all the more pronounced in root systems of trees, the major site of nitrogen metabolism (Stewart et ah, 1989).
