A study of ageing of spruce [Picea sitchensis (Bong.) Carr.] ectomycorrhizas. II. Carbohydrate allocation in ageing Picea sitchensis/Tylospora fibrillosa (Burt.) Donk ectomycorrhizas.

Translocation of C-labelled photosynthate was studied in seedlings of Picea sitchensis (Bong.) Carr. ectomycorrhizal with Tylospora fibrillosa (Burt.) Donk grown in Perspex observation chambers. Although translocation to young and older mycorrhizas was observed, accumulation of current C-labelled photosynthate was reduced in older compared with young mycorrhizas in the same root system. Non-structural carbohydrate components of P. sitchensis/T. fibrillosa and undefined beech ectomycorrhizas collected from the field were quantified by gas-liquid chromatography. Relative differences in accumulated carbohydrates were identified between P. sitchensis/T. fibrillosa and beech mycorrhizas. Levels of total soluble and insoluble carbohydrate were lower in older compared with young P. sitchensis/T. fibrillosa mycorrhizas. The soluble sugars arabitol, glucose and mannitol were detected in significantly lower quantities in older mycorrhizas whilst fructose and trehalose content was similar to that of young mycorrhizas. These results are discussed in relation to the physiology of the ageing mycorrhiza.