Eight enzymes concerned with carbohydrate metabolism, extracted and partially purified from mycorrhizal roots of beech, were studied to determine the possible role of a number of sugar alcohols (polyols) as effectors for the carbohydrate metabolism of the roots.

Various patterns of inhibition of these enzymes by different polyols were found. Mannitol and threitol were the most effective of the polyols studied in terms of the number of enzymes affected and the apparent inhibition constants for the affected reactions. None produced an activation of the enzyme reactions.

The possible significance of these enzyme inhibitions as indicating ways in which the presence of the sheath of fungal mycelium may alter the utilization of carbohydrate in the tree and result in translocation to the symbiotic fungus, and the relation of these findings to the known characteristics of mycorrhizas are discussed.