Abstract
Summary: The effects of ammonium chloride, potassium nitrate and potassium chloride on the rate of 14CO2 incorporation into beech mycorrhizas were compared. It was confirmed that the rate of incorporation of 14CO2 was increased by ammonia and that glutamine became heavily labelled in its presence. No such effect was evident in the case of nitrate. Both potassium chloride and potassium nitrate stimulated 14CO2 incorporation as compared with samples kept in water but the extra radioactivity was found primarily in malate. This is the result to be expected if potassium is absorbed more readily than the associated anion. It is concluded that nitrate is not readily utilized by excised beech mycorrhizas. The primary destination of absorbed ammonia appears to be the fungal sheath.