INFLUENCE OF ENVIRONMENTAL-FACTORS ON ECTOMYCORRHIZAL INFECTION IN AXENICALLY CULTURED EUCALYPT SEEDLINGS

The paper-sandwich technique for axenic synthesis of ectomycorrhizae w as used to study the effect of various environmental factors on mycorr hizal formation by eucalypt seedlings. This technique involves growing plant roots and fungus separately, then bringing them together in a w ay which immediately initiates infection. Altering either temperature or the carbohydrate status of the fungus markedly affected the proport ion of root apices converted to mycorrhizae. However, altering the lig ht regime or nitrogen and phosphorus availability within wide limits d id not affect the proportion of root apices converted to mycorrhizae. We conclude that infectibility of similar root apices remained constan t throughout these experiments, and that those changes in the environm ent which affected the proportion of roots becoming mycorrhizal were m ediated through effects on the colonisation capacity of the fungal par tner.