Effect of applied nutrients and endomycorrhizas on Metrosideros umbellata and Leptospermum scoparium

Abstract

Leptospermum scoparium ceased growth and Metrosideros umbellata grew only slowly in Te Anau soil (3 μg half hour Olsen extractable P) unless infected by vesicular-arbuscular mycorrhizas or given additional phosphorus. Mycorrhizas stimulated P uptake but did not always supply the host's full P requirements.

High shoot P concentrations efTccted by applying P reduced mycorrhizal infection. In L. scoparium shoot P rose to a toxic level but the fungus was not eliminated.

The application of nutrients other than P stimulated growth of mycorrhizal plants, generally lowered the concentration of P in the shoots, and clfected an increase in infection levels. Because of the presence of residual infections, it was concluded that infection level is only an indication of a host's mycotrophic status when it is known the endophyte is benefitting growth.