USEFULNESS OF THE PINNULE TECHNIQUE IN MYCORRHIZAL RESEARCH

This chapter is concerned with the determination of pinnule P status as a rapid and precise technique for monitoring the development of symbiotic effectiveness in the vesicular-arbuscular mycorrhizal association. The key criteria to be considered in selecting indicator plants for the pinnule technique are: (1) they must have compound leaves, (2) they must grow reasonably rapidly, (3) they must be moderately to very highly dependent on vesicular-arbuscular mycorrhizal fungi, and (4)they must have pinnules or subleaflets that detach readily from leaflets. Species that are marginally dependent on vesicular-arbuscular mycorrhizal fungi could serve as indicator plants, but the range of soil solution P levels at which they would be useful is limited. Further, the growth conditions are discussed in the chapter. The rule of thumb is that the health of the vesicular-arbuscular mycorrhizal symbiosis is intimately linked to the health of the host plant. Growth conditions must, therefore, be adjusted such that indicator plants will develop and grow normally in the presence of effective vesicular-arbuscular mycorrhizal endophytes. Phosphorus level is particularly critical because appears to be the most important regulator of the symbiosis. © 1992 Academic Press Limited