A HISTOCHEMICAL STUDY OF POLYSACCHARIDE DISTRIBUTION IN EUCALYPT MYCORRHIZAS

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Abstract
SUMMARY: This paper describes a histochemical study of the distribution of polysaccharides in un‐infected and mycorrhizal Eucalyptus fastigata roots. The most striking influence of mycorrhizal infection is the suppression of starch accumulation in the root cap cells and meristematic region of the root. In addition, there is a very substantial reduction in the amount of acidic polysaccharide (root cap slime) accumulated around the outer root cap cells in mycorrhizal roots, compared with uninfected roots. These observations generally hold for roots collected from a wide variety of conditions and at different times of the year. The reduction in amounts of these two important polysaccharides is presumed to result from lack of availability of precursors for polysaccharide synthesis, due to diversion of carbohydrate into the fungus partner. The histochemical observations in E. fastigata mycorrhizas are thus in accord with experimental data from other mycorrhizas which indicate transfer of large quantities of carbohydrate from root to fungus, and suggest that carbohydrate transfer is likely also to occur in mycorrhizas of E. fastigata.