ABSTRACT
Although it is the common opinion that maintenance and competitiveness of roots are main determinants of plant survival, roots are seldom discussed and considered in studies of plant communities. The role of plant roots in natural environments is complicated by the fact that the great majority of plant species form mycorrhizae. The fine roots that perform most of the uptake activities are symbiotically associated with fungi which improve nutrient uptake, drought, and frost tolerance and protect the higher plants against pathogens. The fungi withdraw glucose from plant roots and act as a significant sink for carbohydrates. Mycorrhizae may also stimulate photosynthesis and thus strongly influence maintenance and competitiveness of plants. Dominik (1963) pointed out the significant influence of mycorrhizae on species composition in plant communities. Since then a body of information has been compiled confirming this early statement (see reviews by Trappe, 1988; Trappe and Luoma, 1992; Molina et al., 1992, Allen et al., 1997; Van der Heijden et al., 1998b).
