ANATOMOCAL RELATIONS AMONG ENDOPHYTIC HOLOPARASITIC ANGIOSPERMS, AUTOTROPHIC HOST PLANTS AND MYCORRHIZAL FUNGI: A NOVEL TRIPATITE INTERACTION1.

Mycorrhizae are widespread mutualistic symbioses crucial for the functioning of terrestial ecosystems. Not all plants associate with mycorrhizae; most parasitic plants have been siggested to be nonmycorrhizal because they have developed alterantive strategies to obtain nutrients. In endophytiv parasitic plants, whose vegetative bodies grow completely inside their mycorrhizal host roots, the opportunity for establishing a tripartite association seems evident, but information on these systems is lacking. In studying natural associationc among hte endophytic holoparasite Cytinud hypocistis, their Cistaceae host species, and associated mycorhizal fungi, we found that mycorrhizae were associated wiht the hosts and the parasires, reaching high frequencies of colonization. In parasitic and host root tissues, mycorrhizal fungi spread in the parenchymatic cells by intracellular growth and formed hyphal coils and vesicles, while the cambium and the vascular tissues were never colonized. This report is the first on a tripatite association of an endophytic parasitic plant, its host, and nycorrhizae in natural conditions, representing a novel trophic interaction not previously reported within the angiosperms. Additional studies on the interactions occuring among these three players are needed because they may be crucial to our understanding of how this mutualistic – antagonistic system is functioning and evolving. [ABSTRACT FROM AUTHOR]