Hemiparasitic interaction between Castilleja tenuiflora (Orobanchaceae) and Baccharis conferta (Asteraceae): haustorium anatomy and C- and N-fluxes

Abstract

Background: Castilleja tenuiflora is a hemiparasite of Baccharis conferta . The haustorium is the characteristic structure of hemiparasitic plants and its anatomy varies depending several factors such as host species, position on the root and environment. Question: What is the structure and anatomy of haustoria builded in field interaction? Based on C, N and chlorophyll contents, is C. tenuiflora a facultative hemiparasite of B. conferta ? Species studied: Castilleja tenuiflora Benth. and Baccharis conferta Kunth. Study site and dates: Plant materials were collected in the Iztaccihuatl-Popocatepetl National Park (N 19° 0.5´ 9.6 , W 98° 40´ 24.2 , 3,480 m.a.s.l.), State of Mexico, Mexico, in December 2013. Methods : Individuals of B. conferta and C. tenuiflora growing independently or in hemiparasite interactions were collected and samples were processed for anatomical and histochemical characterization, determination of C, N and chlorophyll. Results: Haustoria were globular and located mainly in the lateral roots of B. conferta . Anatomy of haustorium shows the characteristic structures: exophyte and endophyte. Haustorial tissues storage starch, tannins and essential oils while in the B. conferta roots also calcium oxalate crystals were found. C levels were significantly influenced by hemiparasitic interaction. This is the first study that characterizes a hemiparasitic interaction in the field and specifically between C. tenuiflora and B. conferta . Conclusions: Haustoria builded in interaction with B. conferta show the characteristic structure and anatomy. Hemiparasitic relationship represents for C. tenuiflora a source of C and other compounds such as essential oils.