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

<p><strong>Background:</strong><em> Castilleja tenuiflora</em> is a hemiparasite of <em>Baccharis conferta</em>. 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.</p><p><strong>Question: </strong>What is the structure and anatomy of haustoria builded in field interaction? Based on C, N and chlorophyll contents, is <em>C. tenuiflora</em> a facultative hemiparasite of <em>B. conferta</em>?<strong></strong></p><p><strong>Species studied: </strong><em>Castilleja tenuiflora</em> Benth. and <em>Baccharis conferta</em> Kunth.<strong></strong></p><p><strong>Study site and dates:</strong> 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.<strong></strong></p><p><strong>Methods</strong>: Individuals of <em>B. conferta</em> and <em>C. tenuiflora </em>growing independently or in hemiparasite interactions were collected and samples were processed for anatomical and histochemical characterization, determination of C, N and chlorophyll.</p><p><strong>Results:</strong><em> </em>Haustoria were globular and located mainly in the lateral roots of <em>B. conferta</em>. Anatomy of haustorium shows the characteristic structures: exophyte and endophyte. Haustorial tissues storage starch, tannins and essential oils while in the <em>B. conferta</em> 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 <em>C. tenuiflora</em> and <em>B. conferta</em>.</p><strong>Conclusions:</strong><em> </em>Haustoria builded in interaction with <em>B. conferta</em> show the characteristic structure and anatomy. Hemiparasitic relationship represents for <em>C. tenuiflora</em> a source of C and other compounds such as essential oils.