Rosa Elia Magaña-Lemus, Irene Ávila-Díaz, Roberto Garibay-Orijel
Background and Aims: Mycorrhizal symbiosis is important for orchids during early stages of development. This association in subsequent developmental stages is scarcely documented, specifically in epiphytic orchids. The objective of this work was to evaluate the mycorrhization of Rhynchostele cervantesii in two developmental stages under contrasting weather conditions. Methods: The mycorrhization was evaluated in situ in 50 adult plants and 50 juvenile plants during wet and dry seasons for two years. We collected one or two roots per plant. The mycorrhization percentage was registered, and digestion state of pelotons as: a) intact, b) digestion process and c) digested. The type of root attachment was registered as in contact with the substrate or aerial, and the root zone as basal, medium and apical. Key results: The average mycorrhization percentage between juvenile and adult plants was not significantly different, while between seasons, it was higher in wet season 1, followed by wet season 2. The lowest percentages of mycorrhization were registered for dry seasons 1 and 2. Intact peloton average during average wet season (18 pelotons) was significantly higher than in the dry season (0.5 pelotons), while digested pelotons were more abundant in dry season (10.5 pelotons) than in the wet season (0.5 pelotons), with no differences between juvenile and adult plants. Mycorrhization percentage was significantly higher in roots in contact with substrate (32%) than in aerial roots (28%), and higher in basal roots (55%) than in apical roots (2%). Conclusions: Functional mycorrhization (with degraded pelotons) is present in two orchid developmental stages, suggesting that this association is important during the complete life cycle of R. cervantesii. Dry season negatively impacts the mycorrhization percentage and positively the digestion of pelotons. Therefore, we consider that the prevalence of droughts could have an adverse effect on this association.