Epiphytic and terrestrial mycorrhizas in a lower montane Costa Rican cloud forest

Abstract

The epiphyte community is the most diverse plant community in neotropical cloud forests and its collective biomass can exceed that of the terrestrial shrubs and herbs. However, little is known about the role of mycorrhizas in this community. We assessed the mycorrhizal status of epiphytic (Araceae, Clusiaceae, Ericaceae, and Piperaceae) and terrestrial (Clusiaceae, Ericaceae) plants in a lower montane cloud forest in Costa Rica. Arbuscular mycorrhizas were observed in taxa from Araceae and Clusiaceae; ericoid mycorrhizas were observed in ericaceous plants. This is the first report of intracellular hyphal coils characteristic of ericoid mycorrhizas in roots of Cavendishia melastomoides, Disterigma humboldtii, and Gaultheria erecta. Ericaceous roots were also covered by an intermittent hyphal mantle that penetrated between epidermal cells. Mantles, observed uniquely on ericaceous roots, were more abundant on terrestrial than on epiphytic roots. Mantle abundance was negatively correlated with gravimetric soil water content for epiphytic samples. Dark septate endophytic (DSE) fungi colonized roots of all four families. For the common epiphyte D. humboldtii, DSE structures were most abundant on samples collected from exposed microsites in the canopy. The presence of mycorrhizas in all epiphytes except Peperomia sp. suggests that inoculum levels and environmental conditions in the canopy of tropical cloud forests are generally conducive to the formation of mycorrhizas. These may impact nutrient and water dynamics in arboreal ecosystems.

Arbuscular mycorrhizal colonization in Asteraceae from white sand savannas, in Pinar del Río, Cuba

“…13,no. 3 occurrence of DSE and AMF and suggest that it is common in plant roots in nature (Rains et al 2003, Muthukumar et al 2006, SantosGonzalez et al 2007, Mandyam & Jumpponen 2008, Khidir et al 2010, Yang et al 2010) and some of them suggest that colonization of roots can be interfered by non-mycorrhizal endophytes, especially during the hot season which corresponds to the plant growing season when water availability is low and that a competition between both endophytes during colonization could limit the distribution of AM in dry region (Mandyam & Jumpponen 2008, Khidir et al 2010, Yang et al 2010. This relation has not been clarified yet; therefore, further studies are needed for resolving the existing relations between both fungal endophytes.…”

Variation in nitrogen use strategies and photosynthetic pathways among vascular epiphytes in the Brazilian Central Amazon

“…epiphytes have slower growth rates, accessory structures (e.g. trichomes and velamen), as well as association with insects and microorganisms (Nadkarni 1984, Stewart et al 1995, Kauff et al 2000, Rains et al 2003, Tsavkelova et al 2003, Shefferson et al 2005.…”

Influence of Habitat and Climate Variables on Arbuscular Mycorrhizal Fungus Community Distribution, as Revealed by a Case Study of Facultative Plant Epiphytism under Semiarid Conditions

“…The results of previous studies suggest that many plant species that are commonly mycorrhizal when they grow terrestrially are inconsistently mycorrhizal when they grow epiphytically (5,6). However, Rains et al (4) found abundant mycorrhizal structures on epiphytic roots indicating a significant mycorrhizal presence (arbuscular and ericoid mycorrhizas) in the canopy of a lower montane cloud forest in Costa Rica. In these previous studies, the morphology of structures in or around the root was used to characterize plants as mycorrhizal or nonmycorrhizal; however, morphology provides a limited resolution to the question of whether or not a plant species is mycorrhizal.…”

“…Some epiphytes have evolved adaptations that provide efficient access to and retention of nutrients, such as litter-trapping leaf arrangements, slow growth rates, absorbent trichomes, and mycorrhizas (3,4). The results of previous studies suggest that many plant species that are commonly mycorrhizal when they grow terrestrially are inconsistently mycorrhizal when they grow epiphytically (5,6).…”