Differential Effects of Desiccation on Hornworts with Contrasting Life Histories in Tropical Montane Forests: A Functional Trait—Based Perspective

Abstract

Desiccation tolerance (DT) is the ability of an organism or structure to dry completely and subsequently survive in that air-dry state. Hornworts are excellent plant models to study desiccation effects as they have contrasting life histories which are likely associated with DT. We tested whether (1) epiphytic species had more efficient DT responses to drying and postrehydration than non-epiphytic species and whether (2) “green” spores were more sensitive than non-green spores to extreme drying. Hornwort species were collected from the Atlantic Forest of Rio de Janeiro, Brazil. We studied five species (gametophytes and spores: Dendroceros crispus, D. crispatus, Nothoceros vincentianus, Phaeoceros carolinianus; and only spores of Anthoceros lamellatus), using different relative humidity values, drying durations, and postrehydration conditions. All DT treatments affected the chlorophyll fluorescence (Fv/Fm) of gametophytes, with species-specific responses. D. crispatus and D. crispus (epiphytes) performed better than P. carolinianus and N. vincentianus, with fast recovery of Fv/Fm values postrehydration. The ability of non-green spores of P. carolinianus and A. lamellatus and green spores of D. crispus to support desiccation led us to reject our second hypothesis. The DT strategies of hornworts highlighted the trade-offs that are important in spore dispersal and plant establishment, such as fast colonization in Dendroceros spp. and potential spore soil banks in Phaeoceros and Anthoceros species.