The effect of pH on in vitro growth of protonemata, asexual propagules, or gametophytes fragments of four Neotropical moss species

Many abiotic factors affect bryophyte survival. Ecosystem’s abiotic factors have been altered by anthropogenic disturbance and this has taken a toll in bryophyte species diversity. Bryophyte in situ or ex situ culture can be used to assess how these abiotic factors affect plant growth, restoration, and conservation of endangered species. For Neotropical species, it is poorly understood how an ex situ technique like in vitro culture may affect these plants. In addition, information regarding how pH can affect these species is lacking; especially when the medium pH is a factor that can influence germination and differentiation of spore, asexual propagules, protonemata or gametophyte modules. Therefore, the effect of media pH on gametophyte modules (Neckeropsis disticha), spores (Octoblepharum albidum and Vesicularia vesicularis var. vesicularis), and asexual propagules (Calymperes afzelii) were studied to observe species requirements for optimal module growth. Sterile bryophyte modules were inoculated into petri dishes that contained different pH treatments (pH 4, 5, 6; multiple pH values in the range 4-5 and 5-6) and MS medium. Variation in plant modules growth (length) and survival were annotated, as well compared among pH treatments for each species. Species demonstrated various patterns of module growth, according to treatments. Among these, N. disticha's fragmented gametophytes growth varied. C. afzelii grew best at pH 6.0, while O. albidum optimal growth was at pH 5.0. Vesicularia vesicularis var. vesicularis protonemata grew best when pH was decreased (4.0). The decrease/increase of pH may or not alter growth patterns; this will depend on the species requirement/tolerance for a range/niche of pH. Furthermore, this study showed that the frequently used pH 5.8 is not necessarily required for these Neotropical species and therefore culture methods should be revised when propagating bryophyte species; especially when studying threatened species.