Abstract:
Vascular epiphytes call be quite abundant in vegetation close to the ocean surf. where they are exposed to a more or less Continuous input of salt spray. The ecophysiological basis of their Occurrence, i.e. salt tolerance or avoidance is Unresolved. because all previous Studies were observational and conclusions thus circumstantial. Here. the effect of varying concentrations of salt water on germination. and growth and survival of seedlings and established plants was investigated in a growth cabinet study under controlled conditions. Seeds (1500). seedlings (750) and small tank plants (336) were front four populations of Werauhia sanguinolenta that were growing either close to the sea or inland in Panama. Changes of Na+ and K+ concentrations in plant tissue were also determined. No differenccs in the sensitivity to salt were found among populations. nor among life stages. External concentrations (C-ext) of up to 15% sea water (c. 0.5% Na+) allowed complete germination as well as positive growth and survival in both seedlings and established plants over short periods (8-10 wk). After longer exposure ( 12 wk) of established plants visible damage and increased mortality were observed at lower C-ext, but critical tissue Na+ levels were similar: c. 50 mg gDW(-1). It is concluded that this Common epiphyte does not meet. the definition of a halophyte. but still possesses a rather high tolerance to sodium.
