No effect of host tree species on the physiology of the epiphytic orchid Bulbophyllum japonicum in a subtropical rainforest in northeastern Taiwan

Chlorophyll concentrations, Crassulacean acid metabolism (CAM) acid fluctuations, and chlorophyll fluorescence parameters were measured in individuals of the epiphytic orchid Bulbophyllum japonicum growing on 3 different host tree species in a subtropical rainforest in northeastern Taiwan. No differences in any of the physiological measures were found. Thus, although the host tree species vary considerably in leaf morphology, bark characteristics, and elemental composition of stemflow water, such differences did not substantially impact the physiology of this epiphytic orchid. These results may reflect the slow growth rates and minimal nutrient requirements of this slow-growing, shade-adapted orchid. The findings of this study help explain the lack of host specificity in this epiphyte and perhaps in many other species.