Salinity, pH and temperature growth ranges of Halophytophthora isolates suggest their physiological adaptations to mangrove environments

摘要

Species of Halophytophthora are early colonisers of fallen mangrove leaves in the tropics butrecently found commonly in temperate areas. In mangrove habitats, temperature and salinitychange rapidly daily (high/low tide) and seasonally (summer/winter, rainy/dry seasons). Mangroveorganisms have to develop adaptive strategies to thrive in such a physiologically challengingenvironment. In this study, growth of three isolates of Halophytophthora avicenniae and twoisolates of H. batemanensis was tested under combined effects of 3 temperatures (15°C, 25°C, 37°C), 3 pHs (6, 7, 8) and 4 salinities (4 ‰, 8 ‰, 16 ‰, 32 ‰). No/little growth was observed at 37°Cand growth saturation occurred earlier at 25°C than at 15°C. The log phase of growth was steeperat pH 6 than pH 7 and 8. Temperature and pH were found to exert a greater effect on growth thansalinity. Generally, a reduction of growth rate was observed at pH 8 and 15°C. Increase in salinitycaused a slight decrease in growth, most noticeable at 32 ‰. The wide growth ranges oftemperature, salinity and pH of Halophytophthora isolates suggest that they are well adapted tothe physical and chemical conditions of mangrove habitats.