The correlation between high-temperature and desiccation tolerances in a poikilohydric desert plant

The high-temperature tolerance of the desiccation-tolerant pteridophyte Selaginella lepidophylla (Hook. & Grev.) Spring was examined under laboratory conditions. Both desiccated whole plants and detached fronds were stored at 25, 45, and 65 °C for 1 to 70 days. The effects of high-temperature storage on whole plant photosynthetic recovery, conservation of ribulose 1,5-bisphosphate (RuBP) carboxylase in desiccated fronds, apparent membrane damage as measured by frond leakage of electrolytic and UV-absorbing materials upon rehydration, and protein synthesis upon rehydration of detached fronds were determined. The temperature dependence of net photosynthesis of fully recovered, hydrated plants was also described. Desiccated storage for 17 days at 45 °C significantly impaired whole-plant photosynthetic recovery, and conservation of RuBP carboxylase in desiccated fronds declined within 33 days of storage at 45 °C, both relative to 25 °C controls. Storage at 65 °C caused additional inhibition of both photosynthetic recovery (after 17 and 33 days) and RuBP carboxylase conservation (within 70 days) over that for 45 °C storage. Frond leakage was significantly increased and protein synthesis was significantly reduced after 65 °C storage for 7 and 33 days, respectively, relative to controls. These results suggest that desiccation tolerance and high-temperature tolerance are not highly correlated in S. lepidophylla, which is more sensitive to high-temperature conditions when both hydrated and desiccated than was initially expected for a poikilohydric desert pteridophyte.