Photosynthetic recovery of resurrection spikemosses from different hydration regimes

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Abstract
Patterns and mechanisms of recovery of photosynthetic activity of two resurrection spikemoss species from different hydration environments in the Chihuahuan desert of southwest Texas, USA were compared in the laboratory. Selaginella lepidophylla Hook. and Grev. is the dominant poikilohydric plant found in hot, arid low-elevation desert scrub communities and S. pilifera A. Br. is one of many poikilohydric species found in more mesic, high-elevation woodland communities in Big Bend National Park, Texas. Infrared gas analysis of CO2 exchange during hydration of desiccated plants indicated that photosynthetic competence was achieved significantly more rapidly in S. lepidophylla tha S. pilifera. Chloramphenicol, a chloroplast protein synthesis inhibitor at 100 μg·ml-1 in the hydration medium, significantly inhibited the resumption of CO2 uptake in both species, but the level of inhibition was significantly greater in S. pilifera. The level of conserved ribulose 1,5 bis phosphate carboxylase specific activity in desiccated plants was significantly greater in S. lepidophylla. These results support the hypothesis that poikilohydric plants from increasingly xeric environments are capable of more rapid photosynthetic recovery, due to increased conservation of the photosynthetic system during desiccation and a reduced requirement for photosynthetic system repair during hydration, than those from more mesic environments.