Photosynthetic recovery of the resurrection plant Selaginella lepidophylla (Hook. and Grev.) Spring: effects of prior desiccation rate and mechanisms of desiccation damage

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Abstract
The effects of desiccation rate on photosynthetic recovery of the resurrection plant Selaginella lepidophylla (Hook. and Grev.) Spring were examined. Gas exchange over a 24 h rehydration period, ribulose bisphosphate carboxylase conservation in desiccated fronds, de novo protein synthesis rate during rehydration, and frond leakage rate during rehydration were measured following desiccation at various rates. Seven-day hydrated, fully recovered plants were dried at four rates. The initial decline in tissue fresh weight/dry weight ratio was essentially linear to a ratio value of 1.35, the point at which frond curling occurred, but slowed thereafter. Frond curling required 5.5, 52, 94, and 175 h of desiccation, respectively, for the four treatments. The rate of net photosynthesis after 24 h of rehydration was greatest for the two intermediate drying speeds; both very rapid and very slow drying were associated with significantly reduced rates. Electrolyte leakage was greatest following very rapid drying and de novo protein synthesis was impaired following very slow drying. Ribulose bisphosphate carboxylase conservation was not significantly affected by drying speed. These results support the hypothesis that desiccation injury is multicausal and that specific components of the photosynthetic recovery process respond differently to desiccation rate. However, in spite of these significant desiccation rate effects, overall photosynthetic recovery in S. lepidophylla appears to be relatively tolerant of widely varying rates of desiccation.