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The stems of the resurrection plant Selaginella lepidophylla, a poikilohydrous desert pteridophyte, curl dramatically as the plants dry and uncurl when rewetted. We tested the hypothesis that stem curling is a morphological feature that may serve to limit bright-light and/or thermal damage in resurrection plants with a field experiment at a Chihuahuan desert site in west Texas. Experimental plants were irrigated for 3 d and then permitted to dry. The plants were either allowed to curl normally or mechanically restrained to prevent curling and either shaded (10% of ambient irradiance) or left fully exposed during desiccation. Nine days after complete desiccation, the plants were harvested and returned to the laboratory. When rehydrated, plants that had been unshaded and restrained from curling during field desiccation had significantly lower photosystem II electron transport rates, higher intrinsic chlorophyll fluorescence (F0) yields, lower variable to maximum chlorophyll fluorescence (F(v)/F(m)) yield ratios, lower chlorophyll contents, and both lower whole-plant photosynthetic quantum efficiencies and light-saturated CO2 assimilation rates relative to plants from the other desiccation treatments. The results of both low-irradiance and high-irradiance hydrations in the laboratory suggest that the curling during desiccation and the uncurling during rehydration of S. lepidophylla in its natural habitat serves to protect the plant from damage due to high irradiance, high temperature, or perhaps a synergistic combination of the two. This protection permits the rapid recovery of photosynthetic competence when next the plants are wetted, thereby helping to maximize net carbon balance over time.