Photoinhibition of photophosphorylation, adenosine triphosphate content, and glyceraldehyde-3-phosphate dehydrogenase (NADP+) following high-irradiance desiccation of Selaginella lepidophylla

Abstract

Selaginella lepidophylla (Hook, and Grev.) Spring, a poikilohydrous desert pteridophyte, curls dramatically during desiccation. As part of a larger study of potential photoinhibition in this resurrection plant, the hypothesis that stem curling may ameliorate high-irradiance reduction of light-activated enzyme activities, noncyclic photophosphorylation, and adenosine triphosphate content was tested under laboratory conditions. Plants restrained from curling during desiccation at a constant irradiance of 2000 μmol ∙ m−2 ∙ s−1 when rehydrated had significantly decreased glyceraldehyde-3-phosphate dehydrogenase (NADP+) enzyme activity, noncyclic photophosphorylation, and adenosine triphosphate content relative to plants that were allowed to curl naturally under the same conditions. Ribulose bisphosphate carboxylase and malate dehydrogenase enzyme activities were not significantly affected by the restraint treatment. These results demonstrate that stem curling during desiccation limits bright-light damage that could otherwise decrease photophosphorylation capacity, adenosine triphosphate content, and light-activated carbon assimilation enzyme activity when the plants are next wetted. In addition, examination of the adenosine phosphate contents of desiccated, 24-h dark hydrated, and 24-h 500 μmol ∙ m−2 ∙ s−1 irradiance hydrated Selaginella lepidophylla plants revealed that adenosine triphosphate pools were not conserved during desiccation and that during hydration in the light, adenosine triphosphate content increases substantially as a result of both oxidative and photophosphorylation. Key words: Selaginella lepidophylla, photoinhibition, desiccation tolerance, photophosphorylation, adenosine phosphate.