PHOTOINHIBITION OF PHOTOPHOSPHORYLATION, ADENOSINE-TRIPHOSPHATE CONTENT, AND GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE (NADP-IRRADIANCE DESICCATION OF SELAGINELLA-LEPIDOPHYLLA() FOLLOWING HIGH)

Selaginella lepidophylla (Hook. and Grev.) Spring, a poikilohydrous de sert 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 reduc tion of light-activated enzyme activities, noncyclic photophosphorylat ion, and adenosine triphosphate content was tested under laboratory co nditions. Plants restrained from curling during desiccation at a const ant irradiance of 2000-mu-mol . m-2 . s-1 when rehydrated had signific antly decreased glyceraldehyde-3-phosphate dehydrogenase (NADP+) enzym e 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 dehy drogenase enzyme activities were not significantly affected by the res traint treatment. These results demonstrate that stem curling during d esiccation limits bright-light damage that could otherwise decrease ph otophosphorylation capacity. adenosine triphosphate content, and light -activated carbon assimilation enzyme activity when the plants are nex t wetted. In addition, examination of the adenosine phosphate contents of desiccated, 24-h dark hydrated, and 24-h 500-mu-mol . m-2 . s-1 ir radiance hydrated Selaginella lepidophylla plants revealed that adenos ine triphosphate pools were not conserved during desiccation and that during hydration in the light, adenosine triphosphate content increase s substantially as a result of both oxidative and photophosphorylation .