CHANGES OF FLUORESCENCE AND XANTHOPHYLL PIGMENTS DURING DEHYDRATION IN THE RESURRECTION PLANT SELAGINELLA-LEPIDOPHYLLA IN LOW AND MEDIUM LIGHT INTENSITIES

The changes in photosynthetic efficiency and photosynthetic pigments d uring dehydration of the resurrection plant Selaginella lepidophylla ( from the Chiuhahuan desert, S.W. Texas, USA) were examined under diffe rent light conditions. Changes in the photosynthetic efficiency were d educed from chlorophyll a fluorescence measurements (F(o), F(m), and F (v)) and pigment changes were measured by HPLC analysis. A small decre ase in F(v)/F(m) was seen in hydrated stems in high light (650 mumol p hotons . m-2 . s-1) but not in low light (50 mumol photons . m-2 . s-1 ). However, a pronounced decline in F(v)/F(m) was observed during dehy dration in both light treatments. after one to two hours of dehydratio n. A rise in F(o) was observed only after six to ten hours of dehydrat ion. Concomitant with the decrease in photosynthetic efficiency during dehydration a rise in the xanthophyll zeaxanthin was observed, even i n low-light treatments. The increase in zeaxanthin can be related to p reviously observed photoprotective non-photochemical quenching of fluo rescence in dehydrating stems of S. lepidophylla. We hypothesize that under dehydrating conditions even low light levels become excessive an d zeaxanthin-related photoprotection is engaged. We speculate that the se processes, as well as stem curling and self shading (Eickmeier et a l. 1992) serve to minimize photoinhibitory damage to S. lepidophylla d uring the process of dehydration.