Photosynthetic Activities of a Roof-Top Desiccation Tolerant Cyanobacterium Scytonema geitleri at Varying Hydration Levels

Algae > Volume 16(4); 2001 > Article

Algae 2001;16(4): 445-455.

S.N. Tripathi, J.N. Maurya

Department of Botany, Banaras Hindu University, Department of Plant Sciences, Faculty of Applied Sciences, M.J.P. Rohilkhand University

ABSTRACT

Photosynthetic activities of a diazotrophic desiccation tolerant cyanobacterium Scytonema geitleri growing on roof-tops of buildings of the University campus were studied by monitoring 14C-fixation, O₂ evolution/consumption, DCPIP photoreduction and chlorophyll fluorescence (Fv/Fm) behaviour at various durations and levels of hydration of dry and growing mats. 0 MPa osmotic water potential has been found most favourable for recovery of these photosynthetic parameters on rehydration of dry mats, where Fv/Fm recovered faster than electron transports. 14C-fixation took maximum time in recovery on rehydration. 24h incubation at 0 MPa osmotic water potential under growing conditions was found most favourable for maximum recovery in these parameters. Thylakoids isolated from dry mats when grown at different osmotic water potentials (including 0 MPa) maintained by different sucrose solutions showed more recovery of PS I, than PS II and whole chain electron transports. Matric treatment was found less effective than osmotic water potential during rehydration. On dehydration, all those parameters, excepting Fv/Fm, which showed faster recovery on rehydration, were found more sensitive to lowering of matric water potentials. Hydroxylamine (NH₂OH) and diphenyl carbazide (DPC) treatments have reflected about repairable changes in the PS II during dehydration.

Key words: carbon fixation, chlorophyll fluorescence, cyanobacteria, desiccation, photosynthetic electron transports, water analogs