STUDIES ON THE ALTERATIONS IN PHOTOSYNTHETIC ELECTRON TRANSPORT AND SPECTRAL PROPERTIES OF THE CYANOBACTERIUM, SPIRULINA PLATENSIS UNDER COPPER STRESS Rajya Lakshmi.C, Jyothsna,P. and Murthy, S.D.S

ABSTRACT: Spirulina platensis is a filamentous and photosynthetic blue green algae. Heavy metals are toxic when their levels in the environment exceed. They cause damage to living organisms including plants. Prolonged incubation (48 h) of Spirulina platensis cells in the presence of copper (Cu) (20 and 80 μM) caused inhibition of Photosystem (PS) II catalyzed electron transport activity (H2O→pBQ). The loss observed by 50% in PS II catalysed electron transport at 60μM. At this concentration it also alters the absorption spectra of Spirulina platensis. The inhibition at PS II could be due to either alterations at the water oxidation complex or changes in light harvesting complex. Unlike PSII, PSI catalysed electron transport (DCPIPH→MV) is less sensitive to Cu treatment. This loss in PSI catalysed electron transport could be due to alterations in the PSI reaction centre. Thus Cu affects both PSII and PSI in preferential manner.