Envi~onmentalandE~petimentatBotal~y, Vol. 32. N,~. 2, pp. 137 143, ltlt92 I)098 8472i92 $5.00+0.00 Printed in (;real Britain. Pergamon Press ph EFFECTS OF SUPPLEMENTAL U.V.-B RADIATION ON PHOTOSYNTHETIC PIGMENT, PROTEIN AND GLUTATHIONE CONTENTS IN GREEN ALGAE S. B. AGRAWAL Centre of Advanced Study in Botany, Banaras Hindu University, Varanasi-221 005, India (Received 17 June 1991 ; accepted in revised form 21 October 1991 ) A6RAWAL S. B. Effects of supplemental u.v.-B radiation on photosynthetic p~rnent, protein and glutathione contents in green algae. ENVIRONMENTAL AND EXPERIMENTALBOTANY32, 137-143, 1992. Growth chamber experiments were conducted to investigate the effects of supplemental u.v.-B radiation (280 320 nm) on chlorophyll, carotenoid, protein and glutathione contents in two green algae, Chlorococcum infusionum (Schrank) Meneghini (Chlorococcales) and Chlorogonium elongatum (Dang.) France (Volvoeales). U.v.-B exposure reduced chlorophyll, carotenoid and protein contents. The reduction in chlorophyll a content was higher than that of chlorophyll b. There were significant increases in cellular concentrations of total, reduced (GSH) and oxidized (GSSG) glutathione following u.v.-B treatment. However, the GSH/GSSG ratio was lower in u.v.-B exposed algae. Chlorogonium was found to be more responsive to supplemental u.v.-B exposure as compared to Chlorococcum. Variations in oxidized and reduced glutathione fractions due to supplemental levels of u.v.-B correlated with the response pattern of the algae. Key words: Green algae, Chlorococcum, Chlorogonium, u.v.-B, photosynthetic pigment, protein, glutathione. INTRODUCTION SEVERAL anthropogenic human activities have increased the release of halogenated hydro- carbons and many trace gases in the atmosphere, which have been found to be responsible for depletion of the stratospheric ozone layer] 2~/Such depletions have led to increases at the earth's surface of solar ultraviolet-B radiation (u.v.-B, 290-320 nm), which can damage biological systems. '2t Numerous studies have been con- ducted on the effects of enhanced u.v.-B levels on plant growth and physiological and biochemical processes. 1'5'21) Ambient solar u.v.-B can pen- etrate deep into the photic zone of water columns and damage planktonic organisms. (37/ Biomass production near surface water was reduced due to solar u.v.-B irradiation? 18'36/U.v.-B stress also affected motility, community composition, pig- mentation, and several metabolic processes of algal systems. (7'8'15'24i Plant cells contain considerable amounts of free, low molecular weight thiol as glutathione (7- L-glutamyl-L cysteinyl glycine). 2ai Reduced glu- tathione (GSH) has been shown to be involved in many functions within the cell, including regu- lation of protein and DNA synthesis and as an essential cofactor tbr many enzymes. ~'~'27! Glu- tathione also plays an important role in resistance mechanisms by scavenging free radicals and thus protecting photosynthetically active plant cells against several toxic oxygen-derived chemical species./2i No work is available on the role ofglu- tathione in reducing adverse effects of sup- plemental u.v.-B radiation on an algal system. The present study was conducted to evaluate 137