© 2003 Heron Publishing—Victoria, Canada
Enhanced photo- and antioxidative protection, and hydrogen peroxide accumulation in drought-stressed Cistus clusii and Cistus albidus plants
Sergi Munné-Bosch (1), Tana Jubany-Marí (1) and Leonor Alegre (1, 2)
1. Departament de Biologia Vegetal, Facultat de Biologia, Universitat de Barcelona, Avinguda Diagonal 645, E-08028 Barcelona,
Spain / 2. Author to whom correspondence should be addressed (leonor@porthos.bio.ub.es) / Received January 30, 2002; accepted June 30, 2002; published online December 2, 2002
Summary
Mechanisms of drought stress resistance were studied in Cistus clusii Dunal and Cistus albidus L., two native Mediterranean shrubs that can withstand severe summer drought. While water deficit, solar radiation and temperature
increased from winter to summer in the field, C. clusii and C. albidus reduced leaf area, increased root mass per leaf area, and showed diurnal changes in stomatal conductance to minimize water
loss. In both species, the consequent reductions in CO2 assimilation were accompanied by reduced efficiency of photosystem II photochemistry, and protection against stress was afforded
by enhanced de-epoxidation of violaxanthin in the xanthophyll cycle and increases in α-tocopherol and β-carotene. In addition,
hydrogen peroxide (H2O2) accumulation was observed in mesophyll cell walls of both species during the first stages of drought, although no accumulation
of H2O2 was observed in chloroplasts or other organelles during the study. Despite these common responses, C. albidus and C. clusii differed in the extent of photo- and antioxidative protection. In response to drought, C. clusii showed a higher de-epoxidation state of the xanthophyll cycle and higher α-tocopherol and β-carotene concentrations than
C. albidus. We conclude that several structural and biochemical mechanisms underlie stress resistance in C. clusii and C. albidus, and are indicative of the different degrees of stress resistance of these shrubs.
Keywords:
antioxidants, oxidative stress, photoprotection, photosynthesis.
