© 2004 Heron Publishing—Victoria, Canada
Drought-induced changes in flavonoids and other low molecular weight antioxidants in Cistus clusii grown under Mediterranean field conditions
Iker Hernández (1), Leonor Alegre (1) and Sergi Munné-Bosch (1, 2)
1. Departament de Biologia Vegetal, Facultat de Biologia, Universitat de Barcelona, Avinguda Diagonal 645, E-08028 Barcelona,
Spain / 2. Corresponding author (smunne@ub.edu) / Received October 24, 2003; accepted April 30, 2004; published online September 1, 2004
Summary
Mediterranean plants have evolved a complex antioxidant defense system to cope with summer drought. Flavonoids, and particularly
flavanols and flavonols, are potent in vitro antioxidants, but their in vivo significance within the complex network of antioxidant
defenses remains unclear, especially in plant responses to stress. To gain insight into the role of flavonoids in the antioxidant
defense system of Cistus clusii Dunal, we evaluated drought-induced changes in flavonoids in leaves and compared the response of these compounds with that
of other low molecular weight antioxidants (ascorbic acid, tocopherols and carotenoids). Among the antioxidant flavonoids
analyzed, epigallocatechin gallate was present in the greatest concentrations (up to about 5 µmol dm–2). Other flavanols, such as epicatechin and epicatechin gallate, were found at concentrations below 0.25 and 0.03 µmol dm–2, respectively. Neither of the antioxidant flavonols analyzed, quercetin and kaempferol, were detected in C. clusii leaves. Epigallocatechin gallate, ascorbic acid and α-tocopherol concentrations increased to a similar extent (up to 2.8-,
2.6- and 3.3-fold, respectively) in response to drought, but the kinetics of the drought-induced increases differed. Epigallocatechin
gallate, epicatechin and epicatechin gallate concentrations increased progressively during drought, reaching maximum values
after 30 days of stress. Ascorbic acid concentrations increased twofold after 15 days of drought, and maximum values were
attained after 50 days of drought. In contrast, α-tocopherol concentrations remained constant during the first 30 days of
drought, but increased sharply by 3.3-fold after 50 days of drought. The maximum efficiency of photosystem II photochemistry
and the extent of lipid peroxidation remained constant throughout the drought period, whereas the redox state of ascorbic
acid and α-tocopherol shifted toward their reduced forms in response to drought, indicating that the concerted action of low
molecular weight antioxidants may help prevent oxidative damage in plants.
Keywords:
ascorbic acid, carotenoids, flavanols, oxidative stress, tocopherols.
