Enhanced Formation of alpha-Tocopherol and Highly Oxidized Abietane Diterpenes in Water-Stressed Rosemary Plants.
The lipid-soluble antioxidants alpha-tocopherol and carnosic acid were studied in field-grown rosemary (Rosmarinus officinalis L.) plants subjected to drought. During summer in the Mediterranean region, the predawn water potential decreased to -3 MPa and the relative water content to 42%, which caused a depletion of the maximum diurnal CO(2) assimilation rate by 80%. Meanwhile, the maximum efficiency of photosystem II photochemistry and the chlorophyll content of leaves remained unaltered, indicative of the absence of photooxidative damage. The concentration of alpha-tocopherol increased by 15-fold and that of carotenoids by approximately 26% in response to water stress. Enhanced formation of the highly oxidized abietane diterpenes isorosmanol (by 25%) and dimethyl isorosmanol (by 40%) was observed during the summer as result of the oxidation of carnosic acid, which decreased by 22%. The large amounts of carnosic acid, alpha-tocopherol, and carotenoids present in rosemary leaves might contribute to the prevention of oxidative damage in plants exposed to drought.
Munné-Bosch
S
Departament de Biologia Vegetal, Facultat de Biologia, Universitat de Barcelona, Avinguda Diagonal 645, 08028 Barcelona, Spain.
Schwarz
K
Alegre
L