ENVIRONMENTAL STRESSES AND ANTIOXIDATIVE RESPONSES OF PINUS-CANARIENSIS AT DIFFERENT FIELD STANDS IN TENERIFE

In the present paper, we investigate antioxidants, chloroplast pigment s, ultrastructure, and chlorophyll fluorescence in needles of Pinus ca nariensis Chr. Sm. ex DC. collected at four natural stands covering an altitude range from 200 to 2000 m a. s. 1. in the South-East of Tener ife. The contents of chloroplast pigments were lower at the most eleva ted sites showing chlorophyll concentrations of about 1 mg g(-1) needl e dry weight (DW) versus 2 mg g(-1) DW at the lowest sites. Mean antio xidant concentrations in one year old needles were 260 to 200 mu g g(- 1) DW for alpha-tocopherol, 3 to 4.5 mg (-1) DW for ascorbic acid and 340 to 180 nmol g(-1) DW for glutathione. A strict altitude dependence of these parameters was not found. Chlorophyll fluorescence measureme nts revealed Fv/Fm above 0.75 for all sites indicating healthy photosy nthetic apparatus, but revealed initial states of oxidative stress at one particular site. Depressions in Fv/Fm went together with decreased alpha-carotene/beta-carotene ratios and a decrease in the ratio of vi olaxanthin to total xanthophyll cycle carotenoids. Ultrastructural inv estigations of the chloroplasts indicated no severe damage to the thyl akoid systems.