Handbook of Vitamin C Research

(mgg -1 )320Samar Al Sayegh Petkovšek and Boštjan Pokornyunit of the ŠTPP in February 1995, it is most likely that after a long lasting stress in 1980‘sand 1990‘s the defence mechanism in spruce needles has started repairing and the normalmechanism of formation of antioxidant has been re-establishing after the implantation of thismitigation measure. After the second significantly reduction of emissions of SO 2 (after theinstallation of the desulphurization devices on the fifth unit of the ŠTPP in November 2000)the contents of vitamin C drastically diminished and remained almost equal.In order to assess the health status of investigated trees we also measured thephotosynthetic pigments, since oxidative stress tends to reduce chlorophyll content,especially chlorophyll a. The mean annual concentrations of total chlorophyll (a + b) incurrent-year needles are shown in Figure 3. A trend of increasing spruce vitality after 1995was confirmed; moreover, the chlorophyll content exceeded the limit value (1.5 mg/g – valueindicating tree injury) (Köstner et al., 1990) for the first time in that year and remained abovethis value until 2007 (with slightly decrease in year 1996, 1997 and 2002). Presumably,decrease of the total pigment contents in these three years were not correlated with airpollution, since emissions of air pollutants remained unchanged in that period. A lowervitality of trees (i.e. lower contents of pigment) in these three years reflects the impact ofnatural stressors (e.g. high summer T and drought in year 1996 and 2002, respectively).TOTAL CHLOROPHYLL (a + b)3,503,002,502,001,991,362,691,751,84 2,46 1,481,702,182,091,821,591,501,001,000,820,801,050,500,001991 1992 1993 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007Figure 3. Mean annual concentration of total chlorophyll (a + b) in current-year needles of sprucelocated in the emission area of ŠTPP. The horizontal line represents the limit value (1.5 mg/g). Thearrows marked the years in which desulphurization devices were installed (Unit 4 in February 1995 andUnit 5 in November 2000, respectively).3.2. Correlation AnalysisSince content of vitamin C in spruce needles, may be affected either by natural stressors(extreme temperatures, drought, ultraviolet radiation, etc.) or by air pollution, we tested theexistence of correlation between two stress-inducing factors (altitude and deposition of SO 2at selected locations) and mean annual content of vitamin C in spruce needles. Due to