engleski

Guaiacol peroxidases and photosynthetic pigments in ageing spruce needles

Needles of coniferous trees are long living plant organs, existing for several years on the healthy trees where they are exposed to a variety of stressful influences. The aim of our study was to investigate changes in guaiacol peroxidases activity, electrophoretic pattern and photosynthetic pigments content in spruce needles of different ages. Four generations of needles (CY – current year ; 1-YO – one year old ; 2-YO – two years old ; 3-YO – three years old) were collected in July 2004, from the lower crown of ten Norway spruce trees. Needles were cut into small pieces and macerated in liquid nitrogen. Photosynthetic pigments were extracted with anhydrous acetone and quantified spectrophotometrically. Soluble proteins were extracted in ice-cold Tris-HCl buffer, pH=8.0. Enzyme activity was determined by measuring the absorbance increase at 470 nm, using guaiacol and H2O2 as substrates. The number of isoperoxidases was investigated by native PAGE. Total chlorophylls content was 1.02 mg/g FW (fresh weight) in CY, while the values were higher in older needles: 1.55, 1.55 and 1.56 mg/g FW in 1-YO, 2-YO and 3-YO, respectively. However, differences were observed in chlorophyll a to b ratio: 1.97 in CY, 1.90 in 1-YO, 1.81 in 2-YO and 2.29 in 3-YO. Total carotenoids content was the lowest in CY (0.15 mg/g FW) while the values in older needles were 0.23, 0.22 and 0.28 mg/g FW in samples 1-YO, 2-YO and 3-YO, respectively. Peroxidase activity measurement revealed the increase of the activity with the needles age. The lowest value was in CY (0.05 ∆ A_470 min-1 mg-1 FW), and the values in older needles were: 0.10, 0.15 and 0.17 ∆ A_470 min-1 mg-1 FW in 1-YO, 2-YO and 3-YO, respectively. Electrophoretic analysis revealed differences in isoperoxidase pattern as well as in the intensity of the individual bands. Differences were pronounced between the current-year and older needles. It can be concluded that spruce needles changed their biochemical and molecular properties during ageing. Increase in photosynthetic pigments content was the most pronounced during the first year of development. The expression of new isoperoxidases was also observed in the same period, while the total peroxidase activity was increasing continuously during needles ageing.

Guaiacol peroxidases; photosynthetic pigments; ageing needles; Picea abies

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