Seasonal changes in physiological and biochemical parameters were studied in 35-, 55- and 140-year-old trees of Turkey oak (Quercus cerris L.) and Hungarian oak (Q. frainetto Ten.), growing in natural stands in Eastern Balkan Mountains (Bulgaria). During the seasonal drought period (August), assimilation activity, transpiration rate, stomatal conductance and water potential had a seasonal minimum in all the studied tree ages and species. The foliar concentrations of glutathione, ascorbate, α-tocopherol, as well as photosynthetic pigments in oak leaves were significantly affected by season. With the increasing age of the studied trees, we observed a decrease of the physiological activity and an increase of the antioxidants’ accumulation. Both the species were drought tolerant and anisohydric, where Q. frainetto exhibited higher rates of gas exchange than Q. cerris. Moreover, they differed in the extent of increase in the foliar antioxidants and carotenoids.

ZELENA E., ZELENY F, WONISCH A. & TAUSZ M. 2011. Effect of sulfur nutrition on glutathione content in sugar beet plants in relation with aphids infestation. Phyton (Horn, Austria) 50 (2): 319-327, with 3 figures. The effects of sulfur (S) supply combined with nitrogen (N) on plant growth and biosynthesis of glutathione (GSH) in relation with aphids infestation were studied in young sugar beet (Beta vulgaris) plants infested with black bean aphids (Aphis fabae). Both nutrients applied separately stimulated growth of leaves but their effects were amplified when applied together. Single N fertilization enhanced significantly reproduction of aphids, addition of S reduced this effect to about 30 %. The contents of GSH in leaves on variants without S were very low (about 5 nmol/g FW) and manifold increased when S was added (up to about 550 nmol/g FW in middle youngest leaves). Sulfur supplied plants had about 5 times more GSH in youngest leaves than in oldest. The positive effect of S on resistance of plants to aphids manifested itself only in sugar beet supplied with N. We suspect GSH may function in prevention of toxic saliva action of aphids on metabolism of nitrogen in host plant and thus influence the quality of their food.

Biochemical measurements of antioxidants and protective pigments have been successfully introduced as markers of environmental stress in field studies (mainly forest studies). A guideline for field sampling and analysis methods is required to allow better comparison of data from different studies. The present review paper recommends HPLC methods for the analysis of ascorbate and glutathione (in oxidized and reduced form), tocopherols, and chloroplast pigments. Methodological variations are substantially lower (coefficients of variance of repeated extractions typically 4-9%) than biological variations of field samples (typical variation coefficients 8-36%), hence special emphasis is put on considerations of sampling standardization in the field with respect to sample time (seasonal and diurnal) and representative sampling of individuals and tissues. Following the suggestions in this paper would enable researchers to produce results that could be compared with those of several forest studies on conifers published in recent years. A larger data-set available for multivariate statistical evaluations (e.g. principal component analysis and cluster analysis) will enhance the diagnostic value of such investigations.

Three year old spruce trees (Picea omorika) were exposed to 100 and 225 nl l -1 SO 2 and H 2 S for three weeks. The number of chromosomal aberrations and the mitotic index in the root tip meristems, and glutathione and cysteine contents in fine roots were determined twice weekly. An increase in glutathione content in fine roots of H 2 S exposed plants was only detectable after 13 days of fumigation. The number of chromosomal aberrations increased significantly after 9 days of exposure to 225 nl l -1 H 2 S and after 13 days of exposure to 225 nl l -1 SO 2 or 100 nl l -1 H 2 S. This increase in chromosomal damage persisted up to the end of the 3 week treatment. Neither SO 2 nor H 2 S exposure affected the cysteine content or the redox state of glutathione in fine roots. These results suggest that the development of chromosomal aberrations during SO 2 and H 2 S exposures does not directly reflect changes in thiol/glutathione content or redox state in the fine roots.