Az Eszterházy Károly Tanárképző Főiskola Tudományos Közleményei. 2004. Sectio Biologiae. (Acta Academiae Paedagogicae Agriensis : Nova series ; Tom. 25)
Makrai, L., Dulai, S., Polyánka, H., Ertli, T. and Lehoczki, E.: Monitoring of the Functional State of Beds of Common Reed (Phragmites australis) in Shallow Lake Balaton (Hungary) by Means of Chlorophyll Fluorescence Studies
140 Makra, L. et al. Keywords : reed, Phragmites ausiralis, die-back; functional state; chlorophyll fluorescence; photosynthesis Abbreviations used: Fo: initial, Fi: intermediate, and Fm maximum fluorescence level, Fv: variable fluorescence, Fv/Fm: efficiency of open PSII units in darkness, Rfd: ratio of fluorescence decrease for chlorophyll. Introduction In recent decades, the common reed (Phragmites australis (Cav.) Trin. ex Steud.), the dominant macrophyte species of shallow lakes in Eastern, Middle and Western Europe, has displayed a significant die-back tendency (Den Hartog et al., 1989; Ostendorp, 1989; Erdei et al. 2001). The tendency to die back is typical of tetraploid (2n=48) reeds that are most commonly indigenous in European lakes, including Lake Balaton (Kovács et al., 1994; Clevering and Lissner, 1999). However, the primary causes have not yet been unambiguously clarified. Our current knowledge suggests that die-back is a complex situation that can result from several causes, e.g. stabilised water tables, mechanical damage, prolonged insect and fungal infestations, eutrophication and phytotoxin damage to the reed. Human activities resulting in eutrophication are probably acting continuously to promote the dying-back of reed-beds (Armstrong et al., 1996.; Ostendorp, 1989; Den Hartog et al., 1989), though Van der Putten (1977) claims that the eutrophication effect is only an indirect one. With regard to the stabilised water table, the reed-beds in Lake Balaton are probably expanding only vegetatively, via rhizome or ramet fragments. Their die-back may therefore be associated with limited genetic variability within the reed populations. The exact functional state of the reed-beds at Lake Balaton, which has never been measured to date. A wide range of studies have established that fluorescence is a sensitive indicator of damage to photosynthesis, to the physiological effects which feedback photosynthesis, and hence to the physiological state of the plants in general (Renger and Schreiber, 1986; Strasser et al., 1987; Lichtenthaler, 1988); it can therefore reveal the effects of stress and environmental factors on plants. It is important that such changes can be expressed by exact numbers, i.e. by the fluorescence induction parameters. The objective of the present research was to investigate the current functional state of the reeds along the shores of Lake Balaton by the application of chlorophyll fluorescence measurement techniques. To reveal how measurements of chlorophyll fluorescence induction can be applied to problems relating to the dying-back of reed-beds, direct measurements of
