The photosynthetic capacity of the common reed (Phragmites australis /Cav./ Trin. ex Steudel) was studied in various reed stands in the littoral zone of Lake Fertõ. Measurements were performed in three healthy and two die-back reed stands in the summer of 1997. In the leaves of declining reeds, the chlorophyll content was lower than in the vigorous sites. In the former sites, there was a significant rise in the total carotenoid pool (320 - 480 mmol mol-1 ch1 (a + b)) as compared to that of the vigorous sites (250- 350 mmol mol-1 ch1 (a + b). The size of the xanthophyll cycle pool and the β-carotene content of leaves significantly increased in the die-back sites. In early summer, the potential photochemical quantum efficiency of Photosystem II (Fv/Fm) did not differ considerably (0.79-0.81) from site to site, yet by August it significantly decreased (0.74-0.77) in the die-back sites as compared to the vigorous sites. The maximum CO2 assimilation rate measured on the 3rd and 4th leaves ranged from 11 to 17 CO2μmol m-2 s-1 and from 9 to 12 CO 2μmol m-2 s-1 in the vigorous sites and the die-back sites, respectively. The stomatal conductance was also lower in the die-back sites (200-350 mmol H2O m-2 s-1) than in the vigorous reed stands (380-510 mmol H2O m-2s -1) which might result in the functional impairment of the gas ventilation system of the declining reeds, and consequently in oxygen deficiency and damage to the rhizome.
ASJC Scopus subject areas
- Aquatic Science