Acta Univ Latv (2008) 745: 155–164

Photosynthetic performance and mycorrhizal symbiosis of a coastal marsh plant, Glaux maritima, in conditions of fluctuating soil salinity

Abstract

The aim of the present study was to explore the effect of seasonal fluctuations of soil salinity on chlorophyll a fluorescence and mycorrhizal symbiosis of Glaux maritima L. plants in natural conditions. Two neighboring sites with different flooding regime and putatively different soil characteristics were chosen for the investigation. The two sites significantly differed in salinity and both macronutrient and micronutrient concentrations. The relatively more sea-affected site A had higher salinity and higher concentrations of most nutrients. Potential quantum yield of photosystem II (FV/FM) decreased to an extremely low level in plants at site A in July indicating photoinhibition of photosynthesis. In contrast, a relatively low increase of soil salinity did not affect FV/FM at site B. Decreased photosynthetic performance at site A in July was reflected also by a drastic decrease both in photosystem II activity as well as in the ratio of active reaction centres. G. maritima plants were characterized by a low level of intensity of mycorrhizal symbiosis throughout the vegetation season while the frequency of infection in general was higher. Both parameters showed significant changes during the season. Anatomy of root colonization showed distinct patterns at the two study sites with mostly intracellular hyphae forming hyphal coils in roots of G. maritima at site A in contrast to site B where predominantly external hyphae were found. Mycorrhizal symbiosis could be regarded as a significant part of the adaptive mechanisms of G. maritima.