Am. J. Bot.
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(American Journal of Botany. 2007;94:1972-1983.)
© 2007 Botanical Society of America, Inc.

Phycology

High salinity alters chloroplast morpho-physiology in a freshwater Kirchneriella species (Selenastraceae) from Ethiopian Lake Awasa1

Lorenzo Ferroni, Costanza Baldisserotto, Laura Pantaleoni, Paolo Billi, Maria P. Fasulo4 and Simonetta Pancaldi

Laboratory of Plant Cytophysiology, Department of Biology and Evolution, University of Ferrara, Corso Ercole I d'Este, 32 – 44100 Ferrara, Italy; Department of Earth Sciences, University of Ferrara, Via Saragat, 1 – 44100 Ferrara, Italy

ABSTRACT

Plants differ in their ability to tolerate salt stress. In aquatic ecosystems, it is important to know the responses of microalgae to increased salinity levels, especially considering that global warming will increase salinity levels in some regions of the Earth, e.g., Ethiopia. A green microalga, Kirchneriella sp. (Selenastraceae, Chlorophyta), isolated from freshwater Lake Awasa in the Rift Valley, Ethiopia, was cultured in media amended with 0, 0.4, 1.9, 5.9, and 19.4 g NaCl·L–1 adjusted with NaCl to five salinity levels adjusted with NaCl. Growth was monitored for 3 mo, then samples were collected for photosynthetic pigment determinations, microspectrofluorimetric analyses, and micro- and submicroscopic examinations. The best growth was found at 1.9 g NaCl·L–1. In the chloroplast, excess NaCl affected the coupling of light harvesting complex II and photosystem II (LHCII-PSII), but changes in thylakoid architecture and in the PSII assembly state allowed sufficient integrity of the photosynthetic membrane. The mucilaginous capsule around the cell probably provided partial protection against NaCl excess. On the whole, the microalga is able to acclimate to a range of NaCl concentrations, and this plasticity indicates that Kirchneriella sp. may survive future changes in water quality.

Key Words: chloroplast • Ethiopian Rift Valley • Kirchneriella • Lake Awasa • microspectrofluorimetry • photosystem II • salinity • ultrastructure






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