JXB Advance Access originally published online on July 4, 2005
Journal of Experimental Botany 2005 56(418):2047-2058; doi:10.1093/jxb/eri203
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
RESEARCH PAPER |
Plasticity and acclimation to light reflected in temporal and spatial changes of small-scale macroalgal distribution in a stream
Institut für Allgemeine Botanik, Universität Jena, Am Planetarium 1, D-07743 Jena, Germany
* Present address and to whom correspondence should be sent: Environmental Stress Biology Group, University of Western Ontario, London, Ontario Canada N6A 5B7. Fax: +1 519 661 3935. E-mail: iensming{at}uwo.ca
The small-scale distribution pattern of macroalgae in the river Ilm, in Germany was monitored. These patterns were then related to abiotic factors and tested to discover whether the distribution of the common macroalgae, Cladophora glomerata (L.) Kütz. and Vaucheria sp., was linked to differences in their photosynthetic plasticity. Cladophora glomerata revealed higher maximum photosynthetic electron transport rates after acclimation to high light (HL) compared with low light (LL) acclimated samples. By contrast, Vaucheria sp. did not acclimate to different growth light conditions. The photosynthetic performance of both algae also varied according to diurnal conditions. High light caused a reversible decrease of the dark-adapted quantum yield (Fv/Fm) in C. glomerata and a concomitant reversible decrease of the light-adapted quantum yield 
In Vaucheria sp., Fv/Fm remained mostly unchanged over the day, whereas 
decreased during the morning at low light. Photosynthetic pigments confirmed acclimational differences between the species. HL C. glomerata showed increased chlorophyll a:chlorophyll b ratios, and higher amounts of xanthophyll-cycle pigments compared with LL samples, whereas Vaucheria sp. did not reveal differences between the light treatments. While preferences for substrate size, water velocity, and depth are similar for C. glomerata and Vaucheria sp., the physiological responses to light conditions are different. It is concluded that light conditions significantly affect the small-scale spatial distribution of macroalgae and that fitness is enhanced in species with a higher plasticity in photosynthetic acclimation in unstable environments.
Key words: Electron transport, environmental conditions, freshwater algae, photoinhibition, spatial distribution, xanthophyll cycle