I. Recording pH changes in different cellular compartments by fluorescent probes. Planta 182:244–252CrossRef”
“Introduction Differences in ITF2357 concentration pigmentation are used to discriminate taxonomic phytoplankton groups in applications ranging from microscopy to remote sensing of water colour. The highest level

of pigment discrimination between phytoplankton groups is found between prokaryotic cyanobacteria and the vast majority of algal taxa. Chlorophylls and carotenoids are dominant in algae, while phycobilipigments (phycoerythrin, phycoerythrocyanin, phycocyanin and allophycocyanin) are the main light harvesting pigments in cyanobacteria (prochlorophytes excepted) and red GDC-0449 molecular weight algae. Phycobilipigments extend the absorption of light to the green-orange part of VX-689 datasheet the visible spectrum that is left unused by the algal groups. This spectral domain overlaps with the deepest penetration of solar irradiance in inland and coastal waters where turbidity and/or the concentration of coloured dissolved organic matter is high, yielding an advantage in light-harvesting

at depth to phycobilin-containing species (Pick 1991; Stomp et al. 2007). Owing to the differences in pigmentation between the major phytoplankton groups, absorption and fluorescence techniques can be used to interpret biomass at the community and sub-community level (Yentsch and Yentsch 1979; Kolbowski and Schreiber 1995; Beutler et al. 2002; Millie et al. 2002;

Beutler et al. 2003; Seppälä and Olli 2008). In vivo chlorophyll a (Chla) nearly fluorescence is a widely used proxy of phytoplankton biomass, a non-intrusive measurement that can be carried out with high spatial resolution (Lorenzen 1966; Kiefer 1973) under the assumption that the Chla fluorescence yield is constant. When excited with blue light, Chla fluorescence per unit concentration in cyanobacteria tends, however, to be up to an order of magnitude lower than in algae, which results in erroneous biomass estimates unless corrected for (Vincent 1983; Seppälä et al. 2007). The distribution of Chla between photosystems I and II (PSI, PSII) is fundamentally different in these phytoplankton groups (Johnsen and Sakshaug 1996, 2007), and requires consideration in all aspects of phytoplankton community fluorescence measurements. Variable fluorescence methods relate the rise of fluorescence that occurs with ‘closure’ of PSII centres under saturating illumination to energy flow in PSII (Kautsky and Hirsch 1931; Genty et al. 1989). Closed reaction centres cannot use the energy absorbed in the photosystem antennae for photochemistry and emit at least part of the excess energy as fluorescence (e.g. Gilmore and Govindjee 1999). Saturating light conditions can be induced by generating intense light pulses, such as used in pulse-amplitude modulation (PAM), pump-and-probe and fast-repetition rate fluorescence (FRRF) techniques.