virginiana(a nonphotosynthetic parasitic plant) showing that all photosynthetic genes are missing and
that the plant does not contain any of the genes that have been described in the context of chlororespira-
tion up to now [116].
IV. ENVIRONMENTAL ASPECTS
Plant physiological investigations play an essential role in the modern detection and quantification of the
detrimental effects of air pollutants, plant protective chemicals, and other (possibly problematic) sub-
stances. Fluorescence emission parameters have been shown to reflect directly the “fitness” of plants, and
in many cases injuries or damage by pollutants or toxic substances, early phases of diseases, etc. have
been inferred from effects on fluorescence long before macroscopic parameters (e.g., lesions) on leaf sur-
faces could be observed. The techniques are based principally on the classical work by Duysens and
Sweers [117], who observed and described the specificity of room temperature fluorescence for photo-
system II and many details of the process. Since then, fluorescence emission measurements have been
used to investigate the effects of chemicals of any type on plants. In other cases, the technique has been
(“inversely”) adapted to examine the load, e.g., of local water (in lakes, brooks, or rivers) by simply
adding the respective probe to plants or algae and recording the resulting fluorescence behavior of the test
organism. One of the main advantages is that the industry now offers simple, compact, and handy instru-
ments and the result is obtained almost immediately.
In our laboratory, we have shown that simple spray application of plant protective chemicals such as
triforine fungicides and pyrethroid insecticides (in any case, nonherbicides) to intact leaves of tobacco
(Nicotiana tabacum) results in an increase of the maximal fluorescence emission (Fmax) and a much less
pronounced Kautsky effect [118,119]. This was a completely unexpected result because fungicides and
insecticides were not supposed to have any negative effect on plants. In the case of the pyrethroid insec-
ticides, the site of inhibition of fenvalerate could even be localized (by means of oxygen gas exchange
analyses) and shown to be identical to that of the standard herbicide(!) diuron (DCMU), namely QB, on
the acceptor side of photosystem II. The ferricyanide Hill reaction was clearly inhibited, whereas the sil-
icomolybdate Hill reaction and the DPiP Mehler reaction were not affected [118,119]. Mass spectromet-
ric techniques have been applied not only for gas analyses in plant physiology but also for the detection
and enrichment of compounds, e.g., in whole plants. Thus, polycyclic aromatic carbohydrates have been
detected and analyzed at m/e128–202 in probes from plant tree bark. These measurements appeared
suited for estimation of pollution (e.g., from traffic) in both urban and rural environments [120].
Recent experiments have dealt with the effects of inorganic compounds such as metal ions and salts
on plant physiological processes. Such parameters can be evaluated in terms of both optimal nutrient sup-
ply and pollution of the environment, depending on the concentration of the respective molecule. Algae
and cyanobacteria are very sensitive to modifications of their aqueous environment and are in many cases
well suited for such studies with respect to physiological gas exchange reactions. The oxygen evolution
flash pattern (see Sec. II) of Oscillatoria chalybeawas substantially modified by addition of various in-
organic salts (Figure 14). Although we carried out the experiments with rather intact protoplasts, the pho-
tosynthetic apparatus was apparently salt limited in the sense that higher chloride concentrations were
needed for optimal water oxidation. In this context, manganese (although an indispensable cofactor of the
OEC) played only a minor role as manganese sulfate yielded a smaller stimulation of the oxygen ampli-
tudes. Manganese chloride gave higher yields equivalent to those observed with sodium chloride (result
not shown). Calcium also stimulated the oxygen evolution rates to a substantial extent. These experiments
are under investigation at present and will be discussed in terms of mechanistic implications for the OEC
(S Spiegel, KP Bader, submitted). In these cases, however, the required concentrations were rather high
and ranged up to 400 mM in the in vitro assays.
Interesting results have come from the laboratory of Yoshihiro Shiraiwa, who has investigated the
effects of the trace element selenium on physiological and biochemical parameters in marine coccol-
ithophorids. Addition of selenium to the culture medium of Emiliana huxleyi,Gephyrocapsa oceanica,
andHelladosphaerasp. had significant effects on growth, oxygen gas exchange reactions, and chloro-
phyll content [121]. Figure 15 shows the complex gas exchange analysis in the presence or in the absence
of 10 nM selenite, respectively, for two consecutively (one out of the other) inoculated cultures. Interest-
ingly, the Se-deficient (“first”) culture did not grow at all with respect to an increase in cell number fol-
318 BADER AND ABDEL-BASSET