In black pine (Pinus nigra) chlorophyll was first detected two days after planting of the soaked seeds. There "was a slight change in the chlorophyll content betweien two and five days, then a faster chlorophyll synthesis: started. The maximum chlorophyll content was found after 15 days of germination. Thereafter the content showed a gradual decrease. The chlorophyll a/b ratio decreased from 10 at two days to 3 after five days. Protochlorophyilide did not accumulate after 6 days of germination.

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Soybean plants cv. Corsoy were grown in greenhouse conditions on sterilized quartz sand. They were inoculated with Bradyrhizobium japonicum, strain 542. The plants were treated with different concentrations of quercetin (ranging from 10 nM to 1/~M at regular intervals during the experiment. The experiment was terminated at flower development. The following parameters, important for symbiosis efficiency were determined: shoot, root and nodule weights, nodule number, total leghemoglobin in the nodules,total nitrogen and soluble protein concentrations in shoots and roots, as well as chlorophyll concentration in the leaves.The results obtained partly confirmed the earlier findings that quercetin inhibits nodulation since increasing quercetin concentration decreased the number of nodules. However, at very low concentrations, quercetin stimulated the number of nodules. Quercetin also exerted a stimulating influence on other characteristics of the plant and nodules which did not correlate with nodule number and quantity of N fixed. These are: nodule weight, leghemoglobin concentration, total soluble protein content in shoots and roots as well as shoot and root weight.

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The existence of an oxygen dependent pH-gradient across the thylakoid membrane in the dark led to the hypothesis of a chlororespiration in Pleurochloris meirmgensis. Measuring flash-induced absorbanee changes at different wavelength and mathematical fitting of the transient spectra absorbance changes around 515 nm were attributed to an electrochromic shit~ in these chl-b and hitein-less organisms. Adding 2 mM KCN increased the slow phase of the electrochromic absorbance change. The enhanced activity of the cytochrome (cyt) f due to KCN was further demonstrated by the absorbance changes at 553 nm, where a stronger oxidation of the cyt as well as an accelerated reduction became visible favouring the idea of an oxidase competing with the cytf for electrons. The KCN-coneentration needed to induce this effect was 0.25 mM for half saturation, wheareas mitochondrial respiration was completely blocked adding 0.1 raM. Therefore we conclude that there is a KCN-sensitive oxidase located in the thylakoids ofP. meiringensis.

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