Culture filtrates (conditioned medium, CM) containing exudates obtained from cells of Scenedesmus subspicatus grown in batch culture were tested for their autoinduction activity. Undiluted CM completely inhibited the proliferation of cells due to depletion of nitrogen in this medium. When undiluted CM was supplemented with fresh bold basal medium (BBM) medium, enhancement of population growth in a dilution-dependent manner was observed. The most effective was 2-fold diluted CM (CM/2), whereas the growth activity of CM/20 decreased considerably. The proliferation of cells at a very low initial density (10 cells mL −1 ) was induced by the addition of CM/2. Biovolume, dry matter production and oxygen evolution by cells grown in 2-, 5-and 10-fold diluted CM increased markedly in both a concentration-and time-dependent manner. Conditioned medium factor (CMF) was mainly a product of rapidly dividing cells. Preliminary characterisation revealed that CMF is heat-stable, resistant to very low pH, highly hydrophilic (poorly soluble in ethanol or diethyl ether) and diffuses through a 1 kDa dialysis membrane. CM can be stored for long periods due to the time-stable activity of CMF. Depending on the enzyme applied, proteolytic digestion completely (papain, bromelain) or partially (subtilisin) abolished the activity of CM. This effect of CM was enhanced by digestion with trypsin. We suggest that CMF may be a low-molecular-weight peptide(s) or glycopeptide(s).

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The study aimed at evaluating the response of common plum (Prunus domestica L.) microshoots during in vitro rooting in the presence of two phytoactive medium supplements, i.e. a dialyzate of pineapple pulp and a conditioned medium containing green algae Desmodesmus subspicatus exudates. Rooting efficiency was evaluated after 4 weeks of culture. During the root induction phase the content of phenolic compounds in shoot bases was determined and anatomical studies were conducted. Medium supplements were analyzed for the content of carbohydrates and phenolic acids. Both supplements were efficient in rooting induction of shoots of a difficult-to-root cultivar 'Węgierka Zwykła'. Medium supplementation allowed a significant reduction in the exogenous auxin content required for rooting. The highest rooting efficiencies on supplemented media were 28.9 and 27.8 %, in comparison with 33.3 % obtained in the control medium with doubled concentration of exogenous auxins. In the easy-to-root plum cultivar 'Węgierka Dąbrowicka' the rooting rate was slightly reduced in the presence of pineapple dialyzate, while in the presence of algal conditioned medium the rooting rate decreased substantially compared with the nonsupplemented medium. Approximately 30 % of 'Węgierka Dąbrowicka' shoots rooted on supplemented auxin-free media. The content of phenolic compounds accumulated in shoot bases during the root induction stage reflected the differences in rooting ability between both plum cultivars, indicating potential stressful conditions of the culture generated by the presence of phytoactive natural supplements. Anatomical study allowed to recognize the mode of dedifferentiation leading to adventitious rhizogenesis in the common plum. The results are discussed in relation to the composition of medium supplements and their potential root-promoting activity.

Although the appearance of coloured chlorophyll degradation products of higher plants is well known, knowledge about such compounds produced and released particularly by planktonic algae is still limited. Colourless conditioned media (CM) obtained from autotrophic cultures of unicellular green alga Desmosdemus subspicatus turn red after acidification. The accumulation of red pigments in the medium and the growth rate of algae were inversely correlated. The red, crude solution isolated from CM by dialysis and ion exchange chromatography, and next purified by means of high-performance liquid chromatography, appeared to be a mixture of three compounds with characteristic UV/VIS absorption maxima near 330 and 505 nm. Electrospray ionization (ESI) mass spectrometry analysis revealed that the molecular mass of the most polar and most abundant compound was 637 Da and molecular masses of two other ones were 641 and 607 Da. Addition of 15 N isotope to the culture medium and subsequent mass spectrometry measurements revealed the occurrence of four nitrogen atoms per each molecule. The data suggest that red pigments isolated from algal-conditioned media are chlorophyll degradation compounds, the production of which depends on light intensity, and are released mainly during the stationary phase of growth.

The effect of culture filtrate (conditioned medium, CM) containing cell exudates obtained from green alga, Scenedesmus subspicatus, on cell suspension of dicotyledonous plant Silene vulgaris was examined. The addition of diluted CM to the modified MS medium, supplemented with dicamba and BAP, stimulates cell biomass production. The biomass was composed of association of single non-dividing cells, cells during mitosis stage and cellular aggregates. Silene cells began mitotic divisions earlier in the presence of CM in medium when compared to control treatments. Results of performed bioassay showed that some factor or factors released by green alga to the culture medium could be responsible for sustained proliferation of phylogenetically distant species cells. Although it is still unclear which culture constituent influenced most the mitotic response of Silene suspension, results point at versatile stimulatory character of green alga exudates in higher plant cell culture.