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The lignin contents and anatomical structure of roots of wild cherry (Prunus avium L.) and pedunculate oak (Quercus robur L.) plantlets were compared to explain differences in response during transfer from in vitro to ex vitro conditions. Lignification of cell walls increased significantly in both oak and cherry roots during the period of acclimation and finally lignin content of root tissues of in vitro propagated plantlets reached the levels not significantly different from seedlings grown in soil. Later on when secondary tissues appeared, lignified secondary xylem constituted most of the tissues of both species. The most conspicuous interspecific difference in root structure was the presence of phithickenings in cortical layers just outer to endodermis in cherry roots cultivated ex vitro. Formation of phi-thickenings was avoided in vitro and their presence thus seems to be under environmental control. Suberised well established exodermis was present in roots of oak but not detected in those of cherry. Very early development of exodermis in oak roots, preceding suberisation of endodermis, was recorded in vitro but not in well aerated soil. While multilayered and well-developed cork occurred in oak, only thin walled and less suberised secondary dermal tissues were found in cherry.

The effect of inhibition of phenylpropanoid biosynthesis on the growth of Medicago sativa L. suspension culture was studied. 2‐Aminoindan‐2‐phosphonic acid (AIP), a potent inhibitor of phenylalanine ammonia‐lyase (PAL; EC 4.3.1.5), caused a marked reduction in the amount of hydroxycinnamic acid derivatives in a few hours after cell inoculation into AIP medium. The treatment of alfalfa suspension culture with this inhibitor increased the extractable PAL activity and elevated ethylene production during the growth cycle. The addition of AIP (10 μM) stimulated cell division activity during the growth cycle, although the onset of cell division was slightly delayed. The maxima of cytokinin content as well as of the mitotic index were postponed in AIP‐treated cells, however, the unchanged content of cytokinins did not correlate with increased mitotic activity of treated cells. The decreased level of hydroxycinnamic acid derivatives, which represent the phenolic conjugation partners of free polyamines (PAs), influenced the rate of PA conjugation. Consequently, the balance between free and conjugated PAs was shifted in favor of the free PA form. A potential role of the reduction of the pool of phenolic acids in the enhancement of cell division of alfalfa cell suspension culture is discussed.

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ABSTRACT:We examined defence responses in embryogenic cell suspension cultures of Norway spruce (Picea abies [L.] Karst) elicited by intracellular protein and cell wall fractions (PF and WF, respectively) prepared from mycelia of the fungus Sirococcus strobilinus Preuss focusing on changes in (soluble and cell wall-bound) phenolic and stilbene concentrations. Treatment with both preparations induced an increase in the total contents of phenolic acids in Norway spruce cells and variations in the levels of stilbene glycosides. More rapid and intense induction of defence response was observed in cells after WF application. The contents of soluble phenolic acids (especially benzoic acid derivatives) and cell wall-bound phenolic acids (especially ferulic acid) started to increase (relative to controls) within 4 h after the addition of the WF preparation and remained high in elicited cells for 8-12 h. A moderate increase in phenolic acids in cells exposed to the PF preparation was observed within 8 h after application. However, after 24 h of WF treatment a decline of total phenolics was observed, while in PF elicited Norway spruce cells the phenolic content continued to increase. Significantly decreased concentrations of stilbene glycosides, isorhapontin, astringin and piceid, were determined in PF and WF treated Norway spruce cell cultures. The total content of stilbene glycosides decreased within 8 h after WF application to 68% of the amount determined in the control and within 12 h to 73% of the control in PF-treated cells. These results demonstrate that both PF and WF prepared from the Sirococcus strobilinus mycelium elicit changes in the metabolism of phenylpropanoids, which are involved in the defence responses of plants to pathogens.

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