Effect of light, gibberellic acid and nitrogen source on germination of eight taxa from dissapearing European temperate forest, Potentillo albae-Quercetum.

Little is known about how light affects seed germination and revegetation of species of thermophilous oak forest. To reveal this relationship effects of white, red, far-red irradiations and dark incubation on germination of eight Potentillo albae-Quercetum taxa were examined. Attempts were also made to evaluate the influence of gibberellic acid and different nitrogen sources on the germination characteristics. Interaction between light and nitrogen was also studied. Freshly matured seeds of all taxa germinated very poorly, indicating presence of primary dormancy. Germination rates increased after wet-stratification treatment and were low in darkness. The highest concentration of the nitrogenous solutions that resulted in high germination level was 10 mM, whereas higher concentrations had a negative effect. Nitrate had the strongest influence which can be proved by a 'gap detection' mechanism for gaps in the vegetation. Far-red and red irradiation showed antagonistic effect on seed germination. There was a decrease in germination when far-red was followed by red and an improvement when red was followed by far-red treatment. Under red light, gibberellic acid enhanced germination of positively photoblastic taxa. It was concluded that light factor, associated with vegetation gaps, was the most important signal stimulating germination of the studied taxa.