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The germination of Empress tree (Paulownia tomentosa Steud.) seeds is phytochrome-controlled. Liquid smoke could not induce germination in darkness but red light irradiation of liquid smoke imbibed seeds induced a high percentage of germination. Maximum germination was achieved at liquid smoke concentration of 0.1% (v/v) when present during the imbibition phase or during the phase of phytochrome activity. The light requirement of these seeds could be completely substituted by exogenously applied gibberellins. In the presence of liquid smoke, optimal concentrations of GA(3), GA(4), and GA(9) necessary for inducing germination were several times lower than in the controls, while that of GA(7) was equally active when applied at a concentration one order of magnitude lower. The inhibitory effect of the applied growth retardants was strongly reduced and liquid smoke, in the presence of retardants, allowed light-induced germination, if applied simultaneously or after retardants treatment. null

A wide range of sucrose, fructose, and glucose levels in culture media was tested in vitro in order to determine those that provide optimum growth, morphogenesis, and the production of secondary metabolites in Nepeta rtanjensis Diklic and Milojevic shoots. The effect of different concentrations of the carbohydrates in culture media on the internal carbohydrate status of N. rtanjensis shoots was also determined. Our results show that in vitro growth and development of N. rtanjensis, as well as nepetalactone accumulation, are significantly affected by both the type of carbohydrate and its concentration in the culture medium. Glucose proved to be the most efficient carbon and energy source. null

A micropropagation protocol was developed for the conservation of critically endangered Serbian perennial Nepeta rtanjensis (Lamiaceae). Rooted shoots were obtained from one-node stem segments and shoot tips on a half-strength Murashige and Skoog (MS) medium without growth regulators. The best pH of the medium for axillary buds induction and for rooting of shoots was found to be at 7 and/or 7.2 respectively. The addition of cytokinins to the culture medium did not significantly stimulated auxillary bud production as compared to the control. On the contrary, on media supplemented with high cytokinin concentrations, only dwarf shoots with rudimentary roots were obtained. All tested concentrations of 6-benzylaminopyrine (BAP) and kinetine (Kn) in combination with 0.1 mg 1(-1) indole-3-acetic acid (IAA) negatively affected the elongation and rooting of shoots. Plants micropropagated on hormone free medium and rooted in vitro were successfully acclimatized in greenhouse and in open field conditions. The result of successful acclimatization was the production of more than 7000 plantlets with normal sexually reproduction. They flowered, fruited and produced seeds which exhibited 47% germination. The survival rate of plants that were transferred to the open field for the acclimatization and exposed to the winter chill was 99%. The reintroduction of N. rtanjensis occurred in May 2004. One thousand plantlets were planted within the historic range of this plant species. The survival rate was also 99%. null

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Nitrates have long been known to promote seed germination in many species, and various proposals have been made regarding the role of nitrates in this process. One hypothesis suggests a possible ecological role for nitrate, providing the seeds with a report of soil nitrogen status and the proximity of already established plants. However, nitrogen oxides (NO, NO2), which are present in the soil, also may be information carriers that indicate not only soil nitrate content, but also microbial activity and, therefore, soil quality. Because of annual variation of soil trace gas fluxes, seeds could be provided with information on seasonal and climate changes in their surroundings. Thus, nitrogen oxides would be the outer information carriers providing the seeds with integral data about many important factors required for successful germination and seedling establishment. null

Nitrogenous compounds, such as potassium nitrate, potentiate germination of different species of light-requiring seeds. Using light-induced Arabidopsis thaliana seed germination as a model system, our data suggested that only phytochrome A (phyA)-specific induced germination was affected after the exogenous application of nitrates, different nitric oxide (NO)-donors (such as organic nitrates) or sodium nitroprusside. The stimulative effect was very pronounced. Treated seed samples reached maximal germination after very short periods of red-light irradiation. To a far lesser extent, these substances affected phytochrome B (phyB)-specific induced germination. In phyB-specific induced germination, potassium nitrate was most effective, but germination percentages never exceeded 50%. The least effective was sodium nitroprusside, which practically did not affect phyB-specific induced germination. These results were confirmed using corresponding phytochrome mutants. null

Using different nitric oxide releasing compounds and appropriate controls we have obtained data strongly suggesting the involvement of nitric oxide in the phytochrome controlled germination of Paulownia tomentosa seeds. Direct detection of nitric oxide, under various experimental conditions, was performed by a spin-trapping technique combined with electron paramagnetic resonance (EPR) spectroscopy. The addition of methylene blue prevented light-induced and NO donors-potentiated germination of P. tomentosa seeds. This inhibition could be completely overcome by addition of gibberellin. The promotive effect of nitrite was pH dependent, maximally pronounced at the pH range where nitrite undergoes dismutation and liberates nitric oxide. Under these conditions, nitrite exerted its efficacy at the same concentrations at which nitric oxide releasing compounds such as sodium nitroprusside (SNP), S-nitroso acetylpenicillamine (SNAP), and 3-morpholinosydnonimine (SIN-1), were the most effective. Likewise, the potentiation of P. tomentosa seed germination could be achieved by chemical reduction of nitrite with Na2S2O4 during which liberation of nitric oxide could be detected. null