Effect of nitric oxide - releasing compounds on phytochrome - controlled germination of Empress tree seeds

Using different nitric oxide releasing compounds and appropriate controls w e have obtained data strongly suggesting the involvement of nitric oxide in the phytochrome controlled germination of Paulownia tomentosa seeds. Direc t detection of nitric oxide, under various experimental conditions, was per formed by a spin-trapping technique combined with electron paramagnetic res onance (EPR) spectroscopy. The addition of methylene blue prevented light-i nduced and NO donors-potentiated germination of P. tomentosa seeds. This in hibition could be completely overcome by addition of gibberellin. The promo tive effect of nitrite was pH dependent, maximally pronounced at the pH ran ge where nitrite undergoes dismutation and liberates nitric oxide. Under th ese 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 ge rmination could be achieved by chemical reduction of nitrite with Na2S2O4 d uring which liberation of nitric oxide could be detected.