Exposure to red light, temperature and exogenous gibberellins influenced germination of some winter weeds
Red light, temperature and gibberellins are well known for their capacity to induce higher germination in dormant seeds of several plant species. In the current study, we investigated the effect of various temperature (10, 13, 16, 19, 22 and 25°C) and gibberellic acid (GA3) and GA4+7 concentrations (0.1, 1, 10, and 100 uM) on germination of Poa annua, Alopecurus aequalis and Stellaria aquatica seeds incubated under continuous dark or treated with red light pulse of 80 mol m-2 s-1 red light (660 nm) for 10 min after 12 h of dark period. We found that incubation temperature and gibberellins (GAs) significantly enhanced seed germination in red light treated seeds, as maximum germination was observed for A. aequalis (67.3% at 13°C), P. annua (61.3% at 13°C), and S. aquatica (42% at 19°C) in such treatments. Exogenous GA4+7 significantly promoted germination of P. annua and A. aequalis seeds, while GA3 induced higher germination in S. aquatica seeds. It was observed that GAs were more effective in the presence of red light as least germination stimulation was recorded for GAs under dark condition and no germination was found in weed seeds at control and 0.1 mM GA3 and GA4+7 treatments. It can be concluded that lower temperature (13°C) and GA4+7 in conjunctions with red light pulse, induced maximum germination in dormant weed seeds.
Key words: Germination, temperature, nitrogen-containing compounds, red light, gibberellins.