Germination of turions in Potamogeton berchtoldii [Aquatic plants]

Investigation of the effects of environmental factors-photoperiod, temperature, and light quality-and growth regulators-gibberellic acid (GA8), and indoleacetic acid (IAA)-on the release from dormancy in turions of Potamogeton berchtoldii showed that, after 33 days at 0 C, turions germinated very rapidly. Treatment at 2 C for 35 days was sufficient for germination, but longer cold periods, up to 75 days, induced greater and faster germination and more rapid growth in shoot and root lengths. Chilling at 2 C for 32 days released turions from dormancy in all photoperiods. Non-cold-treated turions failed to germinate under all photoperiods. Red and far-red irradiation after cold treatment promoted germination; blue light markedly inhibited germination. With GA8or IAA, non-cold-treated turions germinated; IAA was more effective than GA8in promoting shoot elongation. Concentrations of 10-4M GA3were toxic to growth and development after germination; however, apparently normal growth was observed at 10-4M IAA.