THE GERMINATION CHARACTERISTICS OF A POPULATION OF ZANNICHELLIA-PALUSTRIS SUBSP PEDICELLATA

In this study the germination characteristics of Zannichellia palustri s L. subsp, pedicellata (Wahlemb. et Rosen) Hegi seeds collected from a population along the margin of the Orbetello Lagoon (Tuscany, Italy) was examined. The effect of variations in duration of seed after-ripe ning and environmental parameters such as light, temperature and cultu re medium salinity on germination was assessed, In addition, germinati on ability of seeds subjected to stratification (+4 degrees C for 30 d ays) and differing in morphology was evaluated. A constant temperature of 20 degrees C was optimal for germination, while alternating temper atures of 10/20 and 20/30 degrees C were highly unfavourable and frequ ently produced no germination. Darkness inhibited germination but this was overcome by a period of stratification. At 20 degrees C seed germ ination showed a sinusoidal trend linked to seasonal changes. A dimorp hism in Z. palustris achenes was observed, Such achenes were also foun d to differ in germination response, The pronounced control over germi nation exerted by this species could represent one of its main surviva l strategies, allowing reproduction in unstable environments character ized by variations in salinity such as were observed in the area under investigation.