Abnormal embryo development in the seagrass Posidonia oceanica

In this study the occurrence of twin-like embryos and abnormal embryos in Posidonia oceanica, a rare phenomenon in seagrasses, was documented. The ability of additional embryos to develop seedlings was also demonstrated for the first time in seagrasses. Approximately 1750 fruits collected at three localities of the north-western Mediterranean on 2 years (1994 and 2004) were screened for abnormal embryo morphology. The frequency of embryo anomalies varied from 1.9 to 7.1% among localities, and no differences between years were detected within the same locality. Twin-like embryos were usually in contact and germinated to produce complete twin seedlings that could be separated. Abnormal embryos showed additional plumules but had a common hypocotyl and a single primary root; these embryos germinated and grew like “Siamese” seedlings.