VEGETATIVE REPRODUCTION IN POSIDONIA-OCEANICA - SURVIVAL AND DEVELOPMENT IN DIFFERENT MORPHOLOGICAL TYPES OF TRANSPLANTED CUTTINGS

The number of leaf bundles and the growth mode of the principal axis w ere used to define morphological type in cuttings of the Mediterranean seagrass Posidonia oceanica (L.) Delile. Survival and development wer e compared in cuttings of three morphological types: orthotropic, with respectively one and two leaf bundles and plagiotropic with three bun dles (one terminal and two lateral). A total of 216 cuttings were tran splanted at their depth of origin, 14 m. Both orthotropic and plagiotr opic cuttings were fixed in a horizontal position. After 11 months, th e initial three-bundle plagiotropic cuttings showed 100% survival; 49% had formed new branches and 97% had formed new roots. Corresponding p ercentages for two-bundle initially orthotropic cuttings were 94%, 8% and 62%, and for one-bundle orthotropic cuttings only 31%, 9% and 14%. Initially orthotropic material was transformed into the plagiotropic growth mode. This was associated with the horizontal transplanting pos ition, as shown by change in the direction of growth of the leaf bundl es. The leaves grew curved and shorter, increasing in number in each b undle and greater rates of both formation of new roots and branches we re observed. For transplantings planned in connection with biotope res toration, cuttings should be selected which bear at least two leaf bun dles and which, if possible, are plagiotropic.