In vitro germination and seedling development of Posidonia oceanica

The effects of culture media and fruit storage on germination, development and survival of seedlings of Posidonia oceanica (L.) Delile (Posidoniaceae) were investigated under axenic conditions. Seeds germinated within 15–18 days both on solid media and in liquid over solid media as well as on filter-paper bridges over liquid media. The results showed a significant effect of the culture medium on germination and survival of seedlings among the solid media and the liquid over solid media tested. The highest mean germination (96.2%) was found in the solid artificial seawater medium (ASW). Only solid or liquid/solid ASW medium, however, allowed continuous growth of seedlings. Addition of nutrients and inclusion of the plant growth regulator 2,4-dichlorophenoxyacetic acid (2,4-D) inhibited development of seedlings. After 10 months, the highest mean survival (75%) was reached on solidified ASW following addition of liquid medium. No significant effect of the culture medium on seed germination and seedling survival was seen using the paper-filter bridge technique. With the latter method, germination and survival rates ranged from 54 to 85% and from 31 to 58%, respectively. All seedlings showed continuous growth. Addition of nutrients, however, reduced the production of adventitious roots. The results also showed significant effect of fruit storage treatment on the fruit surface-sterilization success, but not on seed germination or seedling survival. In vitro raised seedlings of P. oceanica appear to be useful for conservation and propagation of this species.