Seagrass meadows provide an essential ecological service in coastal ecosystems worldwide, although they are sensitive to many human factors, as a serious global regression has been documented. During sampling along the Atlantic Moroccan coast, five coastal lagoons were found characterized by the presence of intertidal monospecific seagrass Zostera noltii meadows (from south to north, Nayla, Oualidia, Sidi Moussa, Moulay Bousselham, and Larache). Two descriptive methods used to characterize Z. noltii populations could be used as management tools for future monitoring implementations: (1) the estimation of surface area covered by Z. noltii meadows using remote sensing techniques and in situ field surveys, and (2) the genetic characterisation of Z. noltii populations using simple sequence repeats (microsatellites) as molecular markers. Results revealed that the Nayla lagoon showed the largest area covered by Z. noltii (269,868 m 2 ) and the highest coverage rate (5.19%), while presenting the lowest genetic/genotypic diversity values (T ¼ 36, Â ¼ 3.58, G ¼ 50; R ¼ 0.544; H e ¼ 0.43). On the other hand, northern populations displayed lower rates of seagrass coverage (~1%) and higher values of genetic/genotypic diversity. Further genetic characterization also revealed that Z. noltii populations seem to be highly isolated in three geographically independent regions: northern Morocco (R1, Larache and Moulay Bousselham), central Morocco (R2, Oualidia and Sidi Moussa), and southern Morocco (R3, Nayla), which should be considered independent management units. Both seagrass coverage rate and the genetic description of seagrass populations along the Atlantic Moroccan coast seem to be useful management tools that could be used to evaluate changes in seagrass meadows over time to further establish appropriate conservation strategies.

Endogenous polyamine (PA) content in the seagrass Cymodocea nodosa was monitored at different embryo and seedling developmental stages. Total PA concentration, including putrescine (Put), spermidine (Spd) and spermine (Spm), and the Put (Spm + Spd) −1 ratio decreased during embryo development, from the immature fruit to the mature seed stage (with a sharp decline in the free PA fraction), and subsequently increased during germination and seedling development from the cotyledon to seedling stage, indicating an important role during zygotic embryogenesis and seed germination. In particular, total levels of Put and Spm significantly decreased from the fruit to the mature seed, to be restored after germination. Spd levels remained constant during all the developmental stages studied. When seedlings were subjected to hypoosmotic stress (i.e. salinity decrease from 36 to 5 psu), fluorescence levels decreased, reaching a minimum photochemical efficiency (F v /F m) at 5 psu (0.582 ± 0.025, mean ± SE), indicating that seedlings were under high stress. Contrary to expectations, this was followed by a slight decrease in total PA content (showing a significance difference between 5 psu and higher salinities in bound-insoluble PA) and the accumulation of the PA cadaverine (Cad) at 5 psu (indicating cell death), which revealed the inability of this species to face the abiotic stress promoted by long-term salinity decrease. These 2 physiological indicators may suggest that C. nodosa is an obligate halophyte because it requires an environment with relatively high and stable salinity for its survival. Moreover, exogenous application of Spd significantly improved F v /F m values at the lowest salinity treatment (5 psu: 0.670 ± 0.012), which suggests a protective role of Spd in maintaining the photosynthetic apparatus of C. nodosa seedlings under long-term hypo-osmotic stress.

In vitro germinated seedlings of ­Cymodocea nodosa were used as a source of young embryonic tissue for cell culture. Histological study of the cotyledon revealed the presence of meristematic tissue that gave rise to the first leaf of the plantlet, which released large numbers of cells after enzymatic digestion and thus indicated great growth potential. An effective enzymatic digestion protocol for C. nodosa meristem tissue was developed; this consisted of a 24-h digestion period at 28°C using a 0.6-m enzymatic solution (plasmolysis medium containing 1% (w:v) cellulase and hemicellulase). It was necessary to add citric acid (0.02 m) as an antioxidant to the enzymatic solution to obtain the highest cell yield and viability (mean±SE: 371.6±30.1×105 cells g-1 fw and 97.8±0.6%, respectively). NaCl and other salt components of the seawater were key factors in the establishment of axenic cell cultures and their further progress; their absence in the medium inhibited contaminant overgrowth. Nevertheless, cells maintained growth for 90 days, even without hormones and deprived of salts, although these salts might be necessary to allow the development of morphogenetic programmes desired for plant production. In this manner, we generated a basic tool for the future of C. nodosa in vitro culture that will allow the establishment and maintenance of hormone-autonomous cell cultures with strong potential in future biotechnology for marine higher plants.

No abstract