Hydrodynamically Generated Patchiness in Seagrass Meadows

The mosaic of patterns observed in seagrass landscapes is often a result of natural perturbations such as erosion and burial by sand waves (Harlin and Thorne-Miller, 1982 Fonseca et al., 1983 Marba et al., 1994 Marba and Duarte, 1995 Fonseca and Bell, 1998 Bell et al., 1999 Fig. 12) and or disturbances caused by fauna (Orth, 1975 Ogden, 1980 Preen, 1995), storms (Preen etal., 1995 Fonseca and Bell, 1998) and or disease (den Hartog, 1987). Anthropogenic causes (eutrophication, boat and mooring...

Posidonia Oceanica Medicinal

Ackerman JD (1986) Mechanistic implications for pollination in the marine angiosperm Zostera marina. Aquat Bot 24 343353 Aladro-Lubel MA and Martinez-Murillo ME (1999) Epibi-otic protozoa (Ciliophora) on a community of Thalassia testudinum Banks ex Konig in a coral reef in Veracruz, Mexico. Aquat Bot 65 239-254 Alcoverro T, Duarte CM and Romero J (1997) The influence of herbivores on Posidonia oceanica epiphytes. Aquat Bot 56 93-104 AlongiG, CormaciM and Pizzuto F (1993) La microflora epifita...

Population Structure and Reproductive Strategies

As many of the other chapters in this book will describe, vegetative growth through rhizome extension is a dominant feature of seagrasses. This growth habit allows great flexibility for a single genetic individual to survive in both space and time through clonality resulting from vegetative fragmentation. Most seagrass populations exhibit a mixture of clonal growth along with sexual reproduction and understanding the structure of these populations has proved challenging using standard...

Nitrogen and Phosphorus

In both the Mediterranean and southern Australia, environments are characterized by microtidal regimes and relatively low-nutrient environments. Thus, paradoxically Posidonia species colonize one of the most nutrient-poor environments in the world (e.g. Copin-Montegut, 1996 Walker, 2000). P. oceanica can even colonize ultra-oligotrophic habitats in the Eastern Mediterranean (if this status is defined by the nutrient concentrations and not by the biomass). The nitrogen content in Posido-nia...

Zosteraceae

Pl. (1829) 65, 66 nom. cons. Typus Zoster a L. Monoecious or dioecious marine plants. Rhizome creeping, herbaceous, monopodial or sympodial when monopodial with two vascular bundles in the cortical layer and at each node two or more unbranched roots and a leaf or a prophyllum, with in its axil a short lateral branch bearing a bunch of distichously arranged leaves roots and rhizomatic leaves alternating when sympodial (Heterozostera) with 4-10 vascular bundles...

Post Pollination Pollen Tubes Embryonic and Seedling Development

As in other angiosperms, following the transfer of pollen to stigma, the pollen germinates and a pollen tube grows through the stigma, style, and locule to the micropyle of the ovule where it penetrates the synergid cells (e.g. Raven et al., 1999 Kuo and den Hartog, Chapter 3). The pollen tube facilitates the transfer of sperm cells that fertilize the egg cell and the endosperm nucleus. As indicated above, post-pollination processes are complicated in seagrasses by the complete submergence of...

Root Anatomy and Ultrastructure

The root tip of all seagrasses has a distinct root cap protecting meristematic cells, which provides a continuous set of dividing cells. The mature region may bear root hairs depending on the species and overlying cortical parenchymatous tissues, which enclose air lacunae and a central stele. However, the details of root anatomy may be different among seagrass groups reflecting their root morphology and the substratum. On the outer-most layer, the epidermal cells usually have thin, unlignified...

Secondary Metabolites and Chemotaxonomy

In addition to the ubiquitous sucrose, glucose and fructose, plus two trisaccharides apparently restricted to Phyllospadix spp., several seagrasses accumulate considerable amounts of another type of soluble carbohydrate, inositols. Of the nine possible inositols, only 5 are known to occur in plants and only myo-, l-chiro-, muco- and an 0-methyl-muco-inositol occur in seagrasses. Drew 1984 reviewed current knowledge of the possible roles of the inos-itols and their several methyl esters found in...