Chapter 3 Seagrass Morphology, Anatomy, and Ultrastructure
53
Fig. 1. General morphology of seagrasses. A. Enhalus acoroides. Scale = 3 cm. B. Halophila engelmanni. Scale = 3 mm. C. Halophila
minor. Scale = 2 cm. D. Zostera asiatica. Scale = 15 cm. E. Posidonia sinuosa. Scale = 3.5 cm. F. Halodule uninervis. Scale = 2.5 cm.
G. Cymodocea serrulata. Scale = 5 cm. H. Syringodium isoetifolium. Scale = 4.5 cm. I. Thalassodendron pachyrhizum. Scale = 4 cm.
Posidonia and Syringodium whose roots are thin and
lignified (Fig. 3A), but cell walls in the hard roots
of Thalassodendron and Amphibolis are thickened
and lignified. Inside the epidermis, there is a distinct exodermis of one or more cell layers, each of
which has thickened but unlignified walls containing
suberin lamellae (Fig. 3C) (see Kuo and McComb,
1989; Kuo, 1993b). Exodermal cells in roots of Thalassodendron and Amphibolis are thickened and lignified (Kuo, 1983). Barnabas (1994b, 1996) showed
that the Casparian strip-like structure of the exodermis was also present in other aquatic plants including the seagrass genera Zostera (Fig. 2I), Halodule (Fig. 3B), Halophila, the brackish-water genus
Ruppia, and even the freshwater species of Potamogeton and Nymphaea. The exodermal cells abutting root hairs of Zostera capensis (Barnabas and
Arnott, 1987) show the characteristics of transfer
cells (Gunning and Pate, 1969; Gunning, 1972; Pate
and Gunning, 1972). In contrast, walls between
53
Fig. 1. General morphology of seagrasses. A. Enhalus acoroides. Scale = 3 cm. B. Halophila engelmanni. Scale = 3 mm. C. Halophila
minor. Scale = 2 cm. D. Zostera asiatica. Scale = 15 cm. E. Posidonia sinuosa. Scale = 3.5 cm. F. Halodule uninervis. Scale = 2.5 cm.
G. Cymodocea serrulata. Scale = 5 cm. H. Syringodium isoetifolium. Scale = 4.5 cm. I. Thalassodendron pachyrhizum. Scale = 4 cm.
Posidonia and Syringodium whose roots are thin and
lignified (Fig. 3A), but cell walls in the hard roots
of Thalassodendron and Amphibolis are thickened
and lignified. Inside the epidermis, there is a distinct exodermis of one or more cell layers, each of
which has thickened but unlignified walls containing
suberin lamellae (Fig. 3C) (see Kuo and McComb,
1989; Kuo, 1993b). Exodermal cells in roots of Thalassodendron and Amphibolis are thickened and lignified (Kuo, 1983). Barnabas (1994b, 1996) showed
that the Casparian strip-like structure of the exodermis was also present in other aquatic plants including the seagrass genera Zostera (Fig. 2I), Halodule (Fig. 3B), Halophila, the brackish-water genus
Ruppia, and even the freshwater species of Potamogeton and Nymphaea. The exodermal cells abutting root hairs of Zostera capensis (Barnabas and
Arnott, 1987) show the characteristics of transfer
cells (Gunning and Pate, 1969; Gunning, 1972; Pate
and Gunning, 1972). In contrast, walls between