Chapter 3 Seagrass Morphology, Anatomy, and Ultrastructure
59
A
B
D
C
E
F
G
H
Fig. 5. Anatomy of rhizome internodes (A, B) and sheaths (C–H). A, B. Posidonia australis. Walls of the rhizome epidermal (E) and
exodermal (Ex) cells are lignified and autofluorescent, a few tannin cells (T) occur in the cortical tissue (C). Scales = 50 µm. C. Zostera
marina. Several large air lacunae (A) occur between two sheath longitudinal vascular bundles (V). Scale = 250 µm. D. Posidonia
kirkmanii. Numerous smaller lacunae (A) occurring in the entire mesophyll tissues even near the longitudinal vascular bundle (V). Note
that large fiber bundles (F) occur near the adaxial epidermal cells. Scale = 400 µm. E. Posidonia australis. Fibre cells (F) occur in the
mesophyll tissue (M) near the adaxial epidermal cells (E) and walls of fiber cells are lignified. Scale = 50 µm. F. Posidonia australis.
A thin, uniform electron transparent cuticle (arrows) and the outer tangential wall of the epidermal cell (E) has outer (OW) and inner
(IW) regions. Scale = 1 µm. G. Phyllospadix scouleri. The adaxial sheath epidermal cell contains a nucleus (N), several chloroplasts
(C), mitochondria (M), vacuoles (V) and wall ingrowths. Scale = 2 µm. H. Phyllospadix scouleri. The abaxial sheath epidermal cell
contains a large central vacuole (V) and a few small plastids (C). The cuticle appears as a thin electron transparent layer (arrow), and
the wall has outer wall (OW) and inner wall (IW) regions. Scale = 1 µm.
there is plenty of ‘marine fiber’ from leaf sheath
remains deposited on the ocean floor. However,
Davies (1970, Fig. 12) illustrated a tidal channel
on the Wooramel Bank on the eastern margins
of Shark Bay about 3 m deep cutting through
Posidonia rhizome mesh (termed rhizome and root
mesh) and deposits under living seagrass reached
a maximum thickness of more than 7 m. The rhizomes of Thalassodendron ciliatum appear also
to be very persistent forming extensive mats. As
the decomposition of the material is very slow,
these mats can attain a considerable thickness. Lipkin (1988) found living rhizomes up to 25 cm
down in the mat, although it was very difficult to
59
A
B
D
C
E
F
G
H
Fig. 5. Anatomy of rhizome internodes (A, B) and sheaths (C–H). A, B. Posidonia australis. Walls of the rhizome epidermal (E) and
exodermal (Ex) cells are lignified and autofluorescent, a few tannin cells (T) occur in the cortical tissue (C). Scales = 50 µm. C. Zostera
marina. Several large air lacunae (A) occur between two sheath longitudinal vascular bundles (V). Scale = 250 µm. D. Posidonia
kirkmanii. Numerous smaller lacunae (A) occurring in the entire mesophyll tissues even near the longitudinal vascular bundle (V). Note
that large fiber bundles (F) occur near the adaxial epidermal cells. Scale = 400 µm. E. Posidonia australis. Fibre cells (F) occur in the
mesophyll tissue (M) near the adaxial epidermal cells (E) and walls of fiber cells are lignified. Scale = 50 µm. F. Posidonia australis.
A thin, uniform electron transparent cuticle (arrows) and the outer tangential wall of the epidermal cell (E) has outer (OW) and inner
(IW) regions. Scale = 1 µm. G. Phyllospadix scouleri. The adaxial sheath epidermal cell contains a nucleus (N), several chloroplasts
(C), mitochondria (M), vacuoles (V) and wall ingrowths. Scale = 2 µm. H. Phyllospadix scouleri. The abaxial sheath epidermal cell
contains a large central vacuole (V) and a few small plastids (C). The cuticle appears as a thin electron transparent layer (arrow), and
the wall has outer wall (OW) and inner wall (IW) regions. Scale = 1 µm.
there is plenty of ‘marine fiber’ from leaf sheath
remains deposited on the ocean floor. However,
Davies (1970, Fig. 12) illustrated a tidal channel
on the Wooramel Bank on the eastern margins
of Shark Bay about 3 m deep cutting through
Posidonia rhizome mesh (termed rhizome and root
mesh) and deposits under living seagrass reached
a maximum thickness of more than 7 m. The rhizomes of Thalassodendron ciliatum appear also
to be very persistent forming extensive mats. As
the decomposition of the material is very slow,
these mats can attain a considerable thickness. Lipkin (1988) found living rhizomes up to 25 cm
down in the mat, although it was very difficult to