Chapter 3
Seagrass Morphology, Anatomy, and Ultrastructure
J. Kuo
∗
Centre for Microscopy and Microanalysis, M010, The University of Western Australia,
35 Stirling Highway, Crawley, Western Australia 6009, Australia
C. den Hartog
Zevenheuvelenweg 50, 6571 CK, Berg en Dal, The Netherlands
I. Introduction
Seagrasses possess similar organs and tissues as
the other flowering plants. Nearly all-mature flowering plants have distinctive above and below ground
parts. The exceptions are some pleustophytes such
as the Lemnaceae and representatives of the genus
Ceratophyllum, and haptophytes such as the Podostemaceae. Below ground parts normally consist
of roots for anchoring and rhizomes/stems for mechanical support. Above ground parts usually constitute shoots bearing several leaves. A leaf usually
has a basal sheath for protecting the apical meristem
and developing leaves, and a distal blade for producing food by photosynthesis and giving off water vapor through transpiration. All organs consist
of three basic tissues with a different structure and
function: (a) The epidermis forms a continuous layer
on the surface of the plant body and has a cuticle on
the outer wall to provide mechanical protection, and
restricting transpiration and aeration; (b) The vascular bundle contains the phloem for solute translocation and the xylem for water transport; (c) The
parenchyma tissue with thin walls and non-lignified
collenchyma is responsible for photosynthesis and
storage and the thick walled lignified sclerenchyma
acts as a mechanical support. An air space system
allows movement of gases through the plant. During the reproductive period, flowering plants produce
flowers for pollination and fertilization and then to
set seeds to complete their life cycles.
*Author for correspondence, email: jjskuo@cyllene.uwa.edu.au
In contrast to terrestrial monocotyledons, seagrasses have to live in marine or highly saline
environments, and this has profoundly influenced
their morphology and anatomy. This chapter will examine how tissues and organs of these unusual plants
in both vegetative and reproductive phase have been
modified to allow them to complete their life cycle
in the marine environment.
Sauvageau (1890, 1891) provided the first basis for our understanding of the vegetative anatomy
of seagrasses through excellent descriptions and illustrations. Arber (1920) surveyed the older morphological and anatomical literature of aquatic
plants and Sculthorpe (1967) further advanced the
knowledge of the ecology and biology of herbaceous aquatic plants. den Hartog (1970) established the boundary of modern seagrass taxonomy
with precise morphological characters. Tomlinson
(1982) reviewed old literature and further documented general morphology, detailed anatomy of
vegetative organs and sometimes also reproductive
structures in each genus of the helobian monocotyledons, including seagrasses. He also specifically
discussed leaf morphology and anatomy in relation to taxonomy in seagrasses (Tomlinson, 1980).
Kuo and McComb (1989) provided a review of the
structure and function, mainly of vegetative organs by combining morphological, anatomical and
ultrastructural data. McConchie and Knox (1989a)
added similar information on reproductive biology
and pollination in seagrasses. The earlier morphological and anatomical scientific data which have
been discussed previously (e.g. Tomlinson, 1982;
Kuo and McComb, 1989; McConchie and Knox,
51–87.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp.
c
2006 Springer. Printed in the Netherlands.
Seagrass Morphology, Anatomy, and Ultrastructure
J. Kuo
∗
Centre for Microscopy and Microanalysis, M010, The University of Western Australia,
35 Stirling Highway, Crawley, Western Australia 6009, Australia
C. den Hartog
Zevenheuvelenweg 50, 6571 CK, Berg en Dal, The Netherlands
I. Introduction
Seagrasses possess similar organs and tissues as
the other flowering plants. Nearly all-mature flowering plants have distinctive above and below ground
parts. The exceptions are some pleustophytes such
as the Lemnaceae and representatives of the genus
Ceratophyllum, and haptophytes such as the Podostemaceae. Below ground parts normally consist
of roots for anchoring and rhizomes/stems for mechanical support. Above ground parts usually constitute shoots bearing several leaves. A leaf usually
has a basal sheath for protecting the apical meristem
and developing leaves, and a distal blade for producing food by photosynthesis and giving off water vapor through transpiration. All organs consist
of three basic tissues with a different structure and
function: (a) The epidermis forms a continuous layer
on the surface of the plant body and has a cuticle on
the outer wall to provide mechanical protection, and
restricting transpiration and aeration; (b) The vascular bundle contains the phloem for solute translocation and the xylem for water transport; (c) The
parenchyma tissue with thin walls and non-lignified
collenchyma is responsible for photosynthesis and
storage and the thick walled lignified sclerenchyma
acts as a mechanical support. An air space system
allows movement of gases through the plant. During the reproductive period, flowering plants produce
flowers for pollination and fertilization and then to
set seeds to complete their life cycles.
*Author for correspondence, email: jjskuo@cyllene.uwa.edu.au
In contrast to terrestrial monocotyledons, seagrasses have to live in marine or highly saline
environments, and this has profoundly influenced
their morphology and anatomy. This chapter will examine how tissues and organs of these unusual plants
in both vegetative and reproductive phase have been
modified to allow them to complete their life cycle
in the marine environment.
Sauvageau (1890, 1891) provided the first basis for our understanding of the vegetative anatomy
of seagrasses through excellent descriptions and illustrations. Arber (1920) surveyed the older morphological and anatomical literature of aquatic
plants and Sculthorpe (1967) further advanced the
knowledge of the ecology and biology of herbaceous aquatic plants. den Hartog (1970) established the boundary of modern seagrass taxonomy
with precise morphological characters. Tomlinson
(1982) reviewed old literature and further documented general morphology, detailed anatomy of
vegetative organs and sometimes also reproductive
structures in each genus of the helobian monocotyledons, including seagrasses. He also specifically
discussed leaf morphology and anatomy in relation to taxonomy in seagrasses (Tomlinson, 1980).
Kuo and McComb (1989) provided a review of the
structure and function, mainly of vegetative organs by combining morphological, anatomical and
ultrastructural data. McConchie and Knox (1989a)
added similar information on reproductive biology
and pollination in seagrasses. The earlier morphological and anatomical scientific data which have
been discussed previously (e.g. Tomlinson, 1982;
Kuo and McComb, 1989; McConchie and Knox,
51–87.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp.
c
2006 Springer. Printed in the Netherlands.