Biology Reference
In-Depth Information
bryophytes, as well as in charophytes, pteridophytes and gymnosperms, but
not in angiosperms (
Matsunaga et al., 2004; Popper and Fry, 2004
).
Some bryophytes show the presence of specialized water-conducting cells,
where the cytoplasmic content has been removed, and so water transport is
facilitated. It should be pointed out that water-conducting cells in bryophytes
may have evolved independently (
Ligrone et al., 2000
). There are not many
data to assure the presence of actual lignin in the cell walls of bryophytes.
However, the occurrence of lignin-like compounds in bryophytes has been
widely described (
Delwiche et al., 1989
).
Liverworts are usually regarded as the most basal group in bryophytes.
Among them, Marchantiales and Jungermanniales have no water-conduct-
ing cells (
H
´
bant, 1977; Kobiyama and Crandall-Stotler, 1999; Ligrone et al.,
2000
). However, an internal strand of water-conducting cells is present in
Calobryales and Metzgeriales (
Burr et al., 1974; H
´
bant, 1977; Ligrone et al.,
2000
). In this case, these specialized cells are dead and contain no cytoplas-
mic components, with cell walls containing pores derived from plasmodes-
mata (
Ligrone et al., 2000
). In Metzgeriales, the water-conducting cells show
thick cell walls with helicoidal pits, reminiscent of tracheids. However,
homology between the two types is highly unlikely because of their different
developmental programme (
Ligrone et al., 2000
). Liverworts are reported to
contain polyphenolic compounds as they show autofluorescence under UV
light (
Graham et al., 2004
).
Ligrone et al. (2008)
reported the presence of
guaiacyl-syringyl lignin in bryophytes, using immunocytochemical detec-
tion. Antibodies against G and GS synthetic lignin-like polymers strongly
labelled compounds not only from tracheophytes but also from bryophytes
such as liverworts and mosses. In the case of liverworts, a stronger signal for
GS lignin was labelled in Marchantia polymorpha and Conocephalum con-
icum. It has been established that syringyl lignin occurs in M. polymorpha,a
liverwort, belonging to terrestrial plants that lack a vascular system, as
discussed above. Specifically, Marchantiales are known to even lack the
central strand of water-conducting cells typical of other bryophytes. Never-
theless, by means of thioacidolysis and nitrobenzene oxidation,
Espi
˜
eira
et al. (2011)
reported a H:G:S ratio of 14:80:6 in M. polymorpha (
Fig. 5
).
Mosses are known to contain specialized water-conducting cells, called
hydroids (
Ligrone et al., 2000
). These cells lack cytoplasmic content and are
highly elongated. The presence of lignin has not been detected, but hydroids
are assumed to contain polyphenols (
Espi˜ eira et al., 2011; Miksche and
Yasuda, 1978; Scheirer, 1980
).
Ligrone et al.(2008)
used anti-lignin labelling to detect lignin in bryophytes.
The signal was stronger in the case of GS lignin antibodies than G lignin ones,
especially in the mosses Sphagnum cuspidatum and Dendroligotrichum
