Page 100 - Algae Anatomy, Biochemistry, and Biotechnology

Anatomy 83

FIGURE 2.56 Root system of Bigelowiella natans (Chlorarachniophyta). F1, main flagellum; BBB, barren
basal body; R1, R2, R3, and R4, microtubular roots.

The microtubular rootlets of the flagellate reproductive cells of Ulvophyceae follow the X-2-
X-2 arrangement of most green algae, with X ¼ 4in Ulva and Enteromorpha, and X ¼ 5in
Ulothrix. Striated bands connect the rootlets to the basal bodies, which are connected anteriorly
by an upper connective; in some genera, additional striated bands between the basal bodies and
striated component associated with the two-membered root can be detected.
Members of the Cladophorophyceae generally conform to the X-2-X-2 system, with X ¼ 3in
Chaetomorpha and X ¼ 4in Cladophora. The microtubular rootlet system of the biflagellate cells
extend posteriorly nearly parallel to one another and to the basal body from which they arise. In the
X-membered rootlets, an electron-dense strut or wing connects one of the uppermost microtubules
to the subtending singlet, and the entire rootlet is usually subtended by a massive, more or less
striated structure. Also the two-membered rootlets may be accompanied by such structures. An
upper transversely striated connective links the basal bodies.
The flagellar apparatus of the reproductive cells of the Bryopsidophyceae is anchored in the cell
by four microtubular roots following the usual X-2-X-2 pattern. Each of the microtubules in the
rootlet may be subtended by an electron-dense wing. The basal bodies are connected anteriorly
by a non-striated upper connective, with a typically pronounced arched appearance. Transversely
striated bands connecting the rootlets to the basal bodies are also present. Species exist in this
class, which produce stephanokont zoospores with more than 30 flagella. In these cells, the basal
bodies are connected by a non-striated fibrous upper ring, which can be considered the result of
the fusion of many non-striated upper connectives. The proximal ends of the basal bodies are par-
tially enclosed in a second lower ring of amorphous material. Four- and six-membered microtubular
roots depart from between the basal bodies.
No flagellate reproductive cells are present in the Zygnematophyceae.
The microtubular root system of the Trentepohliophyceae motile cells (tetraflagellate zoospores
and biflagellate gametes) do not follow the X-2-X-2 pattern, but show a 6-4-6-4 arrangement in
Trentepohlia sp. The dorsiventrally compressed form of the flagellate cells forces the basal
bodies and the root system components in a flattened arrangement. Basal bodies are aligned perpen-
dicular to the long axis of the cell, with a parallel or antiparallel arrangement, and the microtubular