NON-FILAMENTOUS AQUATIC FUNGI
87
like fashion, we will not know if these differences are of generic and/or
functional significance. On the other hand, we have not established the
method of origin of the single large mitochondrion in the spores of
Blastocladiella.
We would very much like to know, for instance, if it
results from the coalescence of two or more smaller mitochondria
present in the multinucleate protoplast of the parent sporangium or if,
instead, the fungus simply has fewer but larger mitochondria. If the
latter were the case, it would imply an unusual one-to-one relationship
between nuclei and mitochondria.
This brief review reveals the great deficiency in our knowledge of
spore formation. But, despite the many gaps, it is evident that this stage
in the life-cycle provides numerous and fascinating problems for any
experimental morphologist. By what forces, for example, does the
ribosomal material become localized into a nuclear cap? What mechanism
establishes the position of the mitochondrion and its associated flagellum
and lipid granules? What, in particular, incites cytokinesis in the absence
of karyokinesis, and how is it managed? When and how, precisely, is the
sudden increase in the enzymatic and respiratory machinery triggered
off? The cell accomplishes all of these things in a remarkably short
period of time—about 30 minutes for the OC cell and some 2 hours for
the RS cell. Our problem, then, is to elucidate the mechanisms by which
the organization and co-ordination of these important structural and
functional components is achieved. Considerable synthetic activity must
occur during the construction of the macromolecular and supramolecular
structures encountered in the zoospores. To pin down these operations,
and to localize them, will require the full battery of modern analytical
techniques.
IV. Summary
If anything can be said to constitute, in the near future, a major wave
in biology, studies of the synthesis, maintenance, and functions of
organized heterogeneity among cells and tissues of plants and animals
will no doubt contribute the flood, sans pareil, of the next few decades !
Although the problem is superbly tricky and elusive, recent years have
seen it yield some footholds—as slippery as they may still be. Biologists
have often recognized, for instance, that the system of interrelated units
found in any multicellular organism can, to some extent, be likened to a
clone of cells produced by a micro-organism growing on some solid
substratum. If the notion has validity, then it follows that the differentiation of cells in a multicellular organism may have important things in
common with the variations exhibited within a micro-organismal clone.
Analyses of the latter type of system may thus provide the kinds of
D
87
like fashion, we will not know if these differences are of generic and/or
functional significance. On the other hand, we have not established the
method of origin of the single large mitochondrion in the spores of
Blastocladiella.
We would very much like to know, for instance, if it
results from the coalescence of two or more smaller mitochondria
present in the multinucleate protoplast of the parent sporangium or if,
instead, the fungus simply has fewer but larger mitochondria. If the
latter were the case, it would imply an unusual one-to-one relationship
between nuclei and mitochondria.
This brief review reveals the great deficiency in our knowledge of
spore formation. But, despite the many gaps, it is evident that this stage
in the life-cycle provides numerous and fascinating problems for any
experimental morphologist. By what forces, for example, does the
ribosomal material become localized into a nuclear cap? What mechanism
establishes the position of the mitochondrion and its associated flagellum
and lipid granules? What, in particular, incites cytokinesis in the absence
of karyokinesis, and how is it managed? When and how, precisely, is the
sudden increase in the enzymatic and respiratory machinery triggered
off? The cell accomplishes all of these things in a remarkably short
period of time—about 30 minutes for the OC cell and some 2 hours for
the RS cell. Our problem, then, is to elucidate the mechanisms by which
the organization and co-ordination of these important structural and
functional components is achieved. Considerable synthetic activity must
occur during the construction of the macromolecular and supramolecular
structures encountered in the zoospores. To pin down these operations,
and to localize them, will require the full battery of modern analytical
techniques.
IV. Summary
If anything can be said to constitute, in the near future, a major wave
in biology, studies of the synthesis, maintenance, and functions of
organized heterogeneity among cells and tissues of plants and animals
will no doubt contribute the flood, sans pareil, of the next few decades !
Although the problem is superbly tricky and elusive, recent years have
seen it yield some footholds—as slippery as they may still be. Biologists
have often recognized, for instance, that the system of interrelated units
found in any multicellular organism can, to some extent, be likened to a
clone of cells produced by a micro-organism growing on some solid
substratum. If the notion has validity, then it follows that the differentiation of cells in a multicellular organism may have important things in
common with the variations exhibited within a micro-organismal clone.
Analyses of the latter type of system may thus provide the kinds of
D