31. Schnepf, E. and R. M. Brown, Jr. 1971.
On relationships between endosymbiosis and the origin of plastids
and mitochondria. IN: Origin and Development of Cell Organelles
(Ursprung and Reinert, eds.). Springer-Verlag.
31. Introduction
In 1883 SCHIMPER wrote in a footnote: "Sollte es sich definitiv bestatigen, dass die Plastiden in den Eizellen nicht neu gebildet werden, so wurde ihre Bezie-hung zu dem sie enthaltenden Organismus einigermassen an eine Symbiose erinnern. Moglicherweise verdanken die grunen Pflanzen wirklich einer Vereinigung eines farblosen Organismus mit einem von Chlorophyll gleichmassig tingierten ihren Ursprung."
A similar hypothesis on the evolution of
the cells of higher organisms from endosymbiontic associations
of different "bioblasts" was expressed by ALTMANN (1890).
In the past, ideas on the evolution of plastids and mitochondria
were based on a poor knowledge of the organelles themselves.
Therefore, the hypothesis of SCHIMPER and ALTMANN was accepted
(e.g. by MERESCHKOWSKY, 1905), rejected (BUCHNER, 1953; KLEIN
and CRONQUIST, 1967) though convincing facts for the interpretations
were lacking (GEITLER, 1923), or it was ignored. Presently, there
are many new lines of evidence which allow us to view these interpretations
in a new context. Obviously, it is extremely difficult to present
direct evidence for the evolution of plastids and mitochondria.
The following remark depicts the current situation: "Indeed,
it is hard to see how it would be possible to be sure of the correctness
of a hypothesis like that ... But even if in the long run it should
turn out that the hypothesis of the exogenous origin is a March
hare, the chase should be stimulating and illuminating" (Anonymous,
1967). The idea of exogenous origin already has influenced several
new proposals on the phylogeny and the classification of higher
organisms (SAGAN, 1967; MARGULIS, 1968; WHITTAKER, 1969). All
ideas on the origin of plastids and mitochondria must take into
account that they are absent in prokaryotes and that they never
arise de novo but by division. This last statement is
the result of many morphological, genetic and biochemical studies
which are summarized in this volume by STUBBE and BAXTER.