References

62 T. Sachs
the development of varied biological patterns. The mature stomata of Sansevieria
are more orderly or predictably spaced than the early, reversible
stages of stomata initiation (Kagan and Sachs 1991). “Neural Darwinism”
is a mechanism by which appropriate nerve connections are selected from
excess alternatives (Edelman 1987). Within cells, microtubules are maintained
according to functional roles that are established after they have
been formed (Kirschner and Mitchison 1986).
It may be useful to consider the adaptive significance of the generation
of tree form by developmental selection rather than strict programs. Competition
between branches requires the wasteful development of structures
that are not maintained. There is no doubt that dead branches below trees
represent considerable organic material. Yet these branches did carry out
photosynthesisforaslongastheywereproductiveandresourcessuchas
bound nitrogen can be withdrawn from dying plant organs (Habib et al.
1993). Losses of substrates could be balanced by the advantages of gradual
selection, in which information about the value of an existing branch
feeds back to its survival and further development. This testing of varied
possibilities could provide for a robust outcome.
A major advantage of developmental section may be in its relation to
plasticity. It is possible that in a predictable, ideal world strict programs
could result in superior biological forms. The real world, however, is far
from predictable. In the case of trees, the presence of competing neighbors,
damage due to herbivores and parasites and possible local failures
in the development of the plant itself require a pronounced developmental
plasticity. Developmental selection uses the very same processes and
genetic information to generate form and to insure plastic responses to unpredictable
conditions (Sachs 2002). This parsimony might have adaptive
significance both because simpler developmental systems are required and
because the various component are all optimally integrated.
References
Barlow PW (1989) Meristems, metamers and modules and the development of shoot and
root systems. Bot J Linn Soc 100:255–279
Berleth T, Sachs T (2001) Plant morphogenesis: long-distance coordination and local patterning.
Curr Opin Plant Biol 4:57–62
Cline MG (1994) The role of hormones in apical dominance. New approaches to an old
problem in plant development. Physiol Plant 90:230–237
Edelman GM (1987) Neural Darwinism – the theory of neuronal group selection. Basic
Books, New York
Frank SA (1996) The design of natural and artificial adaptive systems. In: Rose MR, Lauder
GV (eds) Adaptation. Academic, San Diego, pp 451–505
Frank SA (1997) Developmental selection and self-organization. BioSystems 40:237–243