BRANCHED STRUCTURES: THE OCCURRENCE, MORPHOLOGY
AND FUNCTION OF TREE-LIKE SYSTEMS

by Gerald Oster
Mount Sinai School of Medicine of the City University of New York

Abstract

A tree in the botanical sense is a branching system designed to provide

the greatest sunlight exposure of the leaves and to provide transport sys-
tems for water and nutrients between the soil and the leaves. The form

of the tree and its roots is determined by genetic and environmental fac-
tors. The vascular system in plants has its counterpart in animals. The
arterial systemsin humans have specialized substructures which help, among
other things, to control temperature and to promote reproduction. Malfunc-
tioning of the arterial system is the principal cause of death among humans.
The bronchial system (a tree with 30 generations of bifurcations) is unique-
ly designed for the transport and exchange of gases. The most complex for-
est of trees is the neural system of the cerebral cortex of man. The devel-
opment and elaboration of the neural system, especially the details of
branching of the dendrites and the distribution of spines, is governed by
factors which have their analogies in botany.

The largest tree system on earth is the Amazon River basin. Theories of
rivers, particularly as regards flow pattern, optimalization, drainage and
hierarchy have their analogies in living systems. The smallest tree system
is a simple hydrocarbon. A. Cayley a century ago enumerated the isomers of
octane. General methods have been worked out for more elaborate molecules.
Branched moleculee* have different chemical reactivities and physical prop-
erties from linear molecules. This is of importance in combustion engineer
ing (the anti-knock problem) and in the metabotism of stored carbohydrates
(the diabetes problem). Stylized (Christmas tree) branching occurs in the
RNA transcription required for protein synthesis and in the dendritic
growth of crystals.

Tree-like systems can be conceptual as with the geneological tree or with
the phylogenetic tree. The former is only rarely a tree. The phylogenetic
tree, in its modern form (e.g., the evolution of amino acid sequence in the
Phylogeny of hemoglobins), is the weighted binary decision-making tree of
the computor programmer.

Gerald Oster is Professor of Biophysics at the Mount Sinai School of Medi-
cine. He is the author of some 200 scientific papers mainly in the fields
of molecular optics, physical biochemistry and human reproduction. He is

a founder of the science of moiré patterns and his moiré constructions have
been shown in many art museums in the USA and abroad.