In spite of its simplicity, the simple model of a compound
leaf shown in
properly reflects one of the general principles of the development of higher
It is called the principle of subapical growth,
and means that only apices can create new branches. Internodes may elongate,
but cannot initiate branches. These rules are illustrated schematically
A variety of structures can be produced
through subapical growth, depending on which apices remain active and initiate
new branches, and which ones do not. In line with the research interests
of Lindenmayer and other biologists using L-systems, this section focuses
on the modeling and simulation of the inflorescences of herbaceous plants.
For a more complete description see Chapter 3 of [Pru1990]
The simplest case occurs when only the apex of the main
axis of the growing plant produces new branches, as shown in
These lateral branches carry buds and
then flowers, but do not branch any further. The resulting structure is
called a monopodial branching structure, and the corresponding
inflorescence is called a raceme.
development of a common weed Capsella bursa-pastoris, or shepherd's
purse, following this principle.
The creeping bellflower Campanula rapunculoides,
develops in the same manner.
Additional views of this development are included in
which combines models of several plants in a single scene, and
which presents a view of the flowers.
shows a form of branching
which, in a sense, is opposite to the previous one. In this case, called
sympodial branching, the apex produces a flower bud terminating
the development of the current axis, but in addition produces one or more
active lateral apices. This process repeats recursively, with the main thrust
of the development always going into the lateral branches.
The resulting inflorescence type is called a cyme.
The development of Lychnis coronaria, or rose campion, shown in
provides a good example of the described process.
presents a view of the development of a single flower.
Yet another branching type, called polypodial
branching, is presented schematically in
In this case, both the apex of the main
axis and the lateral apices produce new branches until, at some point in
time, the apices undergo a developmental switch and are transformed into
flower buds. The resulting inflorescence, called a panicle, may
adopt various forms depending on the geometric parameters.
Plate 19) shows a so-called decussate
branching pattern, in which pairs of lateral branches are arranged in mutually
By terminating each of these branches with a flower we
can model lilac inflorescences, as presented in