Spoken text

The growth of plants and thus the structures resulting from growth are often dependent on specific information from other plant parts. This may, for example, be hormone signals, energy flows or the availability of certain substances. To model such influences with L-systems, the concept of context-sensitive L-systems was developed. Assuming that the relevant information comes from the vicinity of an object, the application of a particular rewriting rule depends on the predefined context surrounding the object. This context is specified on the left-hand side.
To illustrate this, we will look at a relatively simple example. But its principles can be applied to more complex functional and structural models.
Two modules are declared, where the module A has the meaning of a meristem, which is not displayed as a visible object. The only parameter of the module is its age.
Out of this a branch grows with length 10 and color green. In addition, the age increases in the first four steps by 1. When the age reaches 5, only a red branch segment is created and the length growth stops. In the next rule the context awareness is applied, which can be recognized by the star in connection with round brackets. A green branch segment is replaced by a red segment if on the right side of this segment, this means geometrically above, is a red segment.
The final rule, which is applied parallel to context sensitivity, eventually replaces every red segment by a blue one with a long yellow side branch randomly arranged around the head axis.
By this context sensitivity a downward directed and branch-inducing signal is simulated. It is clear that also transport processes within a plant may be simulated by using such a context.
In addition, by the arrangement of the context on the left-hand side one can determine in which 'neighborhood' the context has to be true. For a better understanding of this relationship you should look at the two examples of the left-hand and right-hand context more closely.