Sensitive Growth Grammars
Sensitive growth grammars form an extended variant of L-systems.
They were defined by Winfried Kurth and implemented in the software
GROGRA. Their definition was guided
by the fact that the pure L-systems formalism cannot cope properly
with the representation of the great variety of plant architecture
and growth behaviour. The new features include:
- Global Sensitivity
- Global sensitivity means a dependence of growth on the overall
structure and not only on neighbouring elements. Examples are
- the dependence on orientation: Plant growth is influenced by
the directions of gravity (geotropism)
and light (phototropism).
- the dependence on density: Plant parts cannot penetrate obstacles
such as, e.g., other plant parts or walls; instead, they have to bypass
the obstacle by deviating growth movements.
- the dependence on light: Besides the orientation of light,
its mere availability is important. This is influenced by
overshadowing by other plant parts and obstacles.
- Local Variables
- Local variables can be attached to elements of the growing
structure. They may represent local properties like
carbon or nutrient pools.
- Tree Calculations
- Tree calculations perform arithmetics on the subtree emerging
out of a given element. Such a calculation may determine the
total length or mass of a subtree, and these values in turn
may have an influence on the further growth of a plant.