Tree growth and architecture

Levels of organization

When observing a plant we can very easily recognize some of its natural constitutive elements. By the way of its elementary process of growth a plant is made of a succession of nodes.
The set of successive nodes expresses a physical direction which is named an axis.
In many species the edification of an axis is due to a rhythmic process of modes extension. The terminal or apical bud periodically breaks out (in North temperate countries at springtime) and new organs of the leafy stem are expanded. This new stem portion thus elaborated during a continuous extension phase is called a growth unit.
Such rhythmic growth can express many time a growth season period (i.e. a year) : polycyclism . The resulting annual shoot then consists of many growth units (polycyclic shoot).

All these growth expression are traduced by morphological markers on shoots (scales, scars, short internodes, reduced leaves...). The knowledge of such morphological markers is very helpful for biologists and foresters to a posteriori stem analysis.

So a plant appears to result of the addition of many ways of structure observation. There is many levels of organization in the plant structure: we can observe, reveal and use for plant edification understanding (Barthélémy, 1991, Godin & Caraglio, 1998 )

The use of these levels of organization with their associated morphological markers and the methodology to approach plant edification in space and time are synthesized in plant architecture analysis (Hallé et al., 1978, Barthélémy & Caraglio, 1997 ).