Until the middle of the 20th century, plant roots were of very little interest to the arts and sciences: just like painters, botanists focused on the visible parts of plants. From the beginning of the 19th century, however (at least in France), writers showed a real fascination for roots - more horrified than admiring. In the first half of the 20th century, no doubt influenced by the birth of abstract art, visual artists began to approach them less as forms to be tamed than as processes to be deciphered or transposed. Some of these processes, which nowadays arouse immense interest among many botanists and philosophers, are examined here from both a scientific and an artistic point of view: rooting; the transition in a tree between the unicity of the trunk and the multiplicity of roots; the interconnection of roots among themselves and with various symbionts. The last part is devoted to the relationship between roots and various modalities of thought: on the one hand, the dreams that roots inspire to artists and poets, and on the other hand, the theories and reflections that they arouse today in certain scientists, writers and philosophers.
Plasticity is a fundamental property of the matter, among which the self-folding or the adaptability reflect some laws inherent to the mechanical behaviour of materials, space-time geometry, biochemical processes or morphogenesis at the interface between developmental biology and physics. Contrarily to elasticity, it does not, however, limits itself to it, dressing a high predictive value of the dynamic behaviour of complex systems, what makes it a founding, and not only an emergent or purely systemic property of the matter and the evolution of living systems. Matter-form complexes from which folds are expressions are then defined as aggregates of bound couples directly acting at the anchor of irreducible dimensions or expressions by including the subject in the plasticity of the world.
The geometric analysis of a drawing representing the profile of a man’s head gives us a glimpse of how Leonardo established his constructive approach to profiles from a first form. The geometric analysis of three other Leonardo profiles confirms this approach. It is with this same approach that Leonardo produced his five female portraits.