Connectance in Sorghum development: beyond the genotype-phenotype duality.

Connectance, the level of linkage between organs, was measured in different lines of Sorghum bicolor during their reproductive development. It was compared with expression of characters, their level of variability and their heritability. A negative relationship is observed between connectance and heritability. Further results indicate that connectance does not simply introduce a noise factor in expression of a pre-existing information, but that it is directly involved in phenotypic expression and plasticity. Connectance appears as partly determined by the nature and dynamics of the network of relationships. It is concluded that the phenotype is not restricted to the deterministic expression of a pre-existing program, the genotype. Morphogenesis also involves another dimension, self-organized, which confers reliability, stability and adaptability to the developmental processes. The complex interactions between these two dimensions and their evolutionary consequences are discussed.