Preface Computer models that treat plants as consisting of elementary units have become increasingly popular. The core of such a model is the description of what happens in a single plant element.
Models can use various elements, such as bud, leaf, internode, stem segment, etc.
A computer program takes care of all the elements and integrates their activities to the functioning of the whole plant. Both the 3-D architecture and the metabolic processes can be treated in the same model at the same time in a natural way. Increasing speed of computers, developing programming tools and available mathematical techniques have made the construction of such models increasingly feasible. Modelling plants using computer models where the plant consists of elementary units can be viewed as an extension of the classical method of differential calculus. The difference in comparison with analytical solutions of differential equations is the immensely greater capacity of the computer to deal with complex situations.