The theme of article is closely connected to problems of construction of applied simulation models of crops productivity. In article the basic groups of methods and approaches to mathematical modelling of regulation processes in plants physiology - processes of growth and phenologic development of plants - are resulted. The short description and the qualitative analysis of some the models being the most typical representatives of the basic classes of models of growth and development of plants are presented. On the basis of comparison of described models is summarized, what optimal schema of management of regulation processes of plants is found as a result of application of variational approach.