As the role of ecological parameters in genotype characterization is growing, particularly in connection with potential climate change, their qualitative description should be transformed into quantitative one. The latter became possible owing to development of phytotronics and computing machines, which enable multifactor planned experiments based on the systems approach. The results of such experiments can be represented in the form of regression equations establishing the relationship between the plant response and the factors used in the experiment as variables. Since net photosynthesis is highly sensitive to the ambient environment, the values of the factors at which net photosynthesis is optimal can be regarded as ecological characteristics of the ecotype (variety) at a specific phase of its development.