In the article on the basis of the analysis of providing the population of the world with food, the task of creation of small-sized intellectual devices for express systems of control of conditions of development of food plants is set. Such control can be carried out both in laboratory conditions and in the on-line mode. The authors analyzed the known methods of tissue diagnostics of plants by sap, by lymph, by extract, etc. The methods used in the laboratory, first of all, as one of the advanced ones on the simulation of cellular modeling of photosynthesis in plant tissues are considered. Portable intelligent devices based on the method of chlorophyll fluorescence were created, its functional scheme was developed and a working model was developed, an application software package was developed. This allows on-line control of the impact on plants of stress factors, frost, drought, dehydration, the level of soil fertilizers, herbicides, biological additives, environmental pollution by harmful emissions, viral and bacterial loads. The effectiveness of research is shown.