Sustainable plant development, i.e. maintenance of its phenotype in conditions of changing environmental parameters or genetic deviations, is realized by a set of mechanisms, generally characterized by developmental stability. The most striking manifestation of the stability of the development of the biological object at the macro level is the effect of fluctuating asymmetry (FA). The lighting conditions, along with other environmental factors, affect both the productivity of the plant and the stability of its development. The issues that remain scarcely studied are the influence of lighting conditions and plant variety on the FA level. One of the widely used and informative parameters is the chlorophyll content in plant leaves and their size. The aim of the study is to confirm the hypothesis of the effect of differences in the light quality and plant variety on the level of FA of the symmetrical plant structures. The object of the study is the leaves of tomato plants grown in an industrial greenhouse. The measurements were carried out in the greenhouse of Mezvidi, Latgalia, for three variants: tomato variety orange Bolzano F1 grown under high-pressure sodium lamps (HPS) and LED sources, and the red Encore F1 grown under HPS. As a result of the experiments, the presence of a significant asymmetry of the bilateral structures of tomato leaves was detected by their size and chlorophyll content. The fluctuating nature of asymmetry is proved. It was revealed that the influence of the type of the light source and tomato variety on FA on the basis of certain traits is multidirectional. For the tomato variety Bolzano, the level of FA on the basis of the leaflet size is 66 % higher under HPS compared to the LED, and on the basis of the chlorophyll content does not depend on the type of the light source. For HPS the level of FA on the basis of the leaflet size is 24 % higher at Bolzano compared to Encore, and on the basis of the chlorophyll content, it is 28 % lower.