Aim. To study the biological activity of wheat germ agglutinin (WGA) relative to the spring wheat plants under the influence of N-acetyl-D-glucosamine (hapten of WGA, GlcNAc) at pre-sowing treatment of seeds. Methods. Inhibitory analysis as well as physiological (pot experiments, estimation of plants growth and development, wheat grain productivity) and biochemical (chlorophyll a+b content) methods. Results. It was shown in the pot experiments that WGA (100 nM) at the pre-sowing of seeds stimulated the growth processes and the plants vegetative mass formation (shoot mass increased from 10 to 24 % in different ontogenesis phases) as well as the chlorophyll (a+b) accumulation in leaves (from 1.2 to 1.4 times), which led to an increased level of realization of wheat grain productivity (the grain number, weight per plant and 1000 grain weight increased by 26, 26 and 6 % respectively). Hapten of WGA N-acetyl-D-glucosamine (100 mM) inhibited the positive effects of wheat lectin on the plants: from 5 to 19 % (by the vegetative mass), from 0 to 18 % (by the level of green photosynthetic pigments), from 3 to 13 % (by the grain productivity). The maximum inhibitory effect of hapten was noted in the tillering and boot development phases of wheat ontogenesis. Conclusions. The biological activity of WGA at the pre-sowing treatment of spring wheat seeds was expressed in the intensification of plant growth and development, the active accumulation of chlorophyll in leaves, and an increase in the wheat grain productivity. Hapten had a significant reducing effect on the biological activity of wheat lectin resulted in inhibition of positive lectin’s effects on physiological and biochemical parameters of the spring wheat plants development. It is one of the arguments in favour of the lectin nature of these effects.