Introduction Wheat is currently the world’s most important food crop and it has determinative part in Hungarian crop production too (Kutasy et al., 2005). Yield levels of winter wheat were determined mostly by climatic effects of the cropyears limited primarily by water deficiency (Hoffmann-Burucs, 2005), the actual quantity of precipitation prevails in interaction with other external factors (Hoffmann et al., 2006). Light and nutrients are two essential factors that plants must have to grow and forming yield (Csajbok et al., 2005). Among the corns for fertilization one of the most exacting and best reacting is the winter wheat (Szentpetery, 2004). Nitrogen is one of the most important elements in the nutrition of higher plants, wheat grain yields have always been strongly linked to available N nutrition (Szentpetery et al., 2005). Our small grain cereals belongs to C3 plants. This means that their photosynthesis is limited even under the best conditions. Although the correlation between leaves’ photosynthesis and productivity of wheat is not always positive, but under circumstances of arable land the photosynthesis is a factor that defines the higher production potential of genotypes (Pajevic et al., 1999). Reynolds et al., (2000) were measured net photosynthetic rate (An) on wheat cultivars at booting, anthesis and grain filling and found significant correlation between An and grain yield at all developmental stages. Pepo (2005) experiments showed, that the dry matter production and LAI have determined basically the yield of the examined genotypes.