This experiment was carried out in Golestan province, in a randomized complete block design (RCBD) with four replicates. Wheat genotypes were included N-91-9, N-91-17, Tiregan, Nogal, Euclide, Agorazado, Lucullus, and Antonius. Sampling from Flag leaf and other leaves at 10 stages included 7DBA (Day before anthesis), 3DBA, Anthesis, 3DAA (Day after anthesis), 7DAA, 11DAA, 15DAA, 19DAA, 23DAA, and 27DAA was done and carried to laboratory in liquid nitrogen and stored at -80 °C. Part of the leaf samples was carried with a paper pocket and incubated in the oven at 80 °C for 48 hours. Biochemical traits such as chlorophyll content, net photosynthetic rate, sucrose content, sucrose synthase (SS) and sucrose phosphate synthase (SPS) content, grain yield, and photosynthetic genes expression included RbcL, RbcS, and Rca was measured in all stages. The result had shown that flag leaf in the post-anthesis stages has a significant role in photosynthesis and sucrose production in the plant and cultivars with higher chlorophyll content also had higher photosynthesis. Also, in genotypes with higher SS enzyme activity, more sucrose is synthesized and due to the role of SPS, increasing its amount is involved in the transfer of sucrose from the leaves to other organs. The RbcL, RbcS, and Rca genes had higher expression in cultivars with higher photosynthesis than the control (Tiregan). Among the studied genotypes, the results showed that Nogal cultivar and line N-91-17 had superior in terms of grain yield and other measured traits and can be recommended for use in future research. Manuscript profile