The relative magnitude of contribution of a photosynthetic source, to fulfill sink demands depends, at least in part, on the relative distance between the sources and sinks. For crop plants, in general, a major source for a reproductive sink is the closest one, i.e. inflorescence as well as the adjacent leaves. In order to evaluate the contribution of photosynthetates of inflorescence and the adjacent leaves to grain filling and yield in four safflower genotypes, planted in summer as a second crop, a 4-replicate RCBD field experiment was conducted in Isfahan in 2002. Treatments included three shading levels after pollination (control, head only, and head along with the two upper leaves), and four genotypes (Arak2811, Kouseh, Nebraska10 and AC-sterling). Based on phenological studies, Kouseh and AC-sterling were the latest and earliest in terms of maturity and the tallest and the shortest genotypes, respectively amongst genotypes studied in the experiment. While number of heads per plant was not significantly affected, number of seeds per head, 1000-seed weight and grain yield per plant were significantly decreased due to shade in the shading treatment. No significant difference was detected between the two shading levels, with respect to traits, except 1000-seed weight. With the environmental conditions encountered in this experiment and the method used, the contribution of photosynthetic surfaces of inflorescence, as well as the two adjacent leaves to safflower grain production was estimated to be relatively low, i.e. 12.4 to 14.2 percent. Among genotypes studied, Arak2811, Nebraska10 and Kouseh outperformed AC-sterling, thus the frist three genotypes could be recommended for planting in summer as a second crop in Isfahan.
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