response of spring safflower genotypes under shading of head and nearest leaves in birjand conditions

in order to study the effects of shading on head and its near leaves on yield and yield components of spring safflower genotypes, an experiment was conducted in factorial arrangement based on a complete randomized block design with four replications at agricultural research station, faculty of agriculture, birjand university during 2008. factors were including three spring safflower genotypes (koose (a local variety), isfahan28 and il111) and three shading levels after anthesis (on head, head+ two nearest leaves and non-shading (control)). the results showed that there was significant differences between shading treatments regarding number of fertile heads per plant, number of seeds per head, 1000-kernel weight, kernel yield and harvest index, whereas number of heads per plant and biological yield were not affected by shading. also between two shading levels was not significantly different. there was a significant difference between cultivars in respect to all measured traits. the highest and lowest kernel yield obtained in koose and il111, respectively and there was not significant difference between koose and isfahan28 in respect to all measured traits. shading on head and near leaves reduced kernel yield by 20.54%. therefore, it can be concluded that photosynthesis of inflorescence and nearest leaves plays important role in seed production of safflower as same as small seed cereal.