effect of deficit irrigation on growth and yield of spring safflowers (carthamus tinctorius l.) genotypes in birjand

deficit of oil seeds and high volume of oil imports in iran, and limitation of water sources against production of many oil seed crops, demonstrate the importance of detection tolerant species and cultivars for stressful conditions and their most sensitive growth stages to saline stress. in order to study response of spring safflowers (carthamus tinctorius l.) genotypes to disruption irrigation in different reproductive growth stages and also to determine their most sensitive growth stage to stress induced by deficit irrigation, an experiment was conducted in a spilt plot arrangement based on randomized complete block design with four replications at research farm, faculty of agriculture, the university of birjand, iran during 2007-2008. irrigation regimes (full irrigation (whole season irrigation), irrigation until grain filling stage, irrigation until flowering, and irrigation until heading-bud) stages; and three cultivars (mahali isfahan, isfahan28 and il111) were arranged in main plots and subplots, respectively. the results showed that increasing distance between irrigations caused early maturation, reduce of growth duration, dry matter accumulation, leaf area index, crop growth rate and grain yield in all genotypes and detection in these parameters in mahali isfahan was the lost amount. overall, it seems that local genotype (mahali isfahan) had higher adaptability to deficit water in southern khorasan conditions due to its nativeness. finally, it was determined that heading-bud stage of safflower was very sensitive to water deficit, and water limitation at this stage, could considerably decrease growth duration, growth indices and grain yield. thus, watering at heading-bud stage is the most important parameter for improving safflower grain yield.