عنوان مقاله [English]
To evaluation of effects of plant density and defoliation in two development stages on yield and yield components of sunflower, two year research was carried out during 2004-2006 in the agriculture research station of Khoy. The experiment was done in split factorial in the basis of randomized complete block design in three replications. The plant density levels were considered as the main factor in three levels of 30000, 40000, 50000 plants per hectare and defoliation percentage in four levels (0, 33, 66 and 100 percent) and defoliation stage in appearance of anthodium and anthesis were as the sub factors. The results of compound analysis of variance showed that plant density effect was significant on plant height and stem diameter, seed numbers in an anthodium, thousand seed weight, plant lodging percentage and grain yield. The maximum grain yield was obtained in 50000 plant density per hectare treatment with optimum leaf area index and sufficient number of anthodium in area unit. However, this treatment caused the least number of seeds in an anthodium and thousand seed weight. Increasing defoliation percentage resulted in decreased number of seeds in an anthodium, thousand seed weight, grain yield and harvest index. Defoliation in the anthesis stage had more negative effect on thousand seed weight, number of seeds in an anthodium, grain yield and harvest index than defoliation in appearance of anthodium. The results showed that cropping of sunflower in density of 50000 plants per hectare with leaves protection and high leaf area duration resulted in economical yield in Khoy region and so, even little percentage of defoliation in any different development stages wasn’t recommended.