Due to the importance of quantitative traits, much research has been done regarding their heritability. Such research in breeding quantitative characteristics is so essential that methods and advanced theories about the trend of heritability have been developed rapidly. The present paper is the result of the research which has been conducted towards achieving two aims. In the first section variation in yield components of sunflower in different growth patterns was found out. Three hybrids were chosen to grow in a split plot design in Karaj Central Agricultural Research Organization fields during 1994. Materials consisting of "the three hybrids, were CMS 14xR-28, CMS 24xR-43 and Mehr. Some of the scored characters for 10 chosen plants were: plant height, stem diameter, head diameter, leaf area, sedd oil content and 100 seed weight. The results showed that changes in plant density affect all the characters, such effect being more pronounced in head diameter, yield per head and oil yield per heactare. Hybrid (CMS 14xR-28) yilded the maximum seed per hectare. The second phase fllowed the analysis of multiple regression
in some traits of sunflower in different hybrids and different plant densities. The aim was to find those characters which affect yield more than the others in different growth patterns. These characters were plant height, head diameter, stem diameter and leaf area, which showed varied contributions to
seed yield. As a whole, the head diameter presented the highest significant association with seed yield.
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