Defoliation Effects on Sunflower (Helianthus annuus L.) Seed Yield and Oil Quality

The objective of the present study was to determine the influence of artificial defoliation on sunflower seed yield, oilcontent, and fatty acid composition. The research was carried out at S.leyman Demirel University, Isparta, Turkey, during 2002 and2003. Six defoliation levels [0 (control), 5, 10, 15, 20 and 25 leaves per plant] were applied at the preflowering stage from bottomto top leaves. The results demonstrate a close relationship between yield reduction and the defoliation levels. The higher the defoliation level, the higher the yield reduction. Complete and partial leaf removal treatments reduced oil percentage of seed when compared with the undefoliated check. However, oleic acid and linoleic acid levels in seed were not significantly affected bydefoliation treatments.