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Simple, accurate, and non-destructive methods for determining leaf area (LA) of plants are important for many experimental comparisons. Determining the individual LA of sunflower (Helianthus annuus L.) involves measurements of leaf parameters such as length (L) and width (W), or some combinations of these parameters. Two field experiments were carried out during 2003 and 2004 to compare predictive equations of sunflower LAs using simple linear measurements. Regression analyses of LA vs. L and W revealed several equations that could be used for estimating the area of individual sunflower leaves. A linear equation having W 2 as the independent variable provided the most accurate estimate (r 2 = 0.98, MSE = 985) of sunflower LA. Validation of the equation having W 2 of leaves measured in the 2004 experiment showed that the correlation between calculated and measured areas was very high.Additional key words: Helianthus annuus L.; leaf parameters; non-destructive methods.--Leaf area (LA) is associated with many agronomic and physiological processes including growth, photosynthesis, transpiration, photon interception, and energy balance (Goudriaan and Van Laar 1994). The equation which can predict LA without causing harm to the plant can provide researchers with many advantages in physiological experiments. Moreover, the equations enable researchers to measure LA on the same plants during the plant growth period and may reduce variability in experiments (Serdar and Demirsoy 2006).Despite various techniques used to estimate leaf area (Lu et al. 2004), the most common approach is to develop ratios and regression estimators by using easily measured leaf parameters such as length (L) and width (W; Kvĕt and Marshall 1971). This method usually saves time and is non-destructive. Various combinations of measurements and various equations relating leaf L and W to leaf area have been used in, for example, tomato (Schwarz and We needed a good equation for non-destructive LA estimation for use in physiological and agronomical studies on the vegetative growth phase of sunflower. Therefore, the aims of this study were (1) to compare existing predictive LA equations for sunflower leaves using non-destructive measurements; and (2) to assess the accuracy of the optimum equation selected using an independent dataset. Sunflower (Helianthus annuus L., cv. Melody) leaves used for all measurements and estimations were from two field experiments conducted during 2003 (May-September) and 2004 (May-October) at Tal Amara Research Station in the Bekaa Valley of Lebanon (33°51'44''N, 35°59'32''E, 905 m a.s.l.). The plants were grown in a completely randomized block design with 4 replications. The size of each plot was 3×10 m. Row spacing (four rows) was 0.80 m and the distance between plants in the row was 0.20 m providing a sowing density of 6 plants per m 2 . In both experiments, fertilizer was applied before seeding at a rate of 300 kg ha -1 of NPK (15-15-15). Additionally, 150 kg ha -1 of ammonium nitrate (34N) and 50 kg ha -1 of potassium n...

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