Study of the Relationships Between Sunflower Growth Traits and Heavy Metal Uptake Under Field Pollution Conditions

This study aimed to quantitatively evaluate the relationship between two physiological growth traits (stem height and leaf area) and the uptake of three heavy metals (chromium, cobalt, and nickel) from contaminated soils by sunflower (Helianthus annuus L.). A pot experiment was conducted using three sunflower cultivars (local, American, and Spanish) grown in soils collected from three locations in northwestern Syria (Harem, Sarmada, and Darat Izza) for 45 days. The experiment was arranged in a Randomized Complete Block Design (RCBD) with three replicates. Data were analyzed using Two-Way Analysis of Variance (Two-Way ANOVA), Pearson's correlation coefficient (r), and simple linear regression.

The results revealed that leaf area was significantly and positively correlated with the uptake of all three heavy metals, with correlation coefficients of (r = ***0.783) for chromium, (r = ***0.691) for cobalt, and (r = ***0.825) for nickel (p < 0.001). Regression models based on leaf area explained between 47.8% and 68.0% of the variation in metal uptake (R² = 0.478–0.680). In contrast, stem height showed significant positive correlations only with chromium (r = **0.615, p < 0.01) and nickel (r = *0.470, p < 0.05), whereas no significant relationship was observed with cobalt. Although Harem soil contained the lowest total concentrations of the studied metals, it exhibited the highest uptake levels, indicating that metal bioavailability, rather than total soil metal concentration, is the principal determinant of metal uptake.

These findings demonstrate the potential for developing preliminary predictive models that can be further refined and validated in future studies. Moreover, they highlight leaf area as a reliable proxy indicator for estimating phytoremediation efficiency prior to laboratory-based metal analysis.