Allelopathic effect of different plant extracts on the Germination of Sunflower (Helianthus Annuus) seeds

This study investigated the allelopathic effects of different plant extracts on the germination and growth of sunflower (Helianthus annuus) seeds. The experiment was conducted in 2022 at the Institute of Biological Sciences, Gomal University Dera Ismail Khan, Pakistan. Sunflower seeds were treated with leaf extracts of Moringa oleifera, Psidium guajava, and Ziziphus mauritiana, with a control group receiving tap water. Both laboratory and field experiments were performed to assess germination, morphological, and physiological parameters such as Germination Index (GI), Germination Percentage (GP%), Seed Vigor Index (SVI), Shoot Length (cm), Root Length (cm), Fresh Shoot weight (gm), Dry Shoot Weight (gm), Fresh Root Weight (gm), Dry Root Weight (gm), Chlorophyll Content of Leaf and Carotenoid content of leaf. Among the treatments, Ziziphus mauritiana leaf extract exhibited the highest germination percentage (73.33%) and germination index (1.93). The seed vigor index was highest in Ziziphus mauritiana (319.7) and Psidium guajava treatments but lowest in Moringa oleifera (88.2) compared to the control. Morphological parameters such as shoot length, fresh and dry shoot weight, fresh and dry root weight were negatively affected by all extracts, whereas root length was enhanced by Ziziphus mauritiana (10.6cm) but reduced by the other extracts. Physiological parameters, including chlorophyll (a, b, and total chlorophyll content) and carotenoid content, were also adversely affected by all treatments. These findings suggest that while Ziziphus mauritiana leaf extract promotes seed germination and root elongation, most plant extracts exhibited inhibitory effects on sunflower seedling growth and physiological traits.