Dose-dependent Influence of Chiraito (Swertia spp.) Seed Coating on Sunflower Germination and Seedling Vigor

Abstract

Sunflower (Helianthus annuus L.) is an important oilseed crop whose successful establishment depends largely on rapid and uniform seed germination and seedling vigor. In recent years, plant-derived biostimulants have gained considerable attention as eco-friendly alternatives for enhancing early crop growth and development. This study evaluated the dose-dependent allelopathic and biostimulatory effects of chiraito (Swertia spp.) seed coating on sunflower germination, seedling growth, and vigor characteristics under controlled laboratory conditions. The experiment was conducted in a Completely Randomized Design (CRD) with seven concentrations of chiraito aqueous extract of 0, 2, 4, 6, 8, 10, and 12%. Germination was assessed using the standard paper towel method in a germinator, and parameters, including germination percentage, mean germination time, root length, shoot length, and seedling vigor indices, were recorded. The results revealed significant dose-dependent responses to chiraito extract application. Moderate concentrations of 4% and 6% significantly enhanced germination percentage, reduced mean germination time, and improved root and shoot growth, resulting in higher seedling vigor indices. The best overall performance was observed at 6% concentration. In contrast, higher concentrations (8–12%) inhibited germination and seedling growth, indicating possible allelopathic toxicity at elevated doses. The findings suggest that chiraito extract may serve as a potential natural biostimulant for improving early sunflower establishment when applied at optimal concentrations.