Essential oils on germination, physiological quality, and enzymatic activity of bean seeds

Abstract

The objective of this study was to evaluate the effects of essential oils from Thymus vulgaris (thyme) and Cymbopogon citratus (cymb oil) on the germination, physiological quality and enzymatic activities of common bean seeds. The oils were tested at different concentrations (0, 1, 3, and 5 mL kg^-¹), and effects were assessed through germination, and seedling emergence tests. In addition, the levels of chlorophylls, carotenoids, phenolic compounds, and activities of esterase and acid phosphatase enzymes were evaluated. Cymb oil inhibited germination at higher concentrations, with a germination rate of 66% at 5 mL kg^-¹, whereas thyme oil, at the highest dose, reduced root dry mass (0.12 g per seedling). At lower concentrations, thyme oil promoted higher chlorophyll contents than cymb oil. Furthermore, enzymatic analysis indicated an increase in acid phosphatase and esterase activities in seeds treated with cymb oil, suggesting distinct physiological responses. Overall, thyme oil at 1 mL kg^-¹ improved seedling growth and pigment contents, while higher doses impaired seed performance. In contrast, cymb oil at 1–3 mL kg^-¹ enhanced shoot length, root dry mass, and enzymatic activities, but inhibited germination at 5 mL kg^-¹.