Solanum nigrum seed viability and germination, and soil modulation effect on seedling emergence

Abstract

Solanum nigrum is an important African medicinal plant with culinary and health benefits. However, scavenging from the wild has been the means of its accessibility, and this comes with several challenges. Cultivation of this plant is thus critical if populations in the wild are to be maintained and if it can be accessed throughout the year. Environmental factors such as growth media are important in plant production and growth. Therefore, identifying the best soil texture type and ideal sowing depth for optimum seedling emergence of S. nigrum was investigated in this study. Seeds extracted from plants growing in the wild in Alice, Eastern Cape Province of South Africa were tested for viability, germination, and seedling emergence on different soil types. The experiment was set up in a randomised complete block design in the glass house, University of Fort Hare, Alice, South Africa. Treatments were light, temperature, and scarification. Sandpaper scarification and 15°C, 20°C, and 25°C temperature treatments all produced the highest germination percentage of 94.66%. Although continuous light produced 75.33%, alternating light and continuous darkness produced 84% and 4.66%, respectively. Continuous darkness, 5°C, 35°C, and 40°C temperature regimes produced less than 5% germination percentage. The efficacies of sandy clay loam, silty clay loam, clay loam, and loam soils were tested on seedling emergence. Sowing depths lower and higher than 2 cm significantly slowed down seedling emergence. Control soil also reduced seedling emergence. The results indicate that S. nigrum seeds germinate better at temperatures between 15°C and 25°C and scarification with sandpaper, continuous darkness, and temperatures lower than 5°C. However, temperatures higher than 35°C hinder germination. The highest seedling emergence was recorded at 2 cm, planting depth in silty clay loam soils. These results can be applied not only to S. nigrum seeds but also to other research fields that rely on successful seed germination.