Germination Ecology of Invasive Sticky Nightshade ( <i>Solanum sisymbriifolium</i> )

Abstract Sticky nightshade ( Solanum sisymbriifolium Lam.) has emerged as a significant invasive weed across agricultural and natural ecosystems globally. The species contains toxic steroidal glycoalkaloids that pose a risk to livestock. Furthermore, its ability to form dense infestations can reduce the abundance of desirable plant species and hinder management of both natural and agricultural systems. Despite its increasing impact, information on its germination ecology and seedling emergence behaviour remains limited. A series of laboratory and glasshouse experiments were conducted to investigate the effects of temperature, light, pH, salinity, moisture stress, and burial depth on the seed germination and seedling emergence of S. sisymbriifolium . Results showed that germination was highest (85.5%) under diurnally alternating temperatures of 35/15 C, while light had no significant effect. Seed germination was 74.1-84.7% across a wide pH range (4 - 10), indicating minimal sensitivity to pH variation. Germination declined sharply with increasing salinity and was completely inhibited at 125 mM NaCl. Similarly, germination decreased from 85.1% to zero as osmotic potential declined from 0 to −0.80 MPa, indicating that S. sisymbriifolium requires sufficient moisture for successful germination. Seedling emergence was greatest (72.4%) at a burial depth of 2.5 cm and declined significantly at greater depth. Overall, this study demonstrates that S. sisymbriifolium can grow in a broad range of environmental conditions but is sensitive to moisture stress, salinity, and deeper burial. This ecological flexibility may facilitate its spread across diverse habitats. These findings provide useful guidance for designing more efficient and sustainable integrated weed management strategies to reduce germination and seedling emergence of this invasive species.