Abstract Khasi nightshade ( Solanum khasianum C.B. Clarke) is a perennial poisonous weed in tropical and subtropical regions that seriously threatens the development of grasslands. For a high-risk invasive weed, a comprehensive understanding of its seed germination characteristics is important for predicting its spread and developing effective management strategies. However, the impact of various abiotic factors on the germination of S. khasianum is not clear. The study first explored the effect of temperature, light, pH, osmotic stress, salt stress, high-temperature pretreatment and burial depth on the germination of S. khasianum . Seeds germinated at constant temperature of 30, 33, 35, and 38 C, and the germination rate (GR) ranged from 10% to 94%. The optimum germination temperature was 35 C, while germination was completely inhibited at 25 C or 40 C. The germination of S. khasianum was greatly promoted by alternating light and darkness (16/8, 12/12, 8/16 h), but was not sensitive to the time change of photoperiod. The GRs were more than 70% in the pH range of 4 to 10, and strongly acidic environment was more suitable for the germination. The GR gradually decreased with the osmotic potential from 0 to -0.2 MPa, and no germination occurred at -0.4 MPa. Accordingly, germination was also low in sodium chloride (NaCl) solution with concentration higher than 60 mM. Seeds of S. khasianum were not tolerant to high temperature, GR decreased significantly after exposure to 40 C for five minutes, and it decreased to 3% at 120 C. The emergence rate was the highest (93%) when the seeds were buried on the soil surface, while seedlings hardly appeared when the burial depth was more than 2 cm. This study revealed the possible adaptive mechanism of invasive S. khasianum , and will contribute to the effective prediction and management in grasslands.
Xu et al. (Fri,) studied this question.