Effects of Environmental Factors on Seed Germination and Seedling Emergence of Solanum nigrum LOA

Solanum nigrum L is a widespread annual weed infesting in peanut fields in China,and it causes severe damage to peanut production in Xinjiang.In this study,the seed germination biological characteristics of S.nigrum populations collected from Kashgar,Xinjiang(KS)and Qingdao,Shandong(QD)were determined under laboratory conditions.The results showed that the optimal germination temperature for both populations was 25-30℃,within which the time required for 50%germination(t_(50))was the shortest as only 2.02 d.Compared with constant temperature,fluctuating temperature slightly decreased the seed germination rate.Seed germination was sensitive to light and photoperiod,with germination rates of 96.5%-97.5%,76.0%-78.0%,and 54.0%-58.0%under 12 h light/12 h dark,full light,and full dark conditions,respectively.Both populations maintained germination rates above 86.5%under pH 4-10.NaCl stress and osmotic stress significantly inhibited seed germination,and 280 mmol/L NaCl and-0.9 MPa osmotic stress completely inhibited germination,respectively The highest seedling emergence rate(91.0%-93.5%)was observed at a burial depth of 1.0 cm,and the emergence rate still exceeded 81.5%at burial depths ranging from O.5 to 2.O cm.Comparison between the two populations revealed that the KS population had a significantly higher germination rate than the QD population under several temperature regimes,especially under suboptimal temperatures(constant temperatures of 15,20,and 35℃;alternating temperature of 20/10℃).The KS population also exhibited significantly higher germination rate than the QD population under 20-240 mmol/L NaCl or-0.7 to-0.3 MPa osmotic stress.The KS population showed strong germination resistance to low temperature,drought,and high-salt stresses,which may be one of the critical reasons for its dominance as a weed population in peanut field in Xinjiang.