Effects of pretreatment on germination of Typha domingensis and Phragmites australis

Global changes and human activities have negative effects on the wetland habitats,which decrease the area of wetland,reduce species diversity,and hinder the ecological functions. Wetland restoration,especially dominant plants restoration is critical and urgent to improve wetland conditions and areas worldwide. As the largest tributary of the Heilong River,Songhua River drains nearly 70% of the Northeast China's land area. The riparian wetland along the downstream of Songhua River is suffering from ecological degradation of native vegetation. Typha domingensis(T. domingensis) and Phragmites australis(P. australis) are two dominant species in this basin,and play an important role in sustaining regional environmental functions. Seeds are produced annually,which would allow ample opportunities for colonization by sexual propagation. Seed propagation is considered to be an effective and feasible technique for vegetation restoration. In order to explore the optimal seed-soaking reagents to accelerate seed germination of T. domingensis and P. australis,the pure live seeds of both species were collected from a riparian wetland along the downstream of Songhua River(47°16'39.4.″ N,132°02'44. 2″ E),and the seeds germination experiment was conducted in incubator(LRH-250-GS II,China) with an alternating diurnal regime of 12 h of daylight at 25 ℃ and 12 h of darkness at 15 ℃ in laboratory. Effects of 8 different pretreatments(untreated,soaking with distilled water,soaking with 0.1% H2O2,soaking with 0.1% H2O2and then rinsing with distilled water,soaking with 0.1% KNO3,soaking with 0.1% KNO3and then rinsing with distilled water,soaking with0.1% KMnO4,soaking with 0.1% KMnO4and then rinsing with distilled water,respectively) on germination percentage(GP) and germination speed(GS) of T. domingensis and P. australis seeds are observed for 10 days. For each treatment,100 seeds(four replicates) were placed on a layer of Whatman grade No.1 filter paper(pH 7) in 90 mm Petri dishes with distilled water to keep moist during the whole experiment. Results showed as follows:(1) Differences between untreated seeds and pretreated ones with reagent soaking on GP and GS of T. domingensis and P. australis were significant;(2) GP and GS of T. domingensis under the pretreatment of soaking with 0.1% KMnO4and then rinsing with distilled water were significantly greater than that of the rest pretreatments,and the average GP of T. domingensis was about 3.1 times greater than the untreated and the GS was up to 16. 17 ± 0. 80;(3) Seed germination of P. australis performed best under the treatment of soaking with 0.1% concentration KNO3and rinsing with distilled water,and its GP and GS were up to 96%—99% and 28.43±0.71,respectively. The results indicate that seed pretreatment(seed-soaking reagent) is one of the most indispensable and efficient methods of accelerating the seed germination and seedling growth of T. domingensis and P.australis. Rapid and effective restoration of the two dominant plants in the riverine wetlands along the downstream of Songhua River,therefore,could be expected through collecting their pure live seeds and pretreating the seeds with 0.1%KMnO4and 0.1% KNO3and then rinsing with distilled water respectively before dispersal.