| Green roofs has received more and more attention for effectively improving urban ecological environment without occupying scarce urban land resources.Sedum sarmentosum Bunge performed a good application prospect in this field.But the lack of supporting establishment technique limited its extensive application.The experiments were conducted to study the effects of different temperatures,substrate water contents,nitrogen levels and light intensities on growth and physiological characteristics of S.sarmentosum (native species in Nanjing).In addition,its appropriate vegetative establishment method was also probed.This would help promote the utilization of S.sarmentosum in green roofs. The results were as follows:1.Temperature treatment of 35/30℃(day/night) significantly inhibited the shooting and growth,and reduced chlorophyll content of S.sarmentosum.Under 30/25℃and 25/20℃temperature treatments,S.sarmentosum showed better performance.Under 30/25℃,S.sarmentosum had more new shoots,leaves and larger shoot length,while 25/20℃was more conducive to the development of roots.There were no significant differences in terms of chlorophyll content,aboveground and total dry weight between the two treatments. Therefore,30～20℃was appropriate for the establishment of S.sarmentosum in green roofs. At same temperatures,the number of new shoots,shoot length and succulence extent of S. sarmentosum increased with the increase of substrate water content.Treatment of 50%WHC(water holding capacity) showed the highest chlorophyll content and non-dramatically reduced dry matter accumulation,which indicated that 50%WHC didn't cause obvious harm to S.sarmentosum.Moisture can be reduced under appropriate temperatures.30/25℃+70%WHC was the best temperature/moisture combination for establishment of S.sarmentosum.2.Nitrogen application increased total N,free amino acid,soluble protein, photosynthetic pigment and leaf water content,and promoted shooting and growth of S. sarmentosum,which would help accelerate establishment and improve ornamental quality. However,high level of nitrogen(10 g/m~2) might slightly inhibited early shooting,affected root development,dramatically decreased soluble sugar content and reduced dry matter accumulation.Therefore,nitrogen should be applied at a moderate level.5～7.5 g/m~2 was suggested under the experimental condition in this research.3.Within the light intensity range(23%～100%sunlight) in this experiment,S. sarmentosum could grow normally and showed good morphological plasticity.Low light intensity induced more new shoots and leaves,longer shoot and internode,smaller diameter and reduced specific leaf weight.Compared with 100%sunlight,shading promoted plant dry matter accumulation and more energy distribution to the growth of stem.All these changes help capture more light to adapt to low light environment.In addition,shading increased plant water content and soluble protein content,reduced soluble sugar content. Photosynthetic pigment content increased significantly only on 23%sunlight condition which caused dramatic negative influence to root development and slight decrease of plant dry weight contrasting to 47%sunlight.It suggested that moderate shading could improve the growth of S.sarmentosum,but light intensity lower than 23%sunlight should be avoided.4.Stem-cutting source,size and rate showed significant influence to the establishment of S.sarmentosum.The new shoots growth of distal stems was inhibited,but the stems performed fast growing which helped obtain the largest biomass and coverage.The upper-middle stems with leaves showed optimal new shoot quantity and maximum shoot length,and the biomass and coverage were not significantly different with distal stems.The lower-middle stems without leaves and the proximal stems performed poorly.New shoots quantity,maximum shoot length,biomass and coverage increased with the increase of node number.Stem-cuttings with 3 or 4 nodes were better than that with 2 nodes.Single plant growth was inhibited but establishment was speeded with the increase of stem-cutting rate. 300 g/m~2 performed better balance between the two aspects.Two establishment methods were not in significant differences. |
