By employing TCLs (thin cell layers) culture, the floral gradient in flowering tobacco of different developmental stages was confirmed. The TCLs from early flowering tobacco regenerated more floral buds than those fro...By employing TCLs (thin cell layers) culture, the floral gradient in flowering tobacco of different developmental stages was confirmed. The TCLs from early flowering tobacco regenerated more floral buds than those from the tobacco plants in full blooming or fruiting stages. Analysis of free amino acid levels revealed the acropetal gradient of Pro in flowering tobacco stem. L-Pro. L-Trp. D,L-Met and L-Arg were respectively added into the culture medium for testing their influence on floral bud formation from tobacco pedicel segments. Only L-Trp evidently enhanced the floral bud neoformation.展开更多
To study the relationship between zooplankton community structure and environmental factors and water quality in the Harbin Section of the Songhua River,investigations were carried out in June,August,and October 2011....To study the relationship between zooplankton community structure and environmental factors and water quality in the Harbin Section of the Songhua River,investigations were carried out in June,August,and October 2011.Canonical correspondence analysis(CCA) and saprobic indices were used to process and analyze the data.Seasonal variability was identified as a significant source of variation,which explains the fluctuation in zooplankton density.In autumn,the dry season,water residence time increased and zooplankton biomass and abundance accumulated in the slow flowing waters.Zooplankton abundance increased when food conditions improved.Therefore,the total zooplankton abundance in autumn is much higher than that in spring and summer.According to the saprobic indices,all the sample sites had mesosaprobic water and water quality was worse in autumn.CCA revealed that temperature accounted for most of the spatial variation in the zooplankton community.Moreover,pH,dissolved oxygen saturation,and turbidity were important factors affecting zooplankton community distribution.展开更多
Despite the rapid development of flower-viewing tourism in China in recent years,there is almost no systematic research on it.Therefore,this study analyzes the spatial and temporal distribution characteristics of flow...Despite the rapid development of flower-viewing tourism in China in recent years,there is almost no systematic research on it.Therefore,this study analyzes the spatial and temporal distribution characteristics of flower-viewing tourism and its influencing factors in China using the spatial statistical analysis methods and the geographic detector method.The study uses the Point-of-Interest data of flower-viewing tourist attractions from networks such as Qunar and Ctrip,the flower observation data from China Phenological Observation Network,Chinese network news,and Weibo,and the statistical data from yearbooks.The results are as follows:1)The spatial attribution type of flower-viewing tourism in China is aggregated into areas,including two high-density aggregated areas,three medium-density aggregated areas,and one general-density aggregated area.Furthermore,five major types of flower-viewing tourist attractions have formed several aggregated areas.2)The time of flower viewing in China starts from about February and lasts about eight months till October each year.Florescence and flowering time of different ornamental flowers in different regions are different.3)The spatial and temporal distribution characteristics of flower-viewing tourism in China are mainly affected by ornamental flower phenology,spatial distribution characteristics of flower-viewing resources,regional permanent population size,youth population size,female population size,regional GDP,and added value of the tertiary sector.These conclusions clarify the spatial and temporal distribution characteristics of flower-viewing tourism and its influencing factors in China.They could provide a scientific basis and useful reference for the coordination and sustainable development of regional flower-viewing tourism in China.展开更多
文摘By employing TCLs (thin cell layers) culture, the floral gradient in flowering tobacco of different developmental stages was confirmed. The TCLs from early flowering tobacco regenerated more floral buds than those from the tobacco plants in full blooming or fruiting stages. Analysis of free amino acid levels revealed the acropetal gradient of Pro in flowering tobacco stem. L-Pro. L-Trp. D,L-Met and L-Arg were respectively added into the culture medium for testing their influence on floral bud formation from tobacco pedicel segments. Only L-Trp evidently enhanced the floral bud neoformation.
基金Supported by the National Natural Science Foundation of China(No.41271106)
文摘To study the relationship between zooplankton community structure and environmental factors and water quality in the Harbin Section of the Songhua River,investigations were carried out in June,August,and October 2011.Canonical correspondence analysis(CCA) and saprobic indices were used to process and analyze the data.Seasonal variability was identified as a significant source of variation,which explains the fluctuation in zooplankton density.In autumn,the dry season,water residence time increased and zooplankton biomass and abundance accumulated in the slow flowing waters.Zooplankton abundance increased when food conditions improved.Therefore,the total zooplankton abundance in autumn is much higher than that in spring and summer.According to the saprobic indices,all the sample sites had mesosaprobic water and water quality was worse in autumn.CCA revealed that temperature accounted for most of the spatial variation in the zooplankton community.Moreover,pH,dissolved oxygen saturation,and turbidity were important factors affecting zooplankton community distribution.
基金The National Key Research and Development Program of China(2019YFB1405600)The General Project of Scientific Research Program of Beijing Municipal Education Commission(SM202110031002)+1 种基金The Humanities and Social Sciences Foundation of the Ministry of Education in China(18YJA630102)The Youth Academic Talents Project of Beijing International Studies University(21110010005).
文摘Despite the rapid development of flower-viewing tourism in China in recent years,there is almost no systematic research on it.Therefore,this study analyzes the spatial and temporal distribution characteristics of flower-viewing tourism and its influencing factors in China using the spatial statistical analysis methods and the geographic detector method.The study uses the Point-of-Interest data of flower-viewing tourist attractions from networks such as Qunar and Ctrip,the flower observation data from China Phenological Observation Network,Chinese network news,and Weibo,and the statistical data from yearbooks.The results are as follows:1)The spatial attribution type of flower-viewing tourism in China is aggregated into areas,including two high-density aggregated areas,three medium-density aggregated areas,and one general-density aggregated area.Furthermore,five major types of flower-viewing tourist attractions have formed several aggregated areas.2)The time of flower viewing in China starts from about February and lasts about eight months till October each year.Florescence and flowering time of different ornamental flowers in different regions are different.3)The spatial and temporal distribution characteristics of flower-viewing tourism in China are mainly affected by ornamental flower phenology,spatial distribution characteristics of flower-viewing resources,regional permanent population size,youth population size,female population size,regional GDP,and added value of the tertiary sector.These conclusions clarify the spatial and temporal distribution characteristics of flower-viewing tourism and its influencing factors in China.They could provide a scientific basis and useful reference for the coordination and sustainable development of regional flower-viewing tourism in China.
