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1.
Article | IMSEAR | ID: sea-188627

ABSTRACT

Aims: Global warming and biological invasion are major environmental issues faced in the world. In the study, Rorippa amphibia, a perennial invasive clone plant in northern China, was used as a material to study the germination characteristics of the seeds at different temperatures. Study Design: Germination test of R. amphibia seeds at different temperature was studied by means of laboratory culture. The germination percentage, germination index, germination potential, bud height and root length of the seeds were determined. Place and Duration of Study: Samples were collected from the west side of the swimming pool of Shenyang Agricultural University of Liaoning Province in August 2017. Experiments were done in the College of Biological Science and Technology, between October 2017 and June 2018. Methodology: The petri dish method was used in the experiment. Fifty seeds were randomly selected and soaked in distilled water for 12h. The seeds were placed in a petri dish covered with double filter paper, cultured at 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ and 40℃ in light incubators for 12h darkness and 12h light (4000lux), with 3 repeats per processing. Seed germination was based on embryo root breakthrough seed coat ≥ 1 mm. During the experiment, the numbers of seed germination were recorded every day, and the filter paper was kept moist until there was no new seed germination for 2 consecutive days, which was regarded as the end of germination. The numbers of seed germination should be counted regularly every day, and the beginning and duration of germination should be recorded. The germination rate, daily germination rate, germinating potential, germinating index and vigor index of R. amphibia seeds at different temperature were calculated by measuring bud height and radicle length on the 10th day after germination. Results: The temperature range of seed germination of R. amphibia was wide, which could germinate at 15 - 40℃. Lower temperature delayed the peak period of seed germination at some extent and the germination rates of R. amphibia peak at 30 - 35℃, which were 44.67% and 50% respectively. At 35℃, germination potential and germination index were 25.33% and 29.46, reaching the maximum value. Conclusion: The reason for the wide temperature range of seed germination and the low germination rate might be the candidate method for clonal plant population establishment in temperate zone. The higher germination rate of high temperature condition suggested that clone invasive plants in temperate regions were more invasive during global warming.

2.
J Environ Biol ; 2013 Apr; 34(2suppl): 427-436
Article in English | IMSEAR | ID: sea-148547

ABSTRACT

This study aims to evaluate the impacts of low dissolved oxygen (DO) levels on activated sludge performance. Two sequencing batch reactors (SBR), each with a working volume of 10 l, were investigated with different DO levels. Compared with high DO conditions (above 2 mg l-1 on average), low DO conditions in the SBR did not result in poor sludge bulking, lower chemical oxygen demand, and ammonium removal efficiency. Moreover, simultaneous nitrification and denitrification (SND) via nitrite and shortcut nitrification-denitrification were carried out under low DO levels. The average efficiencies of SND and nitrite accumulation ratios (NAR) in reactors A and B were 10.6 and 60.4%, respectively, under high DO levels and 4.1 and 76%, respectively, under low DO levels. Scanning electron microscopy revealed that the main types of bacteria in reactor A were spherical and short rod-shaped bacteria, whereas those in reactor B were long rod-shaped bacteria and filamentous bacteria. Thus, the appropriate DO concentration created excellent microbial community structures, which helped the biological systems to perform well under low DO level operating conditions.

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