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211.
This research aimed to investigate the interspecific and intraspecific identification of Dendrobium by using the multi-locus method so as to provide a molecular basis for Dendrobium identification through the combination of chloroplast psbA-trnH intergenic region sequences and ribosome 5S rRNA gene spacer sequences. PCR direct sequencing was applied to detect the chloroplast psbA-trnH intergenic region sequences as well as the ribosome 5S rRNA gene spacer sequences of 12 Dendrobium species, while the psbA-trnH intergenic region sequences of Dendrobium denneanum dq-2 variety and dq- 5line were cloned and sequenced for single nucleotide polymorphism (SNP) analyzing. The sequences were analyzed by the software Sequencher4.14, Bioedit7.0, MEGA5.2 and Dansp5.0; the interspecific and intraspecific Kimara-2-Parameter(K2P) distances were also calculated. The phylogenetic tree (using Neighbor joining method) was constructed with Bulbophyllum odoratissimum and Bletilla striata as outgroup. The results showed an average length of chloroplast psbA-trnH gene sequences in Dendrobium as 742.3 bp, with 72 variable sites, including 33 information sites; the average length of the ribosome 5S rRNA gene spacer sequences in Dendrobium was 336.4 bp, with 213 variable sites including 139 information sites. Using psbAtrnH intergenic region sequences in combination with ribosome 5S rRNA gene spacer sequences can not only identify D. denneanum, D. hancockil, D. thysiflorum, D. devonianum, D. moniliforme, D. chrysotoxum, D. officinale, D. heterocarpum and D. nobile, but also differentiate D. officinale from different geographical populations, and distinguish the dq-2 variety and dq 5line with SNP in the multi locus of D. denneanum. 相似文献
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213.
Ozone concentrations, flux and potential effect on yield during wheat growth in the Northwest-Shandong Plain of China 总被引:1,自引:0,他引:1
Ozone (O3) concentration and flux (Fo) were measured using the eddy covariance technique over a wheat field in the Northwest-Shandong Plain of China. The O3-induced wheat yield loss was estimated by utilizing O3 exposure-response models. The results showed that: (1) During the growing season (7 March to 7 June, 2012), the minimum (16.1 ppbV) and maximum (53.3 ppbV) mean O3 concentrations occurred at approximately 6:30 and 16:00, respectively. The mean and maximum of all measured O3 concentrations were 31.3 and 128.4 ppbV, respectively. The variation of O3 concentration was mainly affected by solar radiation and temperature. (2) The mean diurnal variation of deposition velocity (Vd) can be divided into four phases, and the maximum occurred at noon (12:00). Averaged Vd during daytime (6:00–18:00) and nighttime (18:00–6:00) were 0.42 and 0.14 cm/sec, respectively. The maximum of measured Vd was about 1.5 cm/sec. The magnitude of Vd was influenced by the wheat growing stage, and its variation was significantly correlated with both global radiation and friction velocity. (3) The maximum mean Fo appeared at 14:00, and the maximum measured Fo was − 33.5 nmol/(m2·sec). Averaged Fo during daytime and nighttime were − 6.9 and − 1.5 nmol/(m2·sec), respectively. (4) Using O3 exposure-response functions obtained from the USA, Europe, and China, the O3-induced wheat yield reduction in the district was estimated as 12.9% on average (5.5%–23.3%). Large uncertainties were related to the statistical methods and environmental conditions involved in deriving the exposure-response functions. 相似文献
214.
Ozone (O3) is an important atmospheric oxidant. Black carbon (BC) particles released into the atmosphere undergo an aging process via O3 oxidation. O3-aged BC particles may change their uptake ability toward trace reducing gases such as SO2 in the atmosphere, leading to different environmental and health effects. In this paper, the heterogeneous reaction process between O3-aged BC and SO2 was explored via in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Combined with ion chromatography (IC), DRIFTS was used to qualitatively and quantitatively analyze the sulfate product. The results showed that O3-aged BC had stronger SO2 oxidation ability than fresh BC, and the reactive species/sites generated on the surface had an important role in the oxidation of SO2. Relative humidity or 254 nm UV (ultraviolet) light illumination enhanced the oxidation uptake of SO2 on O3-aged BC. The oxidation potentials of the BC particles were detected via dithiothreitol (DTT) assay. The DTT activity over BC was decreased in the process of SO2 reduction, with the consumption of oxidative active sites. 相似文献
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Geosmin is a secondary metabolite responsible for earthy odors. The occurrence of geosmin has great impact on the quality of water environment. The gene essential for geosmin biosynthesis have been identified in several species. But little is known about the mechanism of geosmin synthesis in Aphanizomenon gracile. This study attempted to clone the gene involved in geosmin biosynthesis of Aphanizomenon gracile a nd a nalyze t he geosmin production u nder d ifferent e nvironments. T he high-efficiency thermal asymmetric interlaced PCR (hiTAIL-PCR) was used to amplify the full-length of geosmin synthase gene from Aphanizomenon gracile (WH-1). Real time PCR (RT-PCR) was applied to quantify the geosmin production in different light and temperature. As a result, geo, a geosmin synthase gene from Aphanizomenon gracile (WH-1) was cloned by hiTAIL-PCR. The full-length open reading frame (ORF) of geo was 2 262 bp, coding for a protein of 753 amino acids. Meanwhile, WH-1 was treated with different environment conditions and mRNA expression levels of geo were quantified by RT-PCR. It was found that low temperature (15 °C), high light intensity (35 μmol m-2 s-1) and continuous light illumination were beneficial to the expression of geo. The successful amplification of geosmin synthase gene verified that hiTAIL-PCR is an effective and simple procedure of low cost. The result provides fundamental knowledge on the monitoring and prevention for odorants. 相似文献
218.
Fine sediments in shallow water bodies such as Lake Okeechobee are prone to resuspension. Predominantly inorganic "mud" sediment that covers approximately 670 km2 of the lake has been recognized as a persistent source of turbidity. The objective of this study was to determine if mineral components of sediments in Lake Okeechobee and water conveyances of the northern Everglades also occur as suspended sediment and hence constitute a potential abiotic contributor to turbidity. Sediment samples were collected from nine stations within the lake and eight locations north of Water Conservation Area 2A in the Everglades. Water samples were also collected at selected locations. The silt and clay mineralogy of sediment and suspended particles was determined using X-ray diffraction, thermogravimetry, scanning-electron microscopy, energy-dispersive X-ray elemental microanalysis, and high-resolution transmission-electron microscopy. Clay fractions of the lake sediment contained the Mg silicate minerals sepiolite and palygorskite, along with smectite, dolomite, calcite, and kaolinite. Sediment silt fractions were dominated by carbonates and/or quartz, with smaller amounts of Ca phosphates and sepiolite. Mineralogy of the mud sediment was similar to that reported for geologic phosphate deposits. This suggests that the mud sediment might have accumulated by stream transport of minerals from these deposits. Suspended solids and mud-sediment mineralogy were similar, except that smectite was more abundant in suspended solids. Everglade samples also contained Mg-rich minerals. The small size, low density, and fibrous or platy nature of the prevalent mud sediment minerals make them an abiotic, hydrodynamically sensitive source of persistent turbidity in a shallow lake. Mitigation efforts focused exclusively on P-induced biogeochemical processes do not address the origin or effects of these minerals. Ecological management issues such as turbidity control, P retention, geologic P input, and suitability of dredging are related to mud-sediment properties and provenance. 相似文献
219.
Response to environmental flows in the lower Tarim River, Xinjiang, China: ground water 总被引:1,自引:0,他引:1
In China's west since the 1950s large-scale ecosystem degeneration has occurred through water diversions for agricultural purposes. Since 2000, 1038 x 10(6) m(3) of water have been released into the Tarim River with the result that water reached the terminal Taitema Lake for the first time in 30 years. This environmental flow raised water-table levels along 350 km of the river. To assess the response of the water-table, a comparison "pristine" site is compared with downstream monitored sites. The results show huge changes in water-table levels. The study verifies that the water-table is extremely responsive to environmental flows, that strong internal similarities exist along the length of the river, and that the effect on the water-table and hence likely riparian vegetation recovery can be tentatively predicted. The actual impacts of the restoration strategy are less than those originally expected politically, socially and within the scientific community. We make recommendations on more effective release strategies. 相似文献
220.
基于InVEST-PLUS模型的碳储量空间关联性及预测——以广东省为例 总被引:2,自引:0,他引:2
构建土地利用碳储量数据库,基于InVEST模型Carbon模块,得到广东省1990~2020年碳储量时空分布情况.用Moran’s I指数和Getis-Ord Gi*分析格网尺度下碳储量时空分布特征,用Anselin Local Moran’s I得到LISA集聚图.然后运用PLUS模型和14个土地利用驱动因子预测2050年土地利用及其碳储量分布.结果表明,土地利用变化直接影响区域碳储量高低,林地、草地等具有生态服务功能地类碳密度最高,分别是188.44,329.34Mg/hm2.碳储量空间格局整体呈现出中部低、北部高、东西中等的特点.碳储量空间分布特征与土地利用特征一致,碳储量显著高值集聚区域分布在建设用地少、生态用地多且连片的粤北地区,显著低值区域分布在国土开发强度和生态用地破碎化程度高的珠三角地带.在自然发展情景下,到2050年广东省土地利用碳储量将减少4327.21万Mg,随着国土空间进一步开发,环珠江口沿岸城市碳储量持续下降.增加植被生态系统碳储量,是实现碳中和的重要手段之一.要继续维持粤北山区生态保护屏障的重要地位,减缓珠三角城市土地开发强度,提高建设用地集约节约能力,形成平衡协调的土地利用和碳储量格局. 相似文献