怀山药类原球茎的诱导形成与植株再生

为提高山药离体繁殖的速度, 缩短繁殖周期, 以铁棍山药(Dioscorea opposita cv. ‘Tiegun’)带腋芽茎段为材料, 对类原球茎的诱导、增殖、分化与植株再生进行了研究。结果表明, 铁棍山药类原球茎诱导的最适培养基为MS+1.0 mg·L^-1 TDZ+30 g·L^-1蔗糖, 增殖的最适培养基为MS+9 mg·L^-1 6-BA+30 g·L^-1蔗糖, 分化的最适培养基为MS+2 mg·L^-1 KT+0.02 mg·L^-1 NAA+30 g·L^-1蔗糖, 最适生根培养基为1/4MS+0.05 mg·L^-1 NAA+1.0 mg·L^-1 PP333+15 g·L^-1蔗糖, 生根率达80%, 移栽成活率可达85%。类原球茎的诱导形成及植株再生体系的建立为怀山药种苗的快速繁殖提供了一条新途径。     

Improved enzymatic two-phase biotransformation for (R)-phenylacetylcarbinol: Effect of dipropylene glycol and modes of pH control

An octanol/aqueous two-phase process for the enzymatic production of (R)-phenylacetylcarbinol (PAC) has been investigated further with regard to optimal pH control and replacement of 2.5 M MOPS buffer by a low cost solute. The specific rate of PAC production in the 2.5 M MOPS system controlled at pH 7 was 0.60 mg U^-1 h^-1 (reaction completed at 34 h), a 1.6 times improvement over the same 2.5 M MOPS system without pH control (0.39 mg U^-1 h^-1 at 49 h). An improved stability of PDC was evident at the end of biotransformation for the pH-controlled system with 84% residual carboligase activity, while 23% of enzyme activity remained in the absence of pH control. Lowering the MOPS concentration to 20 mM resulted in a lower benzaldehyde concentration in the aqueous phase with a major increase in the formation of by-product acetoin and three times decreased PAC production (0.21 mg U^-1 h^-1). Biotransformation with 20 mM MOPS and 2.5 M DPG as inexpensive replacement of high MOPS concentrations provided similar aqueous phase benzaldehyde concentrations compared to 2.5 M MOPS and resulted in a comparable PAC concentration (92.1 g L^-1 in the total reaction volume in 47 h) with modest formation of acetoin.     

白檀离体快繁技术

以白檀(Symplocos paniculata)幼嫩茎段为实验材料, 通过对启动培养、增殖、生根培养及移栽的影响因子进行研究, 初步建立了白檀的组织培养体系。结果表明: 白檀外植体最适灭菌方案为0.1%升汞3分钟, 无菌苗获得率达81%; 最适初代启动培养基为1/2MS+30 g∙L^-1蔗糖+8 g∙L^-1琼脂, 出芽率达86.83%; 增殖最适培养基为1/2MS+1.0 mg∙L^-1 6-BA+0.02 mg∙L^-1 IBA+30 g∙L^-1蔗糖+8 g∙L^-1琼脂, 增殖系数达3.57; 最适生根培养基为WPM+0.5 mg∙L^-1 IBA+0.5 mg∙L^-1 NAA+20 g∙L^-1蔗糖+2 g∙L^-1 AC+8 g∙L^-1琼脂, 生根率达93%; 炼苗后, 移入园土:草炭土=1:1 (v/v)的基质中, 成活率达83%。     

绒毛白蜡体胚诱导和植株再生

该文探讨了基本培养基、外植体、培养条件以及植物生长调节剂配比对绒毛白蜡(Fraxinus velutina)体胚诱导的影响。结果表明,胚根是诱导体胚发生的最佳外植体;体胚诱导的最适培养基为改良MS+2 mg·L~(–1) 6-BA+0.1 mg·L~(–1) NAA、30g·L~(–1)蔗糖、5.0 g·L~(–1)琼脂;暗培养20天后进行光照培养(14小时光照/10小时黑暗),光密度为100~(–1)20μmol·m~(–2)·s~(–1),昼温度(25±2)°C,夜温度(18±2)°C;成功诱导出体细胞胚并获得再生植株,体胚诱导率可达59.8%,体胚萌发率达81.2%。壮苗最适培养基为改良WPM+0.5 mg·L~(–1) 6-BA+0.2 mg·L~(–1) ZT+0.01 mg·L~(–1) NAA。生根最适培养基为改良1/2MS+1.0 mg·L~(–1)IBA+0.05 mg·L~(–1) NAA+20 g·L~(–1)蔗糖,生根率高达97.3%,试管苗移栽成活率达97.8%。     

The potential role of microzooplankton in a northwestern Australian pelagic food web

The role of microzooplankton in waters adjacent to Australia's North West Cape (21°49'S 114°14'E) was studied during the austral summers 1997/1998 and 1998/1999. We estimated microzooplankton abundance and biomass at a shallow (∼20 m) shelf station and at a shelf break station (∼80 m). Microzooplankton were placed into six categories: four ciliate groups (strombidiids, strobilidiids, tintinnids, “other ciliates”), dinoflagellates, and sarcodines. Total microzooplankton abundances ranged between 0.14×10³ l^-1 and 3.4×10³ l^-1. The most abundant groups were the dinoflagellates (mean 459±73 standard error l^-1) and strombidiids (mean 334±42 standard error l^-1). Total microzooplankton biomass ranged between 0.03 and 1.70 µg C l^-1 (mean 0.33±0.05 standard error l^-1). Redundancy analysis indicated differences in microzooplankton community composition between stations and sampling years but no differences with sampling depth. The microzooplankton community showed considerable variability between adjacent sampling dates, reinforcing the conclusion of earlier studies that this area is a dynamic environment. Ciliate production on the shelf was estimated to be 1.05 µg C l^-1day^-1 (∼20 mg C m^-2day^-1) and 0.79 µg C l^-1day^-1(∼70 mg C m^-2day^-1) at the shelf break. Ciliate production near North West Cape was two- to six-fold higher than the rate of secondary production by juvenile copepods. Despite this, ciliate grazing appears to account for only ∼5% of primary production and ciliates do not appear to be a major conduit between primary producers and higher trophic levels in these waters.     

粉美人萱草的快繁技术和大田种植

以粉美人萱草(Hemerocallis fulva cv. ‘Fenmeiren’)的花茎为外植体进行离体培养, 该研究成功建立了粉美人萱草组培快繁技术。结果表明, 6月获得的外植体用浓度为15% (v/v)的次氯酸钠溶液消毒8分钟, 外植体存活率达95%; 最佳增殖培养基为MS+1.0 mg·L^-1 6-BA+0.004 mg·L^-1 TDZ+0.1 mg·L^-1 NAA, 培养30天后, 月增殖系数达2.9; 壮苗培养基为MS+0.1 mg·L^-1 6-BA+0.1 mg·L^-1 IBA, 在该培养基中, 组培苗不再分化, 长势健壮; 最佳生根培养基为1/2MS+0.4 mg·L^-1 IBA+20 g·L^-1蔗糖, 生根率达95%; 移栽基质采用珍珠岩:草炭=1:2 (v/v), 通过精细化管理, 成活率可达85%, 出圃合格率为75%。目前已实现规模化繁殖, 并生产组培苗2.0×10⁵株, 大田种植表现良好。     

Temporal pattern in swimming activity of two fish species (Danio rerio and Leucaspius delineatus) under chemical stress conditions

Circadian periodicity of swimming activity was investigated in two fish species, the zebrafish (Danio rerio) and the sunbleak (Leucaspius delineatus) under sublethal long-term exposure to the cyanobacteria toxin microcystin-LR (nominal concentrations of 0.5 μg l^- 1, 5 μg l^- 1, 15 μg l^- 1, 50 μg l^- 1) in 15-litre tanks. Swimming activity of fish was monitored continuously by using an automated video-monitoring and object-tracing system over a period of 17 days. Influenced by long-term exposure to microcystin-LR, Leucaspius delineatus reversed their significant diurnal swimming activity and the fish became statistically significant nocturnal. Danio rerio remained diurnal active, but a significant phase shift was registered. In both Danio rerio and Leucaspius delineatus analysis of time series by cosinor regression revealed microcystin-LR induced dose-dependent alterations of the mean of oscillation, amplitude, acrophase and period length in a different extent. For Danio rerio the periodogram analysis revealed a significant circadian component of swimming activity for control as well as exposure groups, whereby the spectral amplitude clearly decreased at microcystin-LR concentrations of 15 and 50 μg l^- 1. For Leucaspius delineatus the amplitude of circadian rhythm was decreased at all exposure concentrations of MC-LR. Furthermore the dominance of circadian rhythm was clearly reduced, whereas the rate of ultradian rhythms increased at elevated MC-LR concentrations of 5 μg l^- 1, 15 μg l^- 1 and 50 μg l^- 1. The studied temporal aspects of behaviour clearly indicated stress symptoms in both fish species, therefore it proved to be a relevant method to characterise the impact of toxic substances in the environment and for biomonitoring.     

莲的离体快速繁殖技术

以莲(Nelumbo nucifera)授粉后18天的莲子胚芽为外植体,通过初代培养、继代培养和炼苗移栽,建立了莲离体快速繁殖体系。结果表明,将胚芽外植体诱导出无菌苗的最适初代培养基为MS固体培养基添加0.5 mg·L–1 6-BA、0.5 mg·L–1NAA、30 g·L–1蔗糖、0.5 g·L–1活性炭和0.8 g...     

野生红花白芨再生体系的建立和优化

以野生红花白芨成熟蒴果为外植体,建立了白芨植株的再生体系。结果表明：白芨种子萌发最佳培养基为1/2 MS+6-BA 1.0 mg·L^-1+NAA 0.1 mg·L^-1+AC 0.5 g·L^-1;原球茎增殖最适培养基为MS+KT 1.0 mg·L^-1+NAA 0.1 mg·L^-1+AC 0.5 g·L^-1;原球茎分化培养基为MS+6-BA 0.5 mg·L^-1+KT 1.0 mg·L^-1+NAA 0.1 mg·L^-1+AC 0.5 g·L^-1;不定芽增殖最佳培养基为MS+6-BA 0.5 mg·L^-1+KT 1.0 mg·L^-1+NAA 0.1 mg·L^-1+AC 0.5 g·L^-1 +土豆汁150 g·L^-1,30 d后的芽增殖率达343%;最适生根培养基为1/2MS+IBA 0.5 mg·L^-1+AC 0.5 g·L^-1+土豆汁100 g·L^-1,生根率达100%;试管苗移栽的最佳方式是以水苔+树皮+椰糠+锯木粉(2∶2∶1∶1,V/V/V/V)为混合基质进行多株移栽,成活率可达99%。     

Beta-naphthoflavone inhibits the induction of hepatic oestrogen-dependent proteins by 17alpha-ethynylestradiol in mosquitofish (Gambusia holbrooki)

The interactive effects of an aryl hydrocarbon receptor (AhR) agonist and of a xenoestrogen on biomarker responses were studied in the liver of male mosquitofish (Gambusia holbrooki). Hepatic 7-ethoxyresorufin O-deethylase (EROD) enzymatic activity was measured as a biomarker of exposure to the model AhR agonist beta-naphthoflavone (bNF). Hepatic proteins indicating the exposure of males to the synthetic oestrogen 17alpha-ethynylestradiol (EE2) were monitored by Western blot analysis using immunoserum prepared for this study. After a semi-static exposure only to waterborne EE2, Western blot analysis of liver homogenate revealed the induction of two protein bands (a double band at 205 kDa and a single band at 125 kDa). The interaction between bNF and EE2 was investigated by analysing, on the one hand, EROD activity and, on the other hand, immunoreactivity corresponding to the two oestrogen-dependent protein bands in the liver of fish exposed to different concentrations of bNF for 2 days, then to the same concentrations of bNF plus 0.1 µg l^-1 EE2 for 5 days. EE2 changed neither the basal activity of EROD nor its rate of induction with 1.0 and 4.0 µg l^-1 bNF. On the other hand, the induction of oestrogen-dependent proteins with 0.1 µg l^-1 EE2 was inhibited by exposure to 4.0 µg l^-1 bNF. These results together with literature data suggest that field monitoring of xenoestrogen contamination through the analysis of oestrogen-dependent protein in male fish as a biomarker should take into account the possible negative interference of AhR agonists.     

樟叶越桔细胞悬浮培养条件的优化

为了提高樟叶越桔(Vacciniumdunalianum)悬浮培养细胞的生物量,以樟叶越桔叶片愈伤组织为试材,通过单因素试验探究不同蔗糖浓度、培养基pH值、培养基体积、初始接种量和摇床转速对悬浮培养细胞生长的影响,并根据响应面法Box-Behnken试验设计原理进行组合试验以优化培养条件。结果显示,以改良WPM培养基为基础培养基,樟叶越桔细胞悬浮培养的最优条件为40 g·L^–1蔗糖、培养基pH5.2、培养基体积45 mL、初始接种量2.64 g和摇床转速为149 r·min^–1,其细胞生物量干重为0.184 4 g,与理论预测值0.184 5 g较为接近,且细胞的生长曲线呈S型。研究结果为樟叶越桔悬浮培养细胞次生代谢产物的生产调控奠定了技术基础。     

芍药花药愈伤组织诱导及体细胞胚发生

以芍药(Paeonia lactiflora)品种粉玉奴花药为外植体,研究不同浓度2,4-D对愈伤组织诱导、体胚发生及植株再生的影响,采用组织细胞学方法观察愈伤组织以及体细胞胚发育过程,采用根尖染色体法鉴定再生植株倍性。结果表明,芍药花药愈伤组织诱导的最适培养基为MS+1 mg·L–1 2,4-D+1 mg·L–1 N...     

巢湖春夏季节浮游植物的动态变化

2009年3月至8月,利用原位围隔实验和野外调查,研究了巢湖春夏季节浮游植物的动态变化.结果显示:围隔中浮游植物密度和生物量的变动范围分别是(2.95～102.43)×10⁵ cells·L^-1和0.0-7.39 mg·L^-1,优势种类为鱼腥藻属(Anabaena)、梅尼小环藻(Cyclotella meneghiniana)和圆筒锥囊藻(Dinobryon cylindricum),其最大生物量分别为0.82 mg·L^-1、0.66mg·L^-1和2.98 mg·L^-1,均出现在3月或4月.在巢湖湖水中,春季(3～5月)浮游植物平均生物量为5.43mg·L^-1,其中绿藻占47.59%、硅藻占40.81%、蓝藻占10.18%,优势种类为盘星藻属(Pediastrum)和梅尼小环藻;而夏季(6～7月)浮游植物平均生物量为7.89mg·L^-1,其中蓝藻占58.7%、绿藻占2.77%、硅藻占11.4%,优势种类为微囊藻属(Microcystis).磷和枝角类滤食对巢湖春夏季节浮游植物的生物量和群落结构有重要影响.     

不同诱导子对怀牛膝细胞生长及多糖含量的影响

为提高怀牛膝(Achyranthes bidentata)悬浮培养细胞中牛膝多糖的含量,以酵母提取物、榆黄蘑(Pleurotus citrinopileatus)及水杨酸作为诱导子,分别在同一时期以不同浓度或在不同时期以相同浓度添加至细胞培养物中,收获时测定细胞生长量和牛膝多糖含量。结果显示,在培养12天时添加2.5%(v/v)酵母诱导子,细胞干重最大,可达46.75 g·L–1,多糖含量为5.76 mg·g~(–1);在培养9天时添加5 mg GE·L–1榆黄蘑诱导子,收获时细胞中多糖含量可达6.56 mg·g~(–1),细胞干重达28.3g·L–1;1 mg·g~(–1)水杨酸对牛膝多糖的诱导效果不如以上2种诱导子明显。     

Stoichiometric characteristics of carbon,nitrogen and phosphorus of Sibiraea angustata shrub on the eastern Qinghai-Xizang Plateau

Aims Little is known about the stoichiometric characteristics of carbon (C), nitrogen (N) and phosphorus (P) in plateau shrubs across China. Sibiraea angustata is a typical and representative shrub species on the eastern Qinghai- Xizang Plateau, and exploring its C, N and P distribution patterns and stoichiometric properties in different organs (including root, shoot, leaf, twig and fruit) would help us better understand the mechanisms of C, N and P cycling and balance in the S. angustata dominated shrub ecosystem.
Methods Sixteen sampling sites were selected on the eastern Qinghai-Xizang Plateau by the stratified sampling method. The height and coverage of the dominant shrubs, latitude, longitude and altitude of the sites were recorded. Three 5 m × 5 m plots were selected at each site. At least 128 biological samples of plant organs of S. angustata were collected and measured, respectively. The C and N concentrations of plant samples were analyzed using an elemental analyzer (2400 II CHNS). The P concentration was analyzed using the molydate/ascorbic acid method after H₂SO₄-H₂O₂ digestion.
Important findings The C, N and P concentrations of different organs followed the order of: shoot (495.07 g·kg^-1) > twig (483.37 g·kg^-1) > fruit (480.35 g·kg^-1) > root (468.47 g·kg^-1) > leaf (466.33 g·kg^-1); leaf (22.27 g·kg^-1) > fruit (19.74 g·kg^-1) > twig (7.98 g·kg^-1) > shoot (4.54 g·kg^-1) > root (4.00 g·kg^-1) and fruit (2.85 g·kg^-1) > leaf (1.92 g·kg^-1) > twig (0.96 g·kg^-1) > root (0.52 g·kg^-1) > shoot (0.45 g·kg^-1), respectively. The ranges of the coefficient of variation (CV) for C, N and P concentrations were 1.71%-4.44%, 14.49%-25.50% and 11.46%-46.15%, respectively. Specifically, the C concentration was relatively high and stable, and the maximum CV values for N and P were found in roots. The N:P value of different organs varied from 7.12-12.41 and the minimum CV for N:P was found in twig, which indicated that N:P in twig had higher internal stability. In addition, correlation analysis indicated that the C concentration was significantly negatively correlated with N and P concentrations and correlation coefficients were -0.407 and -0.342, respectively. However, N concentration had dramatically positive correlation with P concentration and the correlation coefficient was 0.814. These results also could indicate that the C, N and P stoichiometric characteristics in the S. angustata shrub accorded with the homeostatic mechanism and growth rate hypothesis to some extent, the distributions of C, N and P concentrations were closely related to the function of the organs and it should be prudent to use ecological stoichiometric ratios to judge the condition of nutrient limitation at the species level.     

Effects of nitrogen addition on soil respiration of Rhododendron simsii shrubland in the subtropical mountainous areas of China

Aims As the second largest C flux between the atmosphere and terrestrial ecosystems, soil respiration plays a vital role in regulating atmosphere CO₂ concentration. Therefore, understanding the response of soil respiration to the increasing nitrogen deposition is urgently needed for prediction of future climate change. However, it is still unclear how nitrogen deposition influences soil respiration of shrubland in subtropical China. Our objectives were to explore the effects of different levels of nitrogen fertilization on soil respiration, root biomass increment, and litter biomass, and to analyze the relationships between soil respiration and soil temperature and moisture.
Methods From January 2013 to September 2014, we conducted a short-term simulated nitrogen deposition experiment in the Rhododendron simsii shrubland of Dawei Mountain, located in Hunan Province, southern China. Four levels of nitrogen addition treatments (each level with three replicates) were established: control (CK, no nitrogen addition), low nitrogen addition (LN, 2 g·m^-2·a^-1), medium nitrogen addition (MN, 5 g·m^-2·a^-1) and high nitrogen addition (HN, 10 g·m^-2·a^-1). Soil respiration was measured by LI-8100 soil CO₂ efflux system. At the same time, we measured root biomass increment and litter biomass in each plot.
Important findings Soil respiration exhibited a strong seasonal pattern, with the highest rates found in summer and the lowest rates in winter. Annual accumulative soil respiration rate in the CK, LN, MN and HN was (2.37 ± 0.39), (2.79 ± 0.42), (2.26 ± 0.38) and (2.30 ± 0.36) kg CO₂·m^-2, respectively. Annual mean soil respiration rate in the CK, LN, MN and HN was (1.71 ± 0.28), (2.01 ± 0.30), (1.63 ± 0.27) and (1.66 ± 0.26) μmol CO₂·m^-2·s^-1, respectively, and it was 17.25% higher in the LN treatment compared with CK (p = 0.06). The root biomass increment was increased by LN, MN, and HN treatments by 18.36%, 36.49% and 61.63%, respectively, compared to CK. The litter biomass was increased by LN, MN, and HN treatments by 35.87%, 22.17% and 15.35%, respectively, compared with CK. Soil respiration exhibited a significant exponential relationship with soil temperature (p < 0.01, R² is 0.77 to 0.82) and a significant linear relationship with soil moisture at the depth of 5 cm (p < 0.05, R² is 0.10 to 0.15). The temperature sensitivity (Q₁₀) value of CK, LN, MN and HN plots was 3.96, 3.60, 3.71 and 3.51, respectively. These results suggested that nitrogen addition promoted plant growth and decreased the temperature sensitivity of soil respiration. The increase of root biomass under N addition may be an important reason for the change of soil respiration in the study area.     

赣江下游及其支流浮游甲壳动物的群落结构

2009年6月、11月和2010年4月对赣江下游浮游甲壳动物的群落结构和时空变化进行研究.共记录浮游甲壳动物21种,其中枝角类14种、桡足类7种.脆弱象鼻溞Bosmina fatalis、微型裸腹溞Moina micrura和中剑水蚤Mesocyclops sp.为优势种.赣江下游干流浮游甲壳动物的最大平均密度和生物量(11.1ind.·L^-1和0.127mg·L^-1)均出现在6月,最小值(1.59ind.·L^-1和0.01mg·L^-1)均出现在4月.袁河支流的枝角类和桡足类密度在6月(4.97±13.28ind.·L^-1和2.07±4.85ind.·L^-1)和11月(2.07±5.21ind.·L^-1和2.24±5.22ind.·L^-1)高于赣江下游干流和锦江支流.香农-威纳指数(H')和马加利夫指数(d)表明赣江下游及其支流水质为中度污染或重污染.水温和小型浮游植物生物量是影响赣江下游浮游甲壳动物密度时空变化的重要因素.     

不同地下水矿化度对柽柳光合特征及树干液流的影响

为揭示柽柳(Tamarix chinensis)光合能力及耗水特征对地下水矿化度的响应规律, 以黄河三角洲建群种——柽柳3年生植株为研究对象, 在1.2 m的潜水水位下, 模拟设置淡水、微咸水、咸水和盐水4种不同的地下水矿化度, 测定柽柳叶片光合-光响应、蒸腾速率和树干液流的日变化。结果表明: 地下水矿化度通过影响土壤盐分可显著影响柽柳光合特性及耗水性能。随地下水矿化度升高, 柽柳叶片净光合速率(P_n)、最大P_n、蒸腾速率、气孔导度、表观量子效率和暗呼吸速率均先升高后降低, 而水分利用效率(WUE)持续降低。淡水、微咸水和盐水处理下, 柽柳P_n光响应平均值分别比咸水处理降低44.1%、15.1%和62.6%; 微咸水、咸水和盐水处理下, 柽柳WUE光响应平均值分别比淡水处理降低25.0%、29.2%和41.7%。随地下水矿化度升高, 柽柳叶片光饱和点先升高后降低, 而光补偿点持续升高, 光照生态幅变窄, 光能利用率变低。淡水和盐水处理下, 柽柳P_n下降分别是非气孔限制和气孔限制引起的。柽柳树干液流速率随地下水矿化度升高而先升高后降低, 咸水处理下树干液流速率日变幅最大, 日液流量最高。淡水、微咸水和盐水处理下日液流速率平均值分别比咸水处理降低61.8%、13.1%和41.9%。咸水矿化度下柽柳有较高的光合特性, 在蒸腾耗水较严重的情况下可实现高效生理用水, 适宜柽柳较好地生长。     

Effects of groundwater salinity on the characteristics of leaf photosynthesis and stem sap flow in Tamarix chinensis

AimsThe objective of this study was to investigate the change pattern of leaves photosynthesis and stem sap flow of Tamarix chinensisin under different groundwater salinity, which can be served as a theoretical basis and technical reference for cultivation and management of T. chinensis in shallow groundwater table around Yellow River Delta.MethodsThree-year-old T. chinensis, one of the dominated species in Yellow River Delta, was selected. Plants were treated by four different salinity concentrations of groundwater—fresh water (0 g∙L^-1), brackish water (3.0 g∙L^-1), saline water (8.0 g∙L^-1), and salt water (20.0 g∙L^-1) under 1.2 m groundwater level. Light response of photosynthesis and the diurnal courses of leaf transpiration rate, stem sap flux velocity and environment factors under different groundwater salinity were determined via LI-6400XT portable photosynthesis system and a Dynamax packaged stem sap flow gauge based on stem-heat balance method, respectively.Important findings The result showed that groundwater salinity had a significant impact on photosynthesis efficiency and water consumption capacity of T. chinensis by influencing the soil salt. The net photosynthetic rate (P_n), maximum P_n, transpiration rate, stomatal conductance, apparent quantum yield and dark respiration rate increased first and then decreased with increasing groundwater salinity, while the water use efficiency (WUE) continuously decreased. The mean P_n under fresh water, brackish water and salt water decreased by 44.1%, 15.1% and 62.6%, respectively, compared with that under saline water (25.90 µmol∙m^-2∙s^-1). The mean WUE under brackish water, saline water and salt water decreased by 25.0%, 29.2% and 41.7%, respectively, compared with that under fresh water (2.40 µmol∙mmol^-1). With the increase of groundwater salinity from brackish water to salt water, light saturation point of T. chinensisdecreased while the light compensation point increased, which lead to the decrease of light ecological amplitude and light use efficiency. Fresh water and brackish water treatment helped T. chinensis to use low or high level light, which could significantly improve the utilization rate of light energy. The decrease in P_n of T. chinensis was mainly due to non-stomatal limitation under treatment from saline water to fresh water, while the decrease in P_n of T. chinensis was due to stomatal limitation from saline water to salt water. With increasing groundwater salinity, stem sap flux velocity of T. chinensis increased firstly and then decreased, reached the maximum value under saline water. The mean stem sap flux velocity under fresh water, brackish water and salt water decreased by 61.8%, 13.1% and 41.9%, respectively, compared with that under saline water (16.96 g·h^-1). Tamarix chinensis had higher photosynthetic productivity under saline water treatment, and could attained high WUE under severe water deprivation by transpiration, which was suitable for the growth of T. chinensis.     

Effects of Oxygenation on Hydrocarbon Biodegradation in a Hypoxic Environment

In 1984, an underground storage tank leaked approximately 41,000 L of gasoline into the ground water at the Naval Construction Battalion Command in Port Hueneme, CA (USA). Benzene, toluene, ethylbenzene, and xylenes (BTEX) contamination stimulated remedial action. In 1995, a ground water circulation well (GCW) and network of surrounding monitoring wells were installed. After year of operation, dissolved oxygen and nitrate concentrations remained low in all monitoring wells. Benzene utilization (the sum of respiration, uptake, and conversion to polar compounds) ranged from 0.03 to 4.6 µg L^-1 h^-1, and toluene utilization ranged from 0.01 to 5.2 µg L^-1 h^-1. Heterotrophic bacterial productivity (total carbon assimilation) increased dramatically in the GCW, although benzene and toluene utilization decreased markedly relative to surrounding wells. Benzene and toluene uptake accounted for a significant proportion (mean=22%) of the heterotrophic bacterial productivity except within the GCW, indicating other fuel contaminant or indigenous organic carbon and not BTEX compounds served as primary carbon source. The GCW effectively air-stripped BTEX compounds, but failed to stimulate benzene and toluene biodegradation and thus would not be effective for stimulating BTEX bioremediation under current deployment parameters. Air stripping was three orders of magnitude more effective than biodegradation for removing benzene and toluene in the GCW.