Response of Picea rubens seedlings to intermittent mist varying in acidity, and in concentrations of sulfur-, and nitrogen-containing pollutants

Two-year-old red spruce seedlings ( Picea rubens Sarg .) growing in. field chambers were repeatedly exposed to acidic mist with a factorial combination of 3 fluctuating levels of acidity: median pH values of 3.0 (range of 2.5 to 3.5), 3.5 (range of 3.0 to 4.0), and 4.0 (range of 3.5 to 4.5). and 3 ion compositions: sulfate. nitrate and ammonium, and a combination of all 3 ions. The experiment was performed during the growing season over a period of 3.5 months. Mist exposures were intermittent with 5 wet-dry cycles for each 16-h overnight exposure period, Foliar necrosis occurred on seedlings treated with the most acidic mist and was most severe when the mist contained sulfate. At a median pH of 3.5, a value close to that of cloud water occurring in the eastern United States, injury developed with sulfuric acid mist, but not. when the mist contained nitric acid. The combination of high acidity and sulfate significantly decreased volume of aboveground tissues, while high acidity and nitrate increased volume. Root and needle dry weights were not affected. However, high acidity of mist was associated with increased leader shoot length. These results indicate, that there is a risk of foliar injury and changes in growth of red spruce with cloud water at a median acidity of pH 3.5 or below, especially when there are high concentrations of sulfate and low concentrations of nitrate.     

Asexual reproduction changes predator population dynamics in a life predator–prey system

Many organisms display oscillations in population size. Theory predicts that these fluctuations can be generated by predator–prey interactions, and empirical studies using life model systems, such as a rotifer-algae community consisting of Brachionus calyciflorus as predator and Chlorella vulgaris as prey, have been successfully used for studying such dynamics. B. calyciflorus is a cyclical parthenogen (CP) and clones often differ in their sexual propensity, that is, the degree to which they engage into sexual or asexual (clonal) reproduction. Since sexual propensities can affect growth rates and population sizes, we hypothesized that this might also affect population oscillations. Here, we studied the dynamical behaviour of B. calyciflorus clones representing either CPs (regularly inducing sex) or obligate parthenogens (OPs). We found that the amplitudes of population cycles to be increased in OPs at low nutrient levels. Several other population dynamic parameters seemed unaffected. This suggests that reproductive mode might be an important additional variable to be considered in future studies of population oscillations.     

三种淡水藻类对萼花臂尾轮虫培养效果的比较

在28℃下,采用群体累积培养法,探讨了不同浓度的蛋白核小球藻（Chlorella pyrenodeosa）、水华鱼腥藻（Anabaena flas-aquae）和沙角衣藻（Chlamyclomoras sajao）,以及在等生物量条件下,以上3种藻类两两配比饵料（3：1、1：1和1：3）对萼花臂尾轮虫（Brachionus calyciflorus）的培养效果。结果表明,不同浓度的蛋白核小球藻、水华鱼腥藻和沙角衣藻对萼花臂尾轮虫增殖效果的影响分别表现为差异极显著（P〈0．01）、显著（P〈0．05）和不显著（P〉0．05）;蛋白核小球藻与水华鱼腥藻组成的混合饵料对萼花臂尾轮虫的增殖效果均优于其中的单一种类（P〈0．05）;沙角衣藻无论是单独投喂,还是与其它藻类混合投喂,轮虫的培养效果均不理想。因此,该种类不宜用作轮虫饵料开发。该研究还表明,蛋白核小球藻是培养萼花臂尾轮虫的最适单一种类,它与水华鱼腥藻组成的混合饵料培养萼花臂尾轮虫效果更好。     

维生素E对萼花臂尾轮虫繁殖的影响

15℃下 ,添加 Ve浓度为 2 0～ 80 ng/ m l时 ,种群密度与培养时间呈显著相关 ,其中 2 0 ng/ ml和 4 0 ng/ ml组最大种群密度分别为 76 .4 0 ind/ ml和 6 5 .2 0 ind/ ml,显著高于对照组 (最大密度 12 .0 0 ind/ ml)。最大混交雌体百分率低于 10 % ,对照组最大混交雌体比率为 4 0 %。轮虫卵雌比有不同程度的提高 ,但维生素浓度为 10 0 ng/ ml时 ,对种群增长不利 ;2 5℃下 ,对照组和各添加组最大密度依次为 6 8.0 0 ,12 2 .0 0 ,12 4 .0 0 ,16 8.0 0和 2 36 .0 0 ind/ ml。最大卵雌比依次为 1.2 1,1.2 5 ,1.2 2 ,1.4 1和 0 .6 9,混交雌体百分比分别为 2 7.6 9,19.89,18.4 2 ,17.0 2和 12 .88% ;30℃下 ,最大密度依次为 113.80 ,12 1.0 0 ,12 2 .80和 15 1.2 0 ind/ ml,最大卵雌比依次为 1.5 0 ,1.4 2 ,0 .6 4和 0 .96。混交雌体百分比分别为 1.76 ,32 .2 6 ,37.5 0和 32 .0 0 %。     

Effect of two microalgae concentrations on body size and egg size of the rotifer <Emphasis Type="Italic">Brachionus calyciflorus</Emphasis>

The rotifer, Brachionus calyciflorus, was grown with two algae species (Chlorella sp. and Scenedesmus obliquus) at different concentrations (0.1, 1 and 10 × 10⁶ cells ml⁻¹). The body size (lorica biovolume) of individual rotifer and their egg size were measured when the populations were roughly in the exponential phase of population growth. The body size of the rotifers differed significantly (P < 0.05) among the two algae species used, however this effect was not observed for egg size. The body size of rotifers fed on higher densities of Chlorella sp. (10 × 10⁶ cells ml⁻¹) was significantly larger than for those fed on lower and medium densities (0.1 and 1 × 10⁶ cells ml⁻¹). Body size and egg size of rotifers fed with different amounts of Scenedesmus did not differ significantly. The egg size was significantly larger at higher food level of Chlorella. A significantly positive correlation was observed between the adult rotifer body size and their egg size.     

维生素B12对萼花臂尾轮虫种群的影响

温度为15℃时,添加20,40,80和100μg/mL维生素B12后,萼花臂尾轮虫(Brachionuscalyciflorus)种群密度随时间增加而增长,其回归方程依次为:y=e(0.1757+0.2974x),y=4.6765x1.2079,y=7.7798x1.0175和y=e(0.6117+0.3469x),密度显著高于对照组(t=4.56,8.15,8.53和9.86;P1.4366,y=7.7461x1.6533,y=6.3611x1.7790和y=9.064x1.6872,对照为y=7.5902x1.50192。各添加组的密度均显著高于对照组(t值分别为16.12,10.17,5.83和5.86;P(0.1376+0.4395x),y=e(0.2032+0.4856x),y=3.4615x1.9522和y=e(0.0220+0.48074x)。对照组除了和20ng/mL组间没有统计差异外(t=0.34,P>0.05),其他各实验组密度显著高出对照组(t值分别为3.66,10.23和2.13)。最高混交率分别为18.18%,7.60%,18.18%和16.67%,对照为66.70%。最大卵雌比依次为0.70,1.90,0.91,1.09,对照组为0.95。       

两品系萼花臂尾轮虫摄食强度的比较研究

对广州和芜湖两品系萼花臂尾轮虫的摄食强度及其与食物浓度、食物种类和培养时间之间的关系进行了比较研究.结果表明,食物浓度、食物种类和培养时间均对轮虫滤水率和摄食率有显著影响.两品系轮虫滤水率和摄食率均随培养时间的延长而减小;20 h内,两品系轮虫的总滤水率均与食物浓度呈曲线相关,而两品系轮虫总摄食率均与食物浓度呈直线相关.广州和芜湖两品系轮虫均在以小球藻为食物时有较大的滤水率,分别为0.0029±0.0001和0.0039±0.0008ml·ind.^-1·h^-1;广州品系轮虫以小球藻为食物时的摄食率(0.3992×10⁴±0.00850×⁴ cell·ind.-1·h^-1)显著地大于以栅藻为食物时的摄食率(0.170×⁴±0.0370×⁴ cell·ind.^-1·h^-1),而它们均与以混合藻为食物时的摄食率无显著差异;芜湖品系轮虫摄食率不受食物种类影响.轮虫滤水率和摄食率因食物浓度、食物种类和培养时间的不同而在品系间存在着差异.     

蒙古裸腹溞与褶皱臂尾轮虫的种间关系

在实验室内将蒙古裸腹溞按0．06、0．10、0．30、0．60个·ml^-1的密度与褶皱臂尾轮虫(密度为0．3个·ml。)进行}昆合培养,同时按上述密度分别单种培养了蒙古裸腹溞和褶皱臂尾轮虫作为对照．结果表明,蒙古裸腹溞与褶皱臂尾轮虫之间存在种间竞争,当二者共存时,褶皱臂尾轮虫对蒙古裸腹溞种群产生压制作用,使蒙古裸腹溞在混合培养体系中以很低的密度存在,而褶皱臂尾轮虫种群受蒙古裸腹溞影响不大．通过进一步的饥饿实验发现90％的褶皱臂尾轮虫经过144h饥饿后仍然存活,而经过120h饥饿后的蒙古裸腹溞100％死亡,褶皱臂尾轮虫耐饥饿能力较强是其在与蒙古裸腹溞竞争中获胜的原因之一。     

不同克隆萼花臂尾轮虫的后代质量及其相关因素分析

在4个温度(15 ℃、20 ℃、25 ℃和30 ℃)下对4个不同生化遗传特征的萼花臂尾轮虫克隆(A、B、C和D)所产幼体的耐饥饿时间及其与温度、轮虫个体大小和卵大小等的关系进行研究.结果表明,15 ℃下克隆B幼体耐饥饿时间最短,为45.67 h;20 ℃和25 ℃下克隆C幼体耐饥饿时间均最长,分别为61.33 h和72.01 h;30 ℃下克隆A幼体耐饥饿时间最长,为40.11 h.4个温度间,克隆A轮虫幼体的耐饥饿时间在15 ℃下最长,克隆B和C轮虫幼体的耐饥饿时间在30 ℃下均最短,克隆D轮虫幼体的耐饥饿时间随培养温度的升高而逐步显著缩短.4个克隆轮虫的幼体耐饥饿时间均与温度呈显著负相关关系.克隆A轮虫的幼体耐饥饿时间还与卵体积呈显著负相关,克隆C相反;克隆B和克隆D轮虫幼体耐饥饿时间与个体体积呈显著正相关关系.     

镜湖萼花臂尾轮虫种群内不同基因型克隆的生活史特征

应用生命表统计学等方法,比较了15、20、25和30℃4个温度下镜湖萼花臂尾轮虫种群内13个不同基因型克隆的生命表统计学参数和后代混交雌体百分率等生活史特征．结果表明：轮虫的世代时间、平均寿命、出生时的生命期望值、内禀增长率、净生殖率和后代混交雌体百分率对升高温度的反应均因克隆的不同而存在差异;温度、克隆及两者间的交互作用对其也都具有极显著影响．表明水环境在温度等方面所具有的时间异质性可能是镜湖萼花臂尾轮虫种群丰富的遗传变异得以维持的原因之一;自然选择出现在共存的克隆中,但其强度较低或作用时间较短是克隆共存的重要原因;遗传漂变可能在种群的基因型频率变化中起重要作用．不同基因型轮虫克隆的存在对其种群在水环境中的持续存在具有重要意义．