叶绿素荧光动力学参数的意义及讨论

叶绿素荧光动力学技术被称为研究植物光合功能的快速、无损伤探针。但其参数众多，且名称及在参数的生物学意义解释上存在不规范和混乱现象。本文通过对这些问题的讨论旨在引起使用者的注意，并探讨正确使用这些参数的途径     

藏汉通婚子代的肤纹参数研究＊

本文首次较为完整地报道了藏汉通婚子代群体的14项肤纹参数（其中藏父汉思及汉父藏母各100 例），并将这些肤纹参数分别与其藏汉父母样本的有关肤纹参数进行比较，再与1000例藏族及1040例 汉族两个大样本的有关肤纹参数进行比较。结果表明：藏汉后代的肤纹特征介于藏族和汉族之间，提示 肤纹参数的多因子遗传本质。     

多个数量性状的拓广遗传参数

运用多元分析方法定义了拓广表型方差(?)(generalized phenotypic variance),拓广遗传方差(?)(generalized genetic variance),拓广遗传力(?)(generalized heritability)和拓广遗传相关系数(?)(generalized genetic correlation coefficient): 这些参数可用来对多个数量性状总体的变异、协变异及不同组向量之间的相关性进行轮廓分析(profile analysis)。用棉花和紫花苜蓿的两个实例说明了这些参数的估算和应用。     

福建沙溪口水电站库区混合输移参数研究

本文以沙溪口水电站水库为例,对河道式水库混合输移参数的识别作了若干研究。阐述示踪实验确定这些参数的原理、方法,提供沙溪口电站库区河段枯水期的参数值。在示踪实验基础上,提出适用于水电站不同运行状态混合输移参数的估算公式。可为有关部门研究水环境容量,制订水质规划等提供参考。     

儿童的惯性－惯量特征及其生长

本文应用排水法得到儿童肢体沿长轴的体积分布函数。根据关于人类肢体体积－质量的假定,肢体的质心、转动惯量及旋转半径等动力学常数可由前述的体积分布函数中求出。本文结果显示,部分力学参数与儿童的生长有着密切的联系,并受到性别的影响。因此,这些参数可以用来作为儿童的生长指标。以往数据的离散性表明,无论从系统上或技术上,这一领域都有许多工作要做。     

胶州湾生物-物理耦合模型参数灵敏度分析

参数灵敏度分析旨在评价模型中各参数对模拟结果的影响程度,是参数优化和模型校正的基础步骤,也是认识模型行为的重要工具。所建的胶州湾生物-物理耦合模型包括浮游植物、浮游动物、营养盐、碎屑和溶解氧5类状态变量,对其涉及的50个参数进行灵敏度分析,得到3个非常灵敏性参数、2个灵敏性参数、11个比较灵敏性参数和34个不太灵敏性参数。非常灵敏及灵敏性参数包括浮游植物生长速率(μPRPC)、暗反应修正因子(FAC)、光饱和强度(α)、浮游植物死亡率(μDEPC)和水体消光系数(bla),主要影响浮游植物生长和死亡过程,反映了浮游植物在生态系统中的基础性和重要性作用。这5个参数显著地影响碳和营养盐循环,是整个胶州湾生态系统最主要的影响参数,应优先进行优化。比较灵敏性参数的影响主要表现在营养盐对浮游植物生长或死亡的限制以及温度对光饱和量的限制,浮游动物生长、牧食和死亡过程以及浮游植物生物量对牧食的限制,叶绿素a的生产,缺氧条件下沉积物释放磷以及浮游植物对磷的摄取等过程,这些参数对于各状态变量的灵敏性存在不同程度的差异,从而表征不同的特点。与不太灵敏性参数相关的过程主要为叶绿素a和碎屑消光作用,温度对浮游植物生长、浮游动物牧食、碎屑和沉积物矿化的限制,碎屑和沉积物矿化与沉降,与无机氮相关的大部分过程,溶解氧浓度变化等,这些过程除了受模型内部参数影响外,还在很大程度上受水深、海水温度和陆源污染等外部因素影响。比较灵敏及不太灵敏性参数影响模型局部过程,是模型校正的重要依据,除了非常灵敏及灵敏性参数以外,叶绿素a、浮游动物、碎屑和无机磷四种状态变量可分别根据叶绿素a最大生产系数(K CHmax)、浮游动物一级死亡率(μDEZC1)、有机碎屑矿化率(μREDC)和浮游植物磷摄取的半饱和常数(h UPPP)进行校正。与营养盐相关参数的灵敏度分析表明,胶州湾浮游植物处于磷限制,无机氮主要受陆源排污影响。因此,对无机氮的校正主要通过合理设置沿岸河流径流量或陆源污染物浓度与比例以及无机氮初始场。溶解氧对各参数均不太灵敏。     

儿童的惯性－惯量特征及其生长

本文应用排水法得到儿童肢体沿长轴的体积分布函数。根据关于人类肢体体积－质量的假定，肢体的质心、转动惯量及旋转半径等动力学常数可由前述的体积分布函数中求出。本文结果显示，部分力学参数与儿童的生长有着密切的联系，并受到性别的影响。因此，这些参数可以用来作为儿童的生长指标。以往数据的离散性表明，无论从系统上或技术上，这一领域都有许多工作要做。     

正廿面体病毒衣壳参数的研究

本项研究从多学科的不同角度出发,对正廿面体病毒衣壳参数进行了深入研究.整理和开发出衣壳参数50多个,对其每一个参数的概念、含义、来源、参数值和参数间的关系作了明确的认定,并阐述了衣壳参数的理论意义及其应用价值.     

植物水分生理研究中的压力-容积测定技术几个关键问题

传统的压力-容积(pressure-volume,PV)技术是通过测定植物组织细胞从吸水饱和状态直至膨压消失的失水全过程中水势与相对含水率,并建立两者之间的关系,从而获得其他方法难以获取的植物水分生理参数(如:质壁分离渗透势、饱和渗透势、质壁分离相对含水量、细胞弹性模量)。这些参数与植物耐旱性密切关联,反映植物组织在干旱期维持功能的能力,因而使该技术在揭示树木因水力衰竭而死亡的生理机制中发挥重要作用。然而,该技术在试验材料预处理、测定、计算方法等关键步骤上尚存在问题。为此,本文针对这些潜在问题,结合中国应用研究现状,对PV技术进行综述,并提出相应的建议。     

大豆不同亲本类型F2主要性状遗传参数分析

对大豆3个不同亲本类型的杂交组合F2群体主要性状遗传变异系数、遗传力和遗传进度进行了估算分析,结果表明：这些遗传参数因性状或亲本类型的不同而有明显差异。含有野生亲缘关系的组合,类型间、性状间F2遗传力有较大差异,性状变异幅度增大,相对遗传进度也较大,从而有较广泛的选择基础。     

Effects of estrogen-depletion on rat casein gene expression

Mammary tissue from rats that had been ovariectomized and adrenalectomized 4 weeks previously was compared to that from intact rats in terms of epithelial content and hormone-responsiveness in vitro. The endocrinectomy resulted in about a 30% enlargement of the gland, but led to a loss of only about 12% of the epithelium. This estrogen-depleted epithelium was able to acquire full responsiveness in vitro to insulin in terms of the accumulation of alpha-aminoisobutyric acid, and induction of glucose-6-phosphate and gluconate-6-phosphate dehydrogenases. It was also fully responsive to cortisol in relation to the induction of NADH-cytochrome C reductase, and to prolactin in terms of total RNA synthesis. However, estrogen-depletion led to an 82% loss in the ability of a unit amount of the epithelium to synthesize casein in response to these 3 hormones, and to a similar loss in relation to the accumulation of 25K casein mRNA. Estrogen administration in vivo could prevent and reverse the casein lesion. The disparity between constitutive and casein hormone-responsiveness in the absence of estrogen is discussed in relation to cell commitment.     

HETEROCHRONIC DEVELOPMENTAL PLASTICITY IN LARVAL SEA URCHINS AND ITS IMPLICATIONS FOR EVOLUTION OF NONFEEDING LARVAE

Preexisting developmental plasticity in feeding larvae may contribute to the evolutionary transition from development with a feeding larva to nonfeeding larval development. Differences in timing of development of larval and juvenile structures (heterochronic shifts) and differences in the size of the larval body (shifts in allocation) were produced in sea urchin larvae exposed to different amounts of food in the laboratory and in the field. The changes in larval form in response to food appear to be adaptive, with increased allocation of growth to the larval apparatus for catching food when food is scarce and earlier allocation to juvenile structures when food is abundant. This phenotypic plasticity among full siblings is similar in direction to the heterochronic evolutionary changes in species that have greater nutrient reserves within the ova and do not depend on particulate planktonic food. This similarity suggests that developmental plasticity that is adaptive for feeding larvae also contributes to correlated and adaptive evolutionary changes in the transition to nonfeeding larval development. If endogenous food supplies have the same effect on morphogenesis as exogenous food supplies, then changes in genes that act during oogenesis to affect nutrient stores may be sufficient to produce correlated adaptive changes in larval development.     

Effect of heterosexual olfactory and visual stimulation on 5-en-3 beta-hydroxysteroids and progesterone in the male rat brain

Pregnenolone, dehydroepiandrosterone and progesterone were measured in specific areas of the brain and in the retina of young adult male rats exposed to the scent or to the scent and view of young cycling females and compared to the levels obtained in males similarly exposed to other males (control). All the steroid values observed were much higher than those found in plasma, varied considerably from one area to another and responded sometimes in opposite directions to stimulation of young adult males by the scent or by the scent and view of cycling females. In male rats exposed to the scent of young cycling females pregnenolone decreased significantly only in the olfactory bulb in comparison with the controls. There were no significant changes in dehydroepiandrosterone or progesterone in this case. When male rats were exposed to the scent and view of female rats, pregnenolone again decreased significantly in the olfactory bulb while dehydroepiandrosterone increased significantly in the olfactory bulb and the retina and progesterone decreased significantly in the hypothalamus, amygdala and parietal cortex. These results are discussed in relation with a possible new role for certain steroids in neuroregulatory mechanisms related to behaviour.     

Periodicity in the rise and fall of the numbers of the principal Staphylococcus aureus phage groups

The results of the phage typing of 5, 168 Staph. aureus strains isolated in a surgical hospital between 1959 and 1977 are analyzed for each year of this period. The wave of increase in the number of staphylococci belonging to phage group II which began, as discovered in this study, in 1965 and still showed no tendency towards decrease in 1977, as well as the periodicity of rises and falls in the number of staphylococci belonging to phage groups I and III are discussed and compared with the data contained in the literature. The authors come to the conclusion that Staph. aureus is subject to wave-like rises and falls in the number of strains belonging to the main phage groups of the species, and among them the strains belonging to phage groups I and III seem to be inversely related in respect of rises and falls in number, such changes occurring periodically at an interval of 10-12 years, while in the strains belonging to phage group II changes in number occur at a slower rate. The constant account of the percentage of phage groups I, II and III is recommended to ensure rational antibiotic therapy.     

Comparative ungulate dynamics: the devil is in the detail

Attempts to relate species differences in population dynamics to variation in life histories rely on the assumption that the causes of contrasts in demography are sufficiently simple to be derived from first principles. Here, we investigate the causes of contrasts in dynamics between two ungulate populations on Hebridean islands (red deer and Soay sheep) and show that differences in stability, as well as in the effects of variation in density and climate, are related to differences in timing of reproduction relative to seasonal variation in resource abundance. In both populations, attempts to predict changes in population size sufficiently accurately for the results to be useful for management purposes require a knowledge of the responses of different age and sex categories to changes in density and climate, as well as of population structure.     

Using genetically engineered mice for radiation research

The laboratory mouse has been used for many decades as a model system for radiation research. Recent advances in genetic engineering now allow scientists to delete genes in specific cell types at different stages of development. The ability to manipulate genes in the mouse with spatial and temporal control opens new opportunities to investigate the role of genes in regulating the response of normal tissues and tumors to radiation. Currently, we are using the Cre-loxP system to delete genes, such as p53, in a cell-type specific manner in mice to study mechanisms of acute radiation injury and late effects of radiation. Our results demonstrate that p53 is required in the gastrointestinal (GI) epithelium to prevent radiation-induced GI syndrome and in endothelial and/or hematopoietic cells to prevent late effects of radiation. We have also used these genetic tools to generate primary tumors in mice to study tumor response to radiation therapy. These advances in genetic engineering provide a powerful model system to dissect both the mechanisms of normal tissue injury after irradiation and the mechanisms by which radiation cures cancer.     

Respiration and microflora of the rhizosphere soil of wheat influenced by foliar application of urea

The numbers of micromycetes and bacteria were investigated with respect to oxygen consumption in the rhizosphere soil of wheat and in non-rhizosphere soil. Plants after foliar application of urea (2 % solution) and non-treated plants were cultivated in degraded chernozem and garden soil in a green-house. Changes in oxygen consumption by the suspensions of rhizosphere and non-rhizosphere soils corresponded to changes in the number of bacteria designated as the rhizosphere effect (R/S). Values of R/S depended on the presence of organic substrates. Changes in oxygen consumption by the soil suspension from the rhizosphere of wheat occurring due to foliar application of urea corresponded to changes in the amount of microflora. The results obtained are discussed with respect to a possible utilization of the data to follow metabolic activity of soils in a natural environment (in situ) determined according to oxygen consumption by a soil suspension, and to assess changes in the microflora of rhizosphere and non-rhizosphere soil.     

Sporophytic response to pollen selection for Alachlor tolerance in maize

In order to assess the efficiency of male gametophytic selection (MGS) for crop improvement, pollen selection for tolerance to herbicide was applied in maize. The experiment was designed to test the parallel reactivity to Alachlor of pollen and plants grown in controlled conditions or in the field, the response to pollen selection in the sporophytic progeny, the response to a second cycle of MGS, and the transmission of the selected trait to the following generations. The results demonstrated that pollen assay can be used to predict Alachlor tolerance under field conditions and to monitor the response to selection. A positive response to selection applied to pollen in the sporophytic progeny was obtained in diverse genetic backgrounds, indicating that the technique can be generally included in standard breeding programs; the analysis of the data produced in a second selection cycle indicated that the selected trait is maintained in the next generation.     

Novel Application of Confocal Laser Scanning Microscopy and 3D Volume Rendering toward Improving the Resolution of the Fossil Record of Charcoal

Variations in the abundance of fossil charcoals between rocks and sediments are assumed to reflect changes in fire activity in Earth’s past. These variations in fire activity are often considered to be in response to environmental, ecological or climatic changes. The role that fire plays in feedbacks to such changes is becoming increasingly important to understand and highlights the need to create robust estimates of variations in fossil charcoal abundance. The majority of charcoal based fire reconstructions quantify the abundance of charcoal particles and do not consider the changes in the morphology of the individual particles that may have occurred due to fragmentation as part of their transport history. We have developed a novel application of confocal laser scanning microscopy coupled to image processing that enables the 3-dimensional reconstruction of individual charcoal particles. This method is able to measure the volume of both microfossil and mesofossil charcoal particles and allows the abundance of charcoal in a sample to be expressed as total volume of charcoal. The method further measures particle surface area and shape allowing both relationships between different size and shape metrics to be analysed and full consideration of variations in particle size and size sorting between different samples to be studied. We believe application of this new imaging approach could allow significant improvement in our ability to estimate variations in past fire activity using fossil charcoals.     

Evaluating spatial within plot crop variability for different management practices with an optical sensor?

Subsoil constraints to root growth exacerbate frequent water and nutrient limitations to crop yields in Mediterranean-type environments. Amelioration of subsoil constraints can relieve these limitations by opening root-access to subsoil water and nutrients. However, decisions in subsoil amelioration are hampered by seasonally variable yield responses in these environments. We used the APSIM model to analyse the impact of subsoil constraints on yield and yield variability. The simulated yield data were used to calculate the financial benefits of subsoil amelioration across several scenarios. There was a strong yield-dependence on accessible soil water governed by root depth. Root depth development was limited to a minimum of either the effect of subsoil constraints or the weather-dependent depth of the soil wetting front. Insufficient rainfall in dry years or in a drier region often resulted in shallow soil wetting fronts and correspondingly shallow roots even in the absence of subsoil compaction. In these situations, there is little response to subsoil amelioration. Positive yield responses and positive financial returns to subsoil amelioration are therefore greater in good rainfall years and are more likely in a wetter region. A yield response to amelioration is also greater in coarser textured sand than finer textured sandy loam in an average rainfall season because the same amount of rainfall results in a deeper wetting front in sand than in sandy loam. Hence, roots in a sand are required to grow deeper compared to a sandy loam to access the same amount of water and therefore benefited more from subsoil amelioration in an average rainfall year. In wet years, sands leach more nitrate than sandy loam, which decreases yields and the response to subsoil amelioration in sands is more than in the sandy loam. Environmental threats occur along with yield loss when roots cannot access subsoil water. These include increased nitrate leaching and deep drainage due to unused water remaining in the soil profile. By allowing roots to access deep soil water, ameliorating subsoil is expected to yield financial gains in average to good rainfall seasons and decrease the environmental risk of drainage and leaching loss. The financial gains are expected to offset potential financial losses in dry and dry finish seasons especially in coarser textured soils and wetter environment. Responsible Editor: Jan Vos.