华北棉区棉铃虫种群动态与其为害特征分析

本文述及棉铃虫为害特性及其与为害后棉株的补偿作用关系。根据棉株生命表资料,蕾期棉株蕾花的脱落主要系由棉铃虫为害所致。而铃期蕾铃的脱落,则主要系由棉株的生理条件。在蕾期,前三周内蕾花被害脱落后,棉株的补偿作用是很高的,从第四周起补偿作用逐渐下降,而到铃期阶段时补偿作用降至很低水平。因此蕾期棉株遭受一定数量以内的棉铃虫为害,而使蕾花脱落后,反而可促使棉花增产。根据棉铃虫生命表资料,从卵期至三龄末幼虫期的累计死亡率占总死亡率的90%以上,结合幼虫死亡率与不同龄期为害水平分析,棉铃虫对棉株的主要为害阶段系在2—3龄期,其对果实的为害量占总为害的65%。而棉株被害蕾铃的田间空间分布型系遵从负二项分布,期公共K值为3.4626。     

蕾铃期繁殖器官的损失对棉花产量的影响——人工模拟为害试验

1994、1995连续两年在华北棉区第3代棉铃虫发生期间,通过一系列人工摘蕾模拟为害和人工接虫为害试验,研究了棉花对蕾铃期繁殖器官损失的补偿效应。试验结果表明：蕾、铃被害会诱导棉株产生补偿效应,即提高结铃数,增加生物产量。但棉花的补偿效应是有限的,蕾铃期单株被害蕾超过12个,被害铃超过4个,或被害超过2蕾2铃,都会导致皮棉显著减产。通过数学模型分析,1994年,单株被害0-11．80个蕾或0—2．26个铃都不会造成减产;1995年．单株损失0—10．58个蕾或0—3．8个铃,同样不会降低棉花产量。模型中各决策变量的边际产量表明,棉花蕾铃期铃的损失对皮棉产量的影响最大。     

五千亩旱地棉花早期去蕾获增产

<正> 棉株本身对于现蕾至初花期的蕾损失具有很强的补偿能力,这种补偿能力随地块的肥、水条件的改进而增强。在目前施肥水平下,有灌溉条件的高肥棉田(近三年平均亩产皮棉130斤以上),二代棉铃虫百株累计卵量三百粒以下不施药,容许二代幼虫适度为害,并在6月底不迟于7月初之前,进行人工摘蕾,使每株棉花损失(虫咬加手摘)早期蕾6—8个,可以达到省药省工又增产的目的,从而显著提高经济生态学效益,这已为1983年和1984年连续     

棉花对棉铃虫为害超补偿作用的生理机制

为研究棉花对棉铃虫为害超补偿作用的生理机制,作者在山东省滨州市棉田进行了模拟第二代棉铃虫为害的试验。结果表明：每株棉花摘除8个早蕾后,最终成铃数增加13.4%,其中下部第6及其上果枝的成铃数增加较多。处理组棉叶中可溶性糖和淀粉含量上升,氨基酸含量下降,光合作用强度加大(3.6%～6.7%),叶面积系数增加8.5%～28.1%,单株生产力增大,从而揭示了超补偿作用的重要机制。     

红铃虫为害棉花蕾、花后对成铃影响

<正> 红铃虫的第一代幼虫主要为害棉花的蕾和花。当食料不足时,幼虫被迫取食过小的花蕾致使花蕾脱落。一般情况下红铃虫为害的花蕾不会隘落,并能开花,但被害的虫花当时的脱落率明显地高于相对应的同节位的健花。1982—1983年考察,虫花与健花成铃数比较如表1。 但是在棉花生长过程中,由于棉株自身的营养分配而形成大量的自然生理脱落往往会把     

江苏沿江棉区3代棉铃虫对棉花的为害及经济阈值

通过人工接虫为害,研究了3代棉铃虫对蕾铃脱落及结铃的影响,观察了不同年份棉铃虫卵和各龄幼虫的自然存活率及棉花蕾、幼铃的成铃率。结果表明,蕾铃的虫害脱落率对结铃的影响最大,直接通径系数达－0.8917,虫量和蕾铃脱落数主要通过接虫期间的虫害脱落率影响棉花结铃,其间接通径系数分别为－0.8894和-0.891,接虫期间的自然脱落率对结铃的直接和间接通径系数均很小,表明33代棉铃虫为害时棉花4的补偿能力已基本丧失,各龄幼虫的为害量观察表明,1－6龄幼虫的单虫为害当量分别为0.02、0.14、0.31、0.47、0.84和1.54个大铃,根据防治的直接和间接收益,得出3代棉铃虫的防治指标为百株累计卵量26粒。     

氮肥对棉田主要害虫种群密度及棉花产量的影响

通过2年的田间研究,分析了3种不同施氮水平对棉花主要害虫棉玲虫、棉蚜种群动态、棉花蕾铃脱落及棉花产量的影响。结果表明,增施氮肥的棉田棉铃虫和棉蚜数量比对照田要高,但它们之间的差异没有达到显著的水平。不同年份对棉铃虫种群密度有显著影响,但对棉蚜种群没有显著影响。蕾花期施肥可减轻棉铃虫为害造成的花蕾脱落和自然脱落,增加有效铃数和产量,但增加量没有达到显著水平。     

棉花幼铃发育过程中内源激素水平的变化及赤霉酸对它的影响

为了寻求内源激素水平与棉花幼铃脱落的关系,探讨棉花幼铃发育过程中内源激素的调节作用,分别研究了正常发育的幼铃、开花当天GA_3处理的正常铃、去柱头不受精、将在开花后4～6天脱落的幼铃,以及不受精但经GA_3处理因而不脱落的幼铃在发育或脱落过程中五类内源激素水平的变化。实验结果表明,在开花当天的正常子房中,已有IAA、ABA和CTK的存在,并释放甚多Eth,GA则在开花后第6天始可测出。随着幼铃日龄增长,五类激素的含量水平各有变化。IAA的含量在第6天急骤上升,第10天达到高峰,以后下降。CTK也在第6天急骤增高,并继续平稳上升,直至实验结束。开花当天的幼铃即释放相当多的Eth,开花以后逐渐下降,正常幼铃也含有相当高的ABA。至于日龄1～5的不受精幼铃及GA_3处理不受精幼铃,其IAA和CTK两类激素的含量,在处理和对照之间,差异不大;但是不受精幼铃中ABA含量和Eth释放量的变化却十分激烈,两者在幼铃脱落前都剧烈增加,但GA_3处理不受精幼铃不出现这种急骤增长的高峰。与此相应的是GA_3有效地防止了不受精幼铃的脱落。各类内源激素在铃壳和种子中的分布是不同的。IAA和CTK是种子多于铃壳,ABA和GA则铃壳多于种子。从以上实验结果看来,幼铃中ABA和Eth水平变化与幼铃脱落是密切相关的,脱落幼铃在脱落前ABA和Eth剧烈     

棉田二代玉米螟危害损失测定及其防治对策的研究

通过1987～1988年对棉田二代玉米螟危害损失测定,表明棉花蕾花期的二代螟害对棉花产量与产值无明显影响。具体表现在螟害株单株结铃数、铃重、衣分及棉花品级等均无明显下降。二代螟害所造成的断株虽比对照健株单株皮棉下降12.24％,但断株的紧邻棉株具有与断株产量下降数相近的增铃补偿作用。由此根据当地历年棉田二代玉米螟发生情况及目前药剂防治费用等,在提出棉田二代玉米螟防治指标为蛀茎率42.13％的同时,提出正常年份对棉田二代玉米螟可不予防治或在早发棉田内实行兼治的防治对策。     

施氮量对棉株和棉铃虫的影响

用盆栽进行了不同施氮量对棉株和棉铃虫幼虫生长发育影响的试验。花期土壤施硫酸铵量分别为0、2、4和16克/盆。每盆土45斤。施氮后,土壤全氮增加,施氮量的增加提高了单株铃和叶片的干物质的累积,以及棉株不同部位的全氮含量。用含氮量显著不同的幼铃饲喂棉铃虫时,高氮食物使6龄幼虫的干重增长,同时食物利用率提高。随着饲喂铃含氮量的增长,6龄幼虫虫体和虫粪以及雌蛹的全氮含量均有所升高。 根据生物和化学两方面数据,我们认为:增施氮肥引起土壤、植株和昆虫全氮含量增长,特别是增加了棉株和棉铃虫的氮素营养。增施氮肥在一定范围内使棉株生长良好,使幼虫生长更好。由此可见:氮肥的增加可以提高棉花的产量,但也会使虫害加重。上述研究将有助于寻找大田棉花生产的氮肥合理施用量,而且对棉铃虫的有效防治有一定的参考价值。     

棉铃虫二代期模拟为害蕾的经济生态学效益

通过3年时间,在黄河流域棉区的两个不同的地点,于3种不同肥力类型的地块上,以3个不同的陆地棉品种为材料,进行了一系列的人工摘蕾模拟为害和棉铃虫自然为害的田间试验,得知土壤肥力极大地影响着棉株对于早期蕾损失的补偿能力。在肥力条件较好的地块,容许二代棉铃虫适度为害,同时辅以适当的人工摘蕾,能显著提高生态效益和经济效益。最后还给出了这一技术的应用方法。     

马尾松直径生长与气侯的非线性响应函数

在Ｆｒｉｔｔｓ响应函数基础上,提出一种树木生长对各气候变量的非线性响应函数。该响应函数把气候变量的交互作用（各气候变量乘积）之和进行合并,不仅防止了自由度的显著下降,而且还有助于了解各气候变量交互作用对树木生长的平均效应。一组马尾松芯样（１５株树,３０个芯样,位于马尾松分布带北端）经定年和除趋势后得到的年轮年表与各月平均气温、降水量的关系,经该非线性响应函数分析,表明所取马尾松对前１年１１月、当年２、５、８、９、１１月的降水量的平方有显著正响应;对前１年１２月、当年３、８、１２月的平均气温之平方有显著正响应,而对当年２月的平均气温的平方有显著负响应。     

Fleshy fungi in grass fields. Dependence on fertilization, grass species, and age of field

An experimental field with grass had 48 squares which were treated with combinations of NPK fertilizers. The fungus flora was studied 1978–1980 by numerous yearly observations. A total of 40 species were noted: 36 agarics and 4 gasteromycetes. 24 species were confined to squares where nitrate was applied. 5 of these species were recorded as fairy ring formers. The fairy rings developed exclusively in the +N squares. Some common species grew in both +N and –N squares, while a few species were confined to –N squares. None of the latter group was found in abundance. The squares were divided in parcels sown with 4 species of lawn grasses. Several fungi showed preference for one or two grass species. The field consists of two parts, sown in 1977 and 1972 respectively. The immigration pattern into the new field is described.     

Electron microscopy of glutamine synthetase from pea leaf chloroplasts

The structure of pea leaf chloroplast glutamine synthetase was studied by electron microscopy. The enzyme is shown to consist of eight elongated subunits which are arranged with point 42 symmetry at the vertices of two squares. These squares are twisted about the 4-fold axis at 40 degrees relative to each other.     

Electron microscopy of glutamine synthetase from pea leaf chloroplasts

Using electron microscopy, the spatial structure of glutamine synthetase from pea leaf chloroplasts was studied. The enzyme was shown to consist of eight elongated subunits, which are arranged with a point of 42 symmetry at the vertices of two squares. These squares are twisted about a 4-fold axis at 40 degrees relative to each other.     

用不同格数的玻板测定灭鼠效果的研究

以往报道说明,在格粉板法中,用400格玻板比用100格玻板测定灭家鼠效果更准确(赵承善等,1983)。之后,又报道用12格框架计数粉区上鼠迹所占格数,计算灭鼠率(李镜辉等,1983)。为简便400格粉板法,并对不同格数玻板的准确性进行探讨,进行了本项工作。现报道如下。     

THE ULTRASTRUCTURE OF THE Z DISC IN SKELETAL MUSCLE

This electron microscopic study deals with the structure of the Z disc of frog's skeletal muscle, with special regard to the I filaments—whether they pass through the Z disc or terminate at it. In most longitudinal sections the I filaments terminate as rod-like projections on either side of the Z disc, one I filament on one side lying between two I filaments on the opposite side. This indicates that the I filaments are not continuous through the Z disc. The rod-like projections are often seen to consist of filaments (denoted as Z filaments) which meet at an angle. In cross-sections through the Z region the I filaments and Z filaments form tetragonal patterns. The I filaments are situated in the corners of the squares; the oblique Z filaments form the sides of squares. The tetragonal pattern formed by the Z filaments is rotated 45 degrees with respect to the tetragons formed by the I filaments on both sides of Z. This structural arrangement is interpreted to indicate that each I filament on one side of the Z disc faces the center of the space between four I filaments on the opposite side of Z and that the interconnection is formed by four Z filaments.     

Susceptibility of the boll weevil to Steinernema riobrave and other entomopathogenic nematodes

The susceptibility of the boll weevil (BW), Anthonomus grandis Boheman, to Steinernema riobrave and other nematode species in petri dishes, soil (Hidalgo sandy clay loam), and cotton bolls and squares was investigated. Third instar weevils were susceptible to entomopathogenic nematode (EN) species and strains in petri dish bioassays at 30 degrees C. Lower LC(50)'s occurred with S. riobrave TX- 355 (2 nematodes per weevil), S. glaseri NC (3), Heterorhabditis indicus HOM-1 (5), and H. bacteriophora HbL (7) than H. bacteriophora IN (13), S. riobrave TX (14), and H. bacteriophora HP88 (21). When infective juveniles (IJs) of S. riobrave were applied to weevils on filter paper at 25 degrees C, the LC(50) of S. riobrave TX for first, second, and third instars, pupae, and 1-day-old and 10-days-old adult weevils were 4, 5, 4, 12, 13, and 11IJs per weevil, respectively. The mean time to death, from lowest to highest concentration, for the first instar (2.07 and 1.27days) and second instar (2.55 and 1.39days) weevils were faster than older weevil stages. But, at concentrations of 50 and 100IJs/weevil, the mean time to death for the third instar, pupa and adult weevils were similar (1.84 and 2.67days). One hundred percent weevil mortality (all weevil stages) occurred 3days after exposure to 100IJs per weevil. Invasion efficiency rankings for nematode concentration were inconsistent and changed with weevil stage from 15 to 100% when weevils were exposed to 100 and 1IJs/weevil, respectively. However, there was a consistent relationship between male:female nematode sex ratio (1:1.6) and nematode concentration in all infected weevil stages. Nematode production per weevil cadaver increased with increased nematode concentrations. The overall mean yield of nematodes per weevil was 7680IJs. In potted soil experiments (30 degrees C), nematode concentration and soil moisture greatly influenced the nematode efficacy. At the most effective concentrations of 200,000 and 400,000IJs/m(2) in buried bolls or squares, higher insect mortalities resulted in pots with 20% soil moisture either in bolls (94 and 97% parasitism) or squares (92 and 100% parasitism) than those of 10% soil moisture in bolls (44 and 58% parasitism) or squares (0 and 13% parasitism). Similar results were obtained when nematodes were sprayed on the bolls and squares on the soil surface. This paper presents the first data on the efficacy of S. riobrave against the boll weevil, establishes the potential of EN to control the BW inside abscised squares and bolls that lay on the ground or buried in the soil.     

ESTIMATION OF THE KINETIC PARAMETERS OF UNIDIRECTIONAL TRANSPORT ACROSS THE BLOOD-BRAIN BARRIER

Abstract— The unidirectional transport of metabolic substrates from blood to brain may be defined in terms of Michaelis-Menten saturable ( K m, V _max) and non-saturable ( K _d) components of influx. Various computation procedures have been previously reported to estimate the kinetic parameters when an intracarotid injection technique is used. Transformations of the influx data which allow linear plots to obtain estimates were compared with estimates obtained directly from a best fit on a least means squares criterion for both experimental and simulated data. Large discrepancies were apparent between the various estimates of the kinetic parameters when an equal weight was given to transformed data. For pyruvate (21-day-old rats), K _m, values varied between 1.02 and 6.25 mM and V _max varied between 0.68 and 2.30 μmol g⁻¹ min⁻¹. The estimates were almost equivalent when pyruvate data was re-analysed using a weighting scheme based on the finding that the absolute value of the S.D. of influx increased in proportion to influx. It is recommended that estimates of kinetic parameters be obtained by an iterative, non-linear least squares method to fit appropriately weighted data directly.