Studies in the Hordeum murinum aggregate 1. Morphology

Morphological data has been assembled from a large collection of fruiting heads of the Hordeum murinum aggregate. Computer analysis reveals two major taxa, which, using seven characters, can be readily separated. These are recognized as H. murinum L. and H. leporinum Link. The former is primarily north-western and the latter south-eastern in distribution. Both plants can occur sympatrically, and there is no evidence of a cline.
Diploid plants from south-east Europe represent extreme H. leporinum types and these are recognized as a subspecies (H. leporinum Link ssp. glaucum (Steudel) Booth & Richards) stat. et comb. nov. Hexaploid plants of H. leporinum cannot be morphologically differentiated.     

Digestion in pycnogonids: a study of some polar forms

The process of digestion was studied in some polar pycnogonids, mainly the Antarctic forms Nymphon australe and Nymphon orcadense. Our findings did not support the theory of the digestive process proposed by Schlottke (1933) and this led to a re-examination of his ideas. We propose a new scheme for digestion in pycnogonids and fit Schlottke's observations into this framework. It is suggested that Antarctic pycnogonids may possess behavioural adaptations peculiar to their supply of food. Some directions for further study are indicated.     

Identification and characterization of QTL underlying whole-plant physiology in Arabidopsis thaliana: δ13C, stomatal conductance and transpiration efficiency

Water limitation is one of the most important factors limiting crop productivity world-wide and has likely been an important selective regime influencing the evolution of plant physiology. Understanding the genetic and physiological basis of drought adaptation is therefore important for improving crops as well as for understanding the evolution of wild species. Here, results are presented from quantitative trait loci (QTL) mapping of flowering time (a drought escape mechanism) and carbon stable isotope ratio (δ¹³C) (a drought-avoidance mechanism) in Arabidopsis thaliana. Whole-genome scans were performed using multiple-QTL models for both additive and epistatic QTL effects. We mapped five QTL affecting flowering time and five QTL affecting δ¹³C, but two genomic regions contained QTL with effects on both traits, suggesting a potential pleiotropic relationship. In addition, we observed QTL–QTL interaction for both traits. Two δ¹³C QTL were captured in near-isogenic lines to further characterize their physiological basis. These experiments revealed allelic effects on δ¹³C through the upstream trait of stomatal conductance with subsequent consequences for whole plant transpiration efficiency and water loss. Our findings document considerable natural genetic variation in whole-plant, drought resistance physiology of Arabidopsis and highlight the value of quantitative genetic approaches for exploring functional relationships regulating physiology.     

Effect of landscape factors on fish distribution in arctic Alaskan lakes

1. The distribution of species is affected by many factors operating at a variety of temporal and spatial scales in a heterogeneous landscape. In lakes, fish communities are dynamic, influenced by landscape‐level factors that control colonisation and extinction. 2. We used classification and regression tree (CART) analyses to quantify the importance of landscape‐level factors in determining the distribution of fish species in 168 arctic Alaskan lakes. Factors including lake size, depth, outflow gradient, distance to other lakes, lake order, altitude, river drainage and age of glacial surface were analysed. These factors could affect either access of fish to a lake (colonisation variables), or their survival in a lake that already had been colonised (extinction variables). 3. The presence of a species was predicted accurately in 78.4% ± 10.5% (mean ± SD) of cases, and absence in 75.0% ± 6.1% of cases. The relative importance of extinction versus colonisation variables varied with species. Extinction variables were most important for lake trout (Salvelinus namaycush) and slimy sculpin (Cottus cognatus), a mixture of extinction and colonisation variables was important for arctic char (Salvelinus alpinus), and colonisation variables were most important for arctic grayling (Thymallus arcticus) and round whitefish (Prosopium cylindraceum). 4. Ecological differences among species account for much of the difference in relative importance of colonisation versus extinction variables. In addition, stream piracy events have occurred over geologic time scales, which have resulted in lakes that are currently inaccessible but support relict fish populations. 5. Climate warming, currently occurring in the arctic, is likely to alter further the stream network, which could have dramatic effects on fish distributions by affecting access to isolated lakes or isolating lakes that are currently accessible.     

粘虫(Pseudaletia separata(Walker))生殖系统的解剖

本文内容是研究粘虫(Pseudaletia separata(Walker)生殖系统的形态构造。全文分为雄性内部生殖器、雄性外部生殖器、雌性内部生殖器及雌性外部生殖器四部分。 粘虫的雄性内生殖器中, 有睾丸一对, 左右并列, 呈扁椭圆形, 外被紫红色睾丸膜; 输精管一对, 基部膨大成二对贮精囊; 射精管分成复射精管及单射精管两部分。雄性外生殖器的构造极为复杂, 第9腹节的背、腹板分别形成马鞍状的背兜及基腹弧; 第10腹节仅有其附肢特化成钩形突、颚形突和背兜侧突等; 抱握器占雄性外生殖器中的大部分, 其顶上角具长约1毫米的端刺一枚, 此为本种特征之一, 可以此与近似种区别; 阳茎由基部球状的阳茎囊和端部柄状的阳茎端组成, 内具内阳茎及角状器:雄性外生殖器中有关器官的肌肉来源亦作了叙述。 精液是以贮存于精球的方式授入雌体, 精球分为精球体、精球柄及系带三部分。 雌性内生殖器中, 卵巢为多滋式, 一对, 各由四个卵巢管组成, 两组卵巢管再与一对侧输卵管相连, 后者通入中输卵管中, 中输卵管后端连有外生殖腔, 其外方的开口是为产卵孔; 受精囊为长形梨状物, 分成主囊及副囊两部分, 两者在顶部愈合, 并由此发出受精管与外生殖腔相通, 在主囊顶端有受精囊腺; 附腺一对, 与附腺囊相连, 后者通入附腺主囊, 并由此开口入外生殖腔。雌性外生殖器是由交配囊和产卵器组成, 前者复可分成囊导管、囊体及囊颈三部分, 其外方的开口为交配囊孔, 有导精管从囊颈连于外生殖腔; 产卵器由第8、9腹节组成, 非呈特殊构造。     

THE FAILURE OF PHENOL TREATED ESCHERICHIA COLI TO GROW ON MEMBRANE FILTERS

SUMMARY: Counts of Escherichia coli were done on nutrient agar (control), on membrane filters on nutrient agar and on membrane filters on filter paper pads. With untreated bacteria counts were similar under all conditions, though membrane filters on nutrient agar tended to give slightly low counts. Phenol treated bacteria gave much lower counts when membrane filters were used: the mean counts for 3 strains of the test organism with filters on nutrient agar varied from 35–65% of the control, while counts with filters on filter paper pads were somewhat lower, varying from 30–47% of the control. The low counts on membrane filters on filter paper pads were not due to adsorption of phenol by the filters or to a low concentration of nutrients in the growth medium.     

NILE BLUE, ANILINE BLUE AND NEUTRAL RED AS INDICATORS OF LIPOLYSIS

SUMMARY: Dyes which have been used to detect lipolysis (Nile Blue, Aniline Blue and Neutral Red) and others (Methylene Blue, Toluidine Blue and Thionin) were critically examined for their inhibitory effects in both liquid and solid media. It was confirmed that Nile Blue would inhibit the Gram-positive bacteria tested, even at 2 × 10⁻⁵. Gram-negative bacteria were not inhibited at 1 × 10⁻⁴ and the colour change in fat media was good. Aniline Blue and Neutral Red did not inhibit Gram-positive organisms at 1 × 10⁻⁴ and the colour change was moderately good. The other three dyes were not toxic at 2·5 × 10⁻⁵, but there was no colour change. When butter fat saturated with the precipitated bases of Nile Blue, Basic Fuchsin, Crystal Violet or Malachite Green was incorporated in peptone-Yeastrel agar, the resulting media were toxic to Gram-positive bacteria. Fat saturated with the bases of Aniline Blue or Neutral Red permitted growth, but the colour change with lipolytic species was not striking, being one of intensity only. Satisfactory growth and colour changes were obtained using butter fat stained with the inert dye Waxolene Green in medium containing Neutral Red in the aqueous phase, and with butter fat stained with the oxazine base of Nile Blue in agar containing Aniline Blue.