Seasonal changes in a ultraviolet structural colour signal in blue tits, Parus caeruleus

Recent studies of blue tits, Parus caeruleus , have found sexual selection and a viability-indicating function of the structural ultraviolet and blue crown plumage, but the reasons for this signal variation are not understood. Furthermore, studies in England and Sweden have yielded somewhat different results (particularly with regard to the spectral position of the reflectance peak). Here we investigate whether the blue tit UV/blue ornament varies with time of year since such variation might be relevant to the signalling function as well as the apparent difference between populations. From 400 blue tits captured at two different localities in Sweden, we found that objective measures of 'hue' (spectral location), 'chroma' (spectral purity) and 'brightness' (spectral intensity), varied substantially with season. Just after moult (October), crown 'hue' is maximally UV-shifted (359 nm for males and 373 nm for females). Thereafter the peak drifts upwards and by the time of nestling feeding (June) male reflectance peaks at 404 nm and female at 413 nm. This change is probably due to feather wear as well as fat and dirt accumulation, which might constitute an additional male quality cue. Our results suggest that it is important to consider plumage age when exploring variation in structural plumage coloration, and that it can largely explain the difference between the British and Swedish studies. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76 , 237–245.     

栖热菌属高温菌RH99-02菌株产类胡萝卜素的研究

从腾冲热海分离到最高生长温度达80℃的一株嗜热非芽孢菌RH99-02菌株,经鉴定属Thermus属,对其所产类胡萝卜素进行了吸收光谱扫描及薄层层析分析。发酵研究表明振荡培养时的菌体生物量和色素产量上均高于静置培养,培养至50h菌体生物量和色素产量达到最大值,菌体色素产量为762μg/g干重。     

青藏高原地区矮嵩草草甸植物群落生长分析

对中国科学院海北高寒草甸生态系统定位站地区的和高草草甸植物群落进行了函数生长分析研究。叶面积和地上生物量采用三 多项式的指数方程拟合,研究结果表明,LAI的增长过程呈S形,可分为3个时期,与群落中莎草类植物的物修划分相一致;6月至8月上旬LAI的增长速率较高,约持续70d,最大LAI为3.5左右;ULR与LAI的变化趋势相反,受值得 的共同影响,CGR在6月下旬最大;地上将初级生产量的增加在6月下旬最大,从5月中旬至7月下旬的80余天时间内,矮嵩草草甸可生产的肝上净生物量约占年地上总生物量的92.5%;生长季节内具有相对丰富的降雨和适宜的温度,是保证植物完成生长发育过程的有利因素。     

Carbon distribution of a well- and poorly-drained black spruce fire chronosequence

The objective of this study was to quantify carbon (C) distribution for boreal black spruce (Picea mariana (Mill.) BSP) stands comprising a fire chronosequence in northern Manitoba, Canada. The experimental design included seven well‐drained (dry) and seven poorly‐drained (wet) stands that burned between 1998 and 1850. Vegetation C pools (above‐ground + below‐ground) steadily increased from 1.3 to 83.3 t C ha^?1 for the dry chronosequence, and from 0.6 to 37.4 t C ha^?1 for the wet chronosequence. The detritus C pools (woody debris + forest floor) varied from 10.3 to 96.0 t C ha^?1 and from 12.6 to 77.4 t C ha^?1 for the dry and wet chronosequence, respectively. Overstorey biomass, mean annual biomass increment (MAI), woody debris mass, and litterfall were significantly greater (α = 0.05) for the dry stands than for the wet stands, but the bryophyte, understorey, and forest floor C pools were significantly less for the dry than for the wet stands. The root mass ratio decreased with stand age until 37 years after fire, was fairly constant thereafter, and was not significantly affected by soil drainage. The C pools of the overstorey and bryophyte tended to increase with stand age. Foliage biomass, litterfall, and MAI (for the dry stands) peaked at 71 years after fire and declined in the oldest stands. The results from this study illustrate that the effects of disturbance and edaphic conditions must be accounted for in boreal forest C inventories and C models. The appropriateness of using chronosequences to examine effects of wildfire on ecosystem C distribution is discussed.     

饲料中复方中草药对大菱鲆生长、饲料利用及非特异性免疫的影响

研究探讨了不同剂量的复方中草药[党参(Codonopsis pilosula Nannf.)、白术(Atractylodes macrocephala Koidz.)、茯苓(Poria cocos Wolf.)、熟地黄(Rehmannia glutinosa Libosch.)、甘草(Glycyrrhiza urale...     

The Glycoprotein Nature of Indoleacetic Acid Oxidase/Peroxidase Fractions and their Development in Pea Roots

IAA oxidase/peroxidase active fractions were separated using concanavalin A-sepharose into glycoprotein and non-glycoprotein fractions. No IAA oxidase peak was separable from peroxidase activity. The development of these fractions were followed in pea roots over a four day period. Initially the nonglycosylated IAA oxidase/peroxidase was the dominant fraction with the IAA oxidase/peroxidase ratio remaining close to unity. The glycosylated fraction developed later with IAA oxidase the dominant activity. Differential carbohydration of IAA oxidase/peroxidase fractions may determine the intracellular sites of activity of this molecular species.     

Effects of Small Water Stresses on Cell Turgor and Intercellular Space

A link was sought between small water stresses and the larger metabolic changes that accompany them. A simple infiltration weight method of measuring percentage intercellular space is described and its errors evaluated. It yielded values for leaves (16–35%) similar to those recorded elsewhere by the pycnometer method. The percentage of intercellular space decreased to 0–50% of the value in turgid leaves with a simultaneous loss of turgor only in the sunflower leaves. Turgor remained constant in the orange leaves. Similar results were obtained with the pycnometer method. Measurements revealed that the total or most of the decrease in the volume of sunflower leaves on loss of turgor was due to a decrease in area: the smaller decrease in the volume of orange leaves was entirely due to a decrease in thickness. It is suggested that the sclerophyll nature of the orange leaves is an adaptation to prevent a secondary O₂-deficit stress on exposure to a water stress.     

Evidence for a Protein Gel Structure Cross-linked by Metal Cations in the Intercellular Cement of Plant Tissue

The factors which modify the action of chelating agents in dissolvingthe intercellular cement in plant tissue have been investigated.The action was assessed by determining the degree of separationof cells in treated pea root tips. Greatly increased separation was observed when heavy metal chelatingagents were combined with EDTA (which, in addition to heavymetals, chelates Ca) indicating that two types of cations areinvolved in stabilizing the cement. After the cells had beenseparated by removal of the cations they could be recementedby treatment with divalent cations. In low concentrations onlycertain combinations of cations were effective, again pointingto the presence of more than one type of cation in the cement.Proteolytic enzymes or denaturing agents eliminated this capacityto recement. Pretreatment with divalent cations enhanced subsequentseparation (in EDTA solution). This effect could be counteredby treatment with monovalent cations. Pretreatment in buffers covering a wide range of pH resultedin increased separation both at pH 3 and at pH 11, suggestingan ampholytic component in the cement. Urea, when applied as a pretreatment, only enhanced separationwhen in high concentration. This effect was influenced by ionicstrength. When applied in combination with EDTA, urea producedan optimum effect at low concentration (0.125 M.). Pretreatmentin hot water also enhanced subsequent separation in EDTA solutions.High concentrations of KCl countered this effect. These findingspoint to the importance of H bonds in the intercellular cement.Thioglycollic acid, applied either as pretreatment or simultaneouslywith EDTA, lowered the EDTA concentration necessary to achieveseparation, suggesting the presence of S—S bridges. The curve relating the effect of pretreatment at varying temperatures,either in H₂O or in apolar solvents, to temperature, showeda sharp break, suggesting that the melting-point of an organizedgel might be involved. The conclusion is reached that the intercellular cement canbe regarded as an oriented gel structure containing proteinmolecules cross-linked by two types of metallic ion, the metalliccross linkage being chelate in character.