大豆根瘤侵染细胞中一种细胞质内含物的电镜观察

在中国丰收11号大豆根瘤侵染细胞中,我们发现了一种电子密度很高,体积很大,形状为圆形或近似圆形,外面没有界膜,常位于胞间隙附近的特殊的细胞质内含物。高尔基体及其小泡,丰富的粗糙型内质网和核糖体常在它的附近,其中一些核糖体正沉积在它的表面。它主要是由核糖体凝聚而成,高尔基体和内质网在它的形成中也起了一定作用。它的内部含有颗粒状,纤维状,泡状和管状物质。它的出现似乎与侵染细胞固氮有关。     

Vegetative reproduction of trees in some European natural forests

Various means of vegetative reproduction in unexploited forests in western Europe are illustrated with examples. Root suckers are sometimes almost the only method of forest regeneration near the limits of tree growth on the Wadden islands and they can play an important role in forest gaps and riverine forests. Trunk suckers finally replacing their parent trees occur in Alnus, Tilia and Ulmus. Partial uprooting of trees, favoured by special soil conditions, was shown to be an important condition for vegetative reproduction. Temporary survival after uprooting gives opportunity for development of reiterative sprouts, that can replace the vertical axis of a fallen tree. Contact of living branches or even whole stems with soil or mouldering logs favours the growth of adventitious roots. Thus vegetatively reproduced individual trees establish before the uprooted parent tree finally dies. Examples of the clonal spreading of trees are given and a special strategy of layering its branches in pasture woods has been described for beech. Modern forestry rigorously eliminates conditions suitable for the vegetative reproduction of forest trees so their abilities in this respect are often underestimated. Vegetative reproduction seems to be particularly important under circumstances where natural growth is difficult e.g. near the limits of tree growth, on dynamic sites and under heavy shade.     

表面活性剂和Ca~(++)对大麦根质膜透性的作用

阳离子型表面活性剂(CTMA)以低于CMC的浓度、非离子型表面活性剂(Triton-X-100)以高于CMC的浓度引起大麦离体根K~+及可溶性糖的外流,并有浓度效应。5℃时表面活性剂引起溶质外流,CTMA预处理10 min后,Ca~(++)无抑制作用。Ca~(++)与 Triton-X-100同时处理大麦根促进溶质外流。Mg~(++)、Mn~(++)对CTMA及Triton-X-100引起溶质外流的效应与Ca~(++)的相类似,但不如Ca~(++)有效。     

Restitution of polarity in statocytes from centrifuged roots*

Abstract The structural polarity of statocytes from cress roots is changed by centrifugation. Upon low- dose centrifugation (3000 g min), the extent of stratification depends on statocyte position, i.e., central statocytes are affected more than lateral ones. Upon higher doses of centrifugation (60,000 and 360,000 g min), a uniform density gradient is established in all statocytes. If, after centrifugation, the roots are exposed to gravity again, the endoplasmic reticulum (ER) cisternae are relocated parallel to the periclinal cell walls within a few minutes; this relocation is independent of the direction of gravity in relation to the root axis, and independent of the previously applied centrifugation dose. This supports the notion that polarity is determined genetically. Cytochalasin B treatment, before and during centrifugation, totally inhibits the relocation of ER. After removing the drug by rinsing the roots, the statocytes restore cell polarity and relocate ER. These results indicate that relocation of ER cisternae may be mediated by microfilaments. When centrifuged roots are exposed to 1 g in the horizontal position, the latent period of gravitropism increases by 8–10 min relative to controls, regardless of the previously applied centrifugation doses. The kinetics of curvature are virtually identical. Since the increase in the latent period coincides with the time needed for most statocytes to restore the distal cell pole, it is evident that perception of gravity is correlated to the integrity of the distal cell pole.     

Local population differences in emergence of cabbage root flies from south-west Lancashire: implications for pest forecasting and population divergence

ABSTRACT.

• 1 Emergence of cabbage root fly, Delia radicum (L.), from overwintering populations of puparia collected from twenty-one sites in south-west Lancashire, was extremely variable.
• 2 The patterns of emergence indicated that there were two extreme biotypes, one with early- and the other with late-emerging flies. There was also evidence of an intermediate biotype, tending more to early than to late emergence.
• 3 This gradient of biotypes, or clinal divergence, was maintained by populations breeding at different times and by females mating close to their sites of emergence. Non-dispersive females then perpetuated their genotype within their own locality.
• 4 The time of emergence was not obviously associated with the type of host-crop on which larvae had developed.
• 5 The late-emerging biotype was most prevalent around Halsall. The minimum distance between populations of the late- and the early-emerging biotypes was 16 km. 20 km south-east from Halsall only half of the fly population was early-emerging, possibly a result of a displacement of the Halsall biotype by the prevailing NW wind.
• 6 Regional-based forecasts will need to take into account the emergence characteristics of the populations to predict the peak periods of cabbage root fly activity adequately in south-west Lancashire and other areas where emergence patterns differ.

     

Correlation between infection by Rhizobium leguminosarum and lectin on the surface of Pisum sativum L. roots

The lectin on the surface of 4- and 5-dold pea roots was located by the use of indirect immunofluorescence. Specific antibodies raised in rabbits against pea seed isolectin 2, which crossreact with root lectins, were used as primary immunoglobulins and were visualized with fluorescein- or tetramethylrhodamine-isothiocyanate-labeled goat antirabbit immunoglobulin G. Lectin was observed on the tips of newly formed, growing root hairs and on epidermal cells located just below the young hairs. On both types of cells, lectin was concentrated in dense small patches rather than uniformly distributed. Lectin-positive young hairs were grouped opposite the (proto)xylematic poles. Older but still-elongating root hairs presented only traces of lectin or none at all. A similar pattern of distribution was found in different pea cultivars, as well as in a supernodulating and a non-nodulating pea mutant. Growth in a nitrate concentration which inhibits nodulation did not affect lectin distribution on the surface of pea roots of this age. We tested whether or not the root zones where lectin was observed were susceptible to infection by Rhizobium leguminosarum. When low inoculum doses (consisting of less than 10⁶ bacteria·ml^-1) were placed next to lectin-positive epidermal cells and on newly formed root hairs, nodules on the primary roots were formed in 73% and 90% of the plants, respectively. Only a few plants showed primary root nodulation when the inoculum was placed on the root zone where lectin was scarce or absent. These results show that lectin is present at those sites on the pea root that are susceptible to infection by the bacterial symbiont.Abbreviations FITC fluorescein isothiocyanate - TRIC tetramethylrhodamine isothiocyanate     

Completion of diapause in field populations of the cabbage root fly (Delia radicum)

The various diapause and post-diapause stages entered by cabbage root fly pupae during the overwintering period are shown schematically. Although diapause induction started in mid-Aug., the early-pupating insects did not develop further but were maintained in diapause by the warm autumn temperatures. Therefore, diapause development was simultaneous in all Wellesbourne pupae, whether of second or third generation origin. Diapause development started only in mid-Oct., when mean soil temperatures fell below 10°. In the field, 90% of the overwintering population of cabbage root fly pupae had completed pleted diapause by 5 March 1980, 17 Feb. 1981 and 18 Feb. 1982. This was equivalent to a duration of 19 weeks from mid-Oct. onwards, during the winters of 1979–80, 1980–81 and 1981–82 respectively. A further break between the completion of diapause and the warm conditions required to start post-diapause development also helps to condense the emergence of flies in the spring. Hence, an accurate forecast of the time of spring attack by populations of flies similar to those at Wellesbourne should be possible.This study was financed partly by the Commission of the European Communities as CEC Contract No. 0771.     

Trichinella spiralis: selective intestinal immune deviation in the rat

In rats, infections with 100-2000 Trichinella spiralis muscle larvae lead to a prompt immunity that is expressed in parasite expulsion within 14 days. Rats infected with more than 2000 larvae display impaired immunity with rejection delayed by 50% (7 days) or more. Suppression is selective for expulsive immunity as the antifecundity response of rats is directly proportional to dose and is expressed sooner in heavily infected subjects. Suppression of intestinal expulsive immunity was suggested by the fact that, with low doses (2000 larvae or less), worm rejection was inhibited by cortisone, whereas cortisone inhibited antifecundity but had no discernable effect on worm rejection in high-dose infections. Evidence for local immune deviation as opposed to systemic immunosuppression was obtained in experiments using parabiotic rats. When one partner was infected with 6000 worms and the other with 200, the rat infected with 200 parasites showed earlier rejection than was seen in single controls infected with 200 worms. The prolonged survival of high-dose adults was not accompanied by a change in the site of worm residence in the gut. Immunological parameters such as serum antibody levels, the number of activated cells or specific anti-T. spiralis lymphocytes in thoracic duct lymph were all increased in a dose-dependent manner. These experiments therefore demonstrate a novel autoprotective mechanism by which adult T. spiralis selectively reduce the expression of expulsive immunity in the gut.     

Isolation of a brain peptide identical to the intestinal PHI (peptide HI)

The isolation of a brain peptide identical to the intestinal peptide PHI (peptide HI) is described. The peptide was isolated from porcine brain extract using a chemical assay method based on its C-terminal isoleucine amide structure. The complete amino acid sequence of the peptide was found to be: His-Ala-Asp-Gly-Val-Phe-Thr-Ser-Asp-Phe-Ser-Arg-Leu-Leu-Gly-Gln-Leu-Ser-Ala- Lys-Lys-Tyr-Leu-Glu-Ser-Leu-Ile-NH2. This sequence is identical to the intestinal peptide thus demonstrating PHI to be a brain-gut peptide. The role of PHI in the central nervous system as a neurotransmitter or neuromodulator is discussed.