Investigations into the movement of glyphosate from treated to adjacent untreated plants

Transfer of glyphosate from treated to adjacent untreated plants was investigated under glasshouse conditions using wheat and Agropyron repens. When glyphosate was used at concentrations characteristic of conventional field application rates, and where shoot contact was prevented, no symptoms were observed on untreated plants. When there was shoot contact, and when glyphosate was used at 2 kg a. i./ha (10 g a. i./litre), phytotoxic effects were observed on untreated plants. At higher concentrations of glyphosate (90 or 180 g a. i./litre), typical of selective applications with ropewick or roller applicators, evidence of root transfer of herbicide was found. In pot experiments these phytotoxic effects were variable, due, perhaps, to variable amounts of root contact. Confining the roots, by growing the plants in tubes, increased the level of phytotoxicity.     

RNA silencing movement in plants

Higher eukaryotes have developed a mechanism of sequence-specific RNA degradation which is known as RNA silencing. In plants and some animals, similar to the nematode Caenorhabditis elegans, RNA silencing is a non-cell-autonomous event. Hence, silencing initiation in one or a few cells leads progressively to the sequence-specific suppression of homologous sequences in neighbouring cells in an RNA-mediated fashion. Spreading of silencing in plants occurs through plasmodesmata and results from a cell-to-cell movement of a short-range silencing signal, most probably 21-nt siRNAs (short interfering RNAs) that are produced by one of the plant Dicer enzymes. In addition, silencing spreads systemically through the phloem system of the plants, which also translocates metabolites from source to sink tissues. Unlike the short-range silencing signal, there is little known about the mediators of systemic silencing. Recent studies have revealed various and sometimes surprising genetic elements of the short-range silencing spread pathway, elucidating several aspects of the processes involved. In this review we attempt to clarify commonalities and differences between the individual silencing pathways of RNA silencing spread in plants.     

RNA silencing movement in plants

Multicellular organisms, like higher plants, need to coordinate their growth and development and to cope with environmental cues. To achieve this, various signal molecules are transported between neighboring cells and distant organs to control the fate of the recipient cells and organs. RNA silencing produces cell non-autonomous signal molecules that can move over short or long distances leading to the sequence specific silencing of a target gene in a well defined area of cells or throughout the entire plant,respectively. The nature of these signal molecules, the route of silencing spread, and the genes involved in their production, movement and reception are discussed in this review. Additionally, a short section on features of silencing spread in animal models is presented at the end of this review.     

Long-distance movement of viruses in plants

During systemic infections, plant viruses move long distances through the plant vasculature. Leaf age, the rate of plant development, plant anatomy and the direction of nutrient flow in the vasculature influence the pattern and extent of systemic spread of the virus, and, in turn, these factors are major determinants of virus resistance.     

RNA silencing movement in plants.

Higher eukaryotes have developed a mechanism of sequence-specific RNA degradation which is known as RNA silencing. In plants and some animals, similar to the nematode Caenorhabditis elegans, RNA silencing is a non-cell-autonomous event. Hence, silencing initiation in one or a few cells leads progressively to the sequence-specific suppression of homologous sequences in neighbouring cells in an RNA-mediated fashion. Spreading of silencing in plants occurs through plasmodesmata and results from a cell-to-cell movement of a short-range silencing signal, most probably 21-nt siRNAs (short interfering RNAs) that are produced by one of the plant Dicer enzymes. In addition, silencing spreads systemically through the phloem system of the plants, which also translocates metabolites from source to sink tissues. Unlike the short-range silencing signal, there is little known about the mediators of systemic silencing. Recent studies have revealed various and sometimes surprising genetic elements of the short-range silencing spread pathway, elucidating several aspects of the processes involved. In this review we attempt to clarify commonalities and differences between the individual silencing pathways of RNA silencing spread in plants.     

Nitrate movement in xylem of lucerne plants

Nitrate content in lucerne stems and leaf blades immersed by cut ends in distilled water or in KNO₃ solution increased with the increase in KNO₃ concentration and with the duration of exposure under irradiance of 100 or 230 W m^?2 PAR. The nitrate content increased from basal stem parts to apical stem parts and leaves. Nitrate was transported mainly with transpiration stream. Some flow variations occurred in stems causing time changes in nitrate content in different parts of stems.     

植物转基因方法概述

综述了植物基因转化的不同方法。植物基因转化方法主要包括直接基因转移和农杆菌介导的转化,直接基因转移又包括PEG介导、电激介导和基因枪方法。相比之下,农杆菌转化方法具有明显的优势;本文对其方法和机制作了较为全面的介绍。     

The movement of amino acids into rabbit oviductal fluid.

Twenty-three amino acids appeared linearly in oviduct fluid to reach an average concentration 27% of that in the plasma, with glycine and alanine present in greatest amount. In contrast, the concentration of urea in the fluid approached its plasma concentration after 1 h, and remained at this level for the duration of the experiment. The oviduct was unable to bring the overall uphill transport of amino acids from plasma to oviduct lumen. The amounts of amino acids appearing in the oviduct lumen of rabbits injected 3 days previously with hCG were mostly similar to those of the controls, but the movements of 6 neutral amino acids appeared to be enhanced relative to their plasma concentrations following ovulation.     

亚洲柑桔木虱若虫在寄主上的转移和扩散研究

黄龙病是世界柑桔产业的一种毁灭性病害，亚洲柑桔木虱Diaphorina citri Kuwayama为黄龙病亚洲种和美洲种的媒介昆虫，其成虫和高龄若虫都能传病。本文研究亚洲柑桔木虱若虫在感染黄龙病及健康寄主上的转移和扩散规律，发现3龄及3龄以上若虫在柑桔植株垂直和水平位置的嫩梢之间转移现象十分明显，但在黄龙病植株上转移速度较健康植株慢，且嫩梢间的转移速度受虫密度的影响，密度越高转移速度越快。在有选择的条件下，水平位置转移过程中若虫更趋向黄龙病植株。此外，在健康寄主上的木虱若虫有明显向植株下部转移的现象，向下部转移的若虫个体数显著高于黄龙病寄主。本文明确了木虱若虫的扩散规律和寄主感染黄龙病对其转移和扩散产生的影响，为柑桔木虱和黄龙病防治提供参考。     

The movement of tobacco mosaic viruses and potato virus X through tomato plants

Tomato aucuba mosaic virus, tobacco mosaic virus and potato virus X took 3'5-4, 5 and 3 days respectively to move from inoculated tomato leaflets into the petioles and stems
On reaching the stem each virus usually first moved downward, but in some plants both upward and downward movement occurred simultaneously and in a few
upward movement occurred first.
All three viruses travelled through the stem at approximately the same rate. Each was capable of travelling more than 80 cm. during the first 12 hr. after entering the stem, giving a minimal average rate of about 8 cm. per hr.
Uninfected pieces of stem invariably occurred between infected pieces. Maximum lengths of stem through which virus particles had apparently passed without causing infection, were 44.5, 49 and 39 cm. for the three viruses.     

The distribution and movement of apterous Myzus persicae on rapidly growing turnip plants

Abstract. 1. The spatial distribution of both adult apterous and nymphal M.persicae was related to the "age" of the leaf.
2. This distribution was bimodal and was maintained even on rapidly "ageing" leaves by frequent emigration.
3. The spatial distribution was also found to change between regions of a leaf, the densest populations occurring at the base of all leaves, but with the populations most evenly distributed on the young and old leaves.
4. The spatial distribution also changed during the nymphal period, the youngest nymphs being found predominantly on the lamina, the fourth instar and adults on the largest available veins.
5. On rapidly growing plants, individual M.persicae may move to a new feeding site as frequently as every 24–48 h.
6. Some of the causes and consequences of this frequent dispersal are discussed.     

Use of transgenic plants to measure insect herbivore movement

Use of ingested transgenic corn tissue as a marker for measuring movement of adult Diabrotica virgifera virgifera (LeConte) (Coleoptera: Chrysomelidae; western corn rootworm) was investigated. Laboratory observations of beetles feeding on corn foliage, pollen, silks, or soybean foliage provided background on feeding patterns. The interval between food consumption and its appearance in feces (gut passage time) ranged from 102.7 +/- 11 min for soybean foliage to 56.7 +/- 2.9 min for corn silks. In a laboratory assay, protein expression tests identified the presence of Cry3Bb1 protein inside 50% of adult D. virgifera for up to 16 h after they had last consumed Cry3Bb1 protein-expressing corn silks from 'YieldGard Rootworm' corn plants (Monsanto Co.). Cry3Bb1 protein could not be detected by 32 h postfeeding. The proportion of Cry3Bb1 protein-positive beetles declined linearly with increasing time since feeding on 'YieldGard Rootworm' tissue. Approximately 20% of adult D. virgifera collected near 'YieldGard Rootworm' corn plots tested positive for Cry3Bb1 protein, indicating 'YieldGard Rootworm' tissue consumption within the last 16-32 h. Based on a 16- to 32-h postfeeding detection interval for Cry3Bb1 protein and the distance between 'YieldGard Rootworm' sources and sites where Cry3Bb1-positive insects were collected, 85.3% of males and females moved < or = 4.6-9.1 m/d through R2-R3 stage corn. Among Cry3Bb1-positive adults that left corn and were captured in an adjacent soybean field, 86.4% of males and 93.1% of females moved < or = 4.6-9.1 m/d through soybean. Detection of transgenic plant tissues in mobile insect herbivores is a novel application of biotechnology to the study of insect movement.     

The movement of sulfate and thiosulfate into in vivo choroid plexus

The accumulation of sulfate (SO₄?) and thiosulfate (S₂O₃?) in the choroid plexus, brain, and cerebrospinal fluid (CSF) of the rat was measured at various plasma levels of these anions. Increasing the plasma SO₄ ? or S₂O₃ ? concentration levels 40- and 580-fold, respectively, resulted in a linear increase in CSF, brain and choroid plexus concentration of these ions. The relationship between the concentration of these ions in CSF and choroid plexus was also approximately linear over a wide CSF concentration range. In addition, S₂O₃? did not appear to influence the relation between the concentration of SO₄? in choroid plexus and CSF. The results seem to indicate that there is no saturation of the mechanism responsible for maintaining the low SO₄? or S₂O₃? concentration in CSF nor does there appear to be competition between these anions for clearance from the CSF. These findings are in conflict with data supporting the active transport of SO₄? and S₂O₃? from the CSF across the CSF-blood barrier (choroid plexus).