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1.
In this study, we evaluated the release of diclofop-methyl and triasulfuron from the roots of foliar-treated ryegrass and wheat. The study with 14C-diclofop-methyl indicated a basipetal translocation of foliar-applied herbicide in wheat and ryegrass. No root exudation from 14C-diclofop-methyl-treated wheat plants was observed, while 20 days after treatment (DAT) 0.2–0.9% of radioactivity absorbed by ryegrass was found exuded in the growing medium. Root exudation was stimulated three to six times by the presence of untreated wheat or ryegrass sharing the growing medium with diclofop-methyl-treated ryegrass. No subsequent uptake of exuded radiolabel by untreated plants (ryegrass or wheat) in the same pot with 14C-diclofop-methyl-treated ryegrass was observed. The study with 14C-triasulfuron indicated a basipetal translocation of foliar-applied herbicide in wheat and ryegrass and also into the growing medium. By 20 DAT, 0.5–4.2% of radioactivity absorbed by wheat or ryegrass was found exuded in the growing medium. The presence of untreated plants (wheat or ryegrass) in the same pot as triasulfuron-treated ryegrass or wheat induced exudation seven to 32 times more. The study also revealed a subsequent uptake of exuded compounds by untreated wheat or ryegrass sharing the medium of 14C-triasulfuron-treated plants. This study has demonstrated for the first time that the root exudation of exogenous compounds can be related to plant arrangement in pots. The implication is that herbicide root exudation and transfer, a form of allelopathy, could be significant in the field. A precise estimation of environmental fate, unexpected ecological side effects and residual activity of herbicides may require quantification of such exudation.  相似文献   

2.
The influence of non-ionic (X-77) and organosilicone (L-77) adjuvants and of methylated seed oil (MSO) on the uptake, translocation and efficacy of glyphosate was investigated in Bidens frondosa L. and Panicum maximum Jacq. In addition, the physicochemical properties of adjuvants and adjuvant + glyphosate aqueous solutions were determined. Significantly lower surface tension and contact angle values were obtained with aqueous solutions of L-77 alone and with glyphosate. Over a 48-h time course, it was observed that >50% of applied 14C-glyphosate was absorbed within 15 min in B. frondosa with L-77. At 6 h and thereafter, 14C glyphosate absorption was significantly higher with MSO compared with X-77 in B. frondosa . In P. maximum , uptake and translocation of 14C-glyphosate + adjuvant were increased in general up to 48 h after treatment application, except with L-77, which showed no improvement in uptake – instead there was a significant reduction compared with no treatment with L-77. This indicated its antagonistic effect on this grass species. The lower values of 14C-glyphosate in P. maximum also confirmed that adjuvant effects were species specific. In the efficacy studies, glyphosate formulated with L-77 achieved significantly higher control of B. frondosa , while there was no control of P. maximum with this treatment. This confirmed antagonism in glyphosate absorption into P. maximum by L-77. Furthermore, significantly higher control of tested plants was recorded with MSO in comparison to X-77, which confirms the solubilizing or humectant nature of MSO.  相似文献   

3.
Absorption and translocation of 14C-glyphosate was evaluated under controlled conditions in peas ( Pisum sativum L.) and broad beans ( Vicia faba L.) parasitised or not by crenate broomrape Orobanche crenata Forsk.). Absorption increased with time up to 12 days after treatment, and reached about 50% of the 14C-glyphosate applied. Three days after treatment 70–85% of the total herbicide absorbed had been translocated out of the treated leaflet. There was no consistent differ ence in absorption and translocation between infected and non-infected plants 12 days after treatment. The 14C-glyphosate concentration in the root system increased with time in broad beans. In peas it remained more or less constant from 3 days after treatment. Generally, pods were stronger sinks for glyphosate than other parts of the plant. Herbicide accumulation in broomrape increased with its growth stage, and the parasite was a much stronger sink for glyphosate than the legume root system.  相似文献   

4.
Rooted cuttings of Pyrus melanocarpa (Michx.) Willd. had a 3.5-fold greater tolerance to soil-applied hexazinone than those of Rubus hispidus L. in a greenhouse trial. R. hispidus accumulated four times more 14C-label in the foliage following root uptake of 14C-hexazinone than P. melano-carpa . Here, the greater uptake and susceptibility of R. hispidus was related to its greater root:fol-iage (weight) ratio compared to the tolerant P. melanocarpa . However, in whole plant metabolism studies employing younger plants there were no differences in 14C accumulation in the leaves. Here 14Chexazinone was converted to a number of hydroxylated and/or demethylated triazinone metabolites in both species following vacuum infiltration into leaf disks and root sections, or following root uptake in whole plants. A major difference in metabolism between the two species was the greater formation of the mono demethylated metabolite, B, [3-cyclohexyl-6-methylamino-l-methyl-l,3,5-triazine-2,4-dione] in P. melanocarpa which may also contribute to its greater tolerance. A loss of total 14Clabel from all plant parts with time may reflect cleavage of the 14C-ring-labelled herbicide.  相似文献   

5.
This study was conducted to determine the effects of three organosilicone-based and six conventional organic adjuvants on the absorption and translocation of 14C-glyphosate in guineagrass and redroot pigweed. The organosilicone adjuvants produced rapid absorption of the 14C-glyphosate into the redroot pigweed leaves, reaching maximum absorption within 0.5–1.0 h after application. The conventional adjuvants produced slower absorption of the 14C-glyphosate, as the maximum absorption was not achieved until at least 24 h after application in redroot pigweed, remaining similar until 72 h. In guineagrass, the maximum absorption of the glyphosate was earlier than 24 h with the organosilicone-based adjuvants, compared with longer times for the conventional adjuvants. The organosilicone-based adjuvants also increased the glyphosate translocation in redroot pigweed, but not in guineagrass. Organosilicone adjuvants have the potential to provide greater rainfastness to glyphosate on redroot pigweed and, to a lesser extent, on guineagrass.  相似文献   

6.
The effect of take-all root lesions on nitrate uptake of wheat was investigated in two experiments under controlled conditions. Plants were supplied with a nutrient solution labelled with 15N during stem elongation and flowering to assess the distribution of the isotopic tracer in the different plant organs, and particularly in root segments located on both sides of take-all lesions. The 15N atom percentage excess measured in root segments located below lesions longer than 1 cm was reduced on average by half compared with that in healthy roots and root segments above lesions, reflecting a reduction in nitrogen uptake by these root segments. This reduction probably resulted from the invasion and breakdown of phloem vessels by the fungus hyphae, interrupting energy supply and thus the uptake process. Severely infected plants showed an increase in the uptake rate per unit of efficient root, which appeared to be a compensatory response to reduction of efficient root biomass in order to satisfy shoot nitrogen demand. However, this compensatory response was insufficient to ensure nitrogen accumulation equivalent to that of healthy plants, as reductions in nitrogen accumulated in roots and aerial parts at flowering were up to 56 and 49%, respectively, for plants with more than 50% of the root system below lesions longer than 1 cm.  相似文献   

7.
The pattern of Cylindrocladium pteridis adhesion, germination and penetration in eucalypt leaves was assessed using scanning electron microscopy. The effects of inoculum concentration, leaf wetness period, plant age and branch position of cylindrocladium leaf blight and defoliation severity were assessed in greenhouse studies using two Eucalyptus grandis × E. urophylla hybrid clones. Penetration occurred through stomata, and there was no difference in the number of penetrations between young and old leaves. Percentage leaf area with lesions and defoliation increased with the increase in inoculum concentration (1 × 102 to 105 conidia mL−1), duration of leaf wetness period (6 to 48 h) and plant age (60 to 180 days). Branch position in plants also significantly affected the percentage leaf area with lesions and defoliation, the latter variable being significantly higher at the stem base. The highest values of lesion area were also observed on leaves at the stem base in both clones. The Pearson correlation between defoliation and leaf area with lesions was significant in all experiments ( r  > 0·9) indicating a high association between these two variables.  相似文献   

8.
Summary. White ash ( Fraxinus americana L. ) trees, 2 years of age, treated continuously with 10 ppm picloram (4-amino-3,5,6-trichloropicolinic acid) in nutrient culture were only slightly injured after 4 weeks whereas red maple ( Acer rubrum L.) trees were killed after only 2 weeks treatment.
When the roots were exposed to 10 ppm 14C-picloram, the rate of root uptake, acropetal translocation in the stem, and accumulation in the leaves was much lower in the susceptible red maple than in the tolerant white ash. The foliar penetration and translocation of 14C-picloram applied to the leaves was very slight but similar in both species. Although a radiolabelled picloram metabolite was isolated from plant extracts, it was formed at equal rates in both species.
It was concluded that the tolerance of white ash was not related to lower rates of picloram uptake or faster rates of picloram detoxication. It was postulated that the high susceptibility of red maple was due to a blockage of the xylem by picloram which caused death by a dessication of the leaves and upper stems.
Action sélective du piclorame sur Fraxinus amerieana L. et Acer rubrum L.  相似文献   

9.
The transport and differential phytotoxicity of glyphosate was investigated in maize seedlings following application of the herbicide to either roots or shoots. One-leaf maize seedlings (Zea mays L.) were maintained in graduated cylinders (250 mL) containing nutrient solution. Half of the test plants were placed in cylinders (100 mL) containing different 14C-glyphosate concentrations; the remainder received foliar appliation of 14C-glyphosate. After 26 h, the roots and the treated leaves were washed with distilled water, and the plants placed again in cylinders (250 mL) containing fresh nutrient solution for 5 days. Plants were weighed, and split into root, seed, cotyledon, coleoptile, mesocotyl, first leaf and apex. The recovery of 14C-glyphosate was over 86%. For both application treatments, the shoot apex was the major sink of the mobilized glyphosate (47.9 ± 2.93% for root absorption and 45.8 ± 2.91% for foliar absorption). Expressed on a tissue fresh weight basis, approximately 0.26 μg a.e. g−1 of glyphosate in the apex produced a 50% reduction of plant fresh weight (ED50) when the herbicide was applied to the root. However, the ED50 following foliar absorption was only 0.042 μg a.e. g−1 in the apex, thus maize seedlings were much more sensitive to foliar application of the herbicide.  相似文献   

10.
Summary. Previous findings suggested that the translocation in Agropyron repens of 2,2-dichloropropionic acid (dalapon) may be considerably affected by the transpiration rate. This relationship has been studied further in the present investigation using 14C-labelled material and autoradiography.
It was found that when dalapon was applied to the leaves and the treated plants were placed in darkness a reduction in the transpiration rate of ca. 90% was associated with a marked increase in the amount of dalapon translocation into the roots and tillers. The evidence provided by the autoradiographs was confirmed by a quantitative assay of the 14C present in the roots. It was also found, however, that translocation was not appreciably affected either by a 50% reduction in the light intensity or when the transpiration rate was reduced by placing the plaints under conditions of high humidity in the light or by the application of white petroleum jelly to the leaves. An alternative hypothesis, namely that the effect of darkness on the movement of the herbicide might be due to changes induced in the normal pattern of assimilate translocation was also investigated but was not supported by the results obtained. Further experimentss, in which various parts of the treated shoot were placed in the dark, suggested that the effect of darkness on the translocation of dalapon is exerted primarily on the treated leaf itself.
Etudes sur to migration dans Agropyron repens de l'acide 2,2-dichloropropionique marqué avec 14C  相似文献   

11.
Summary. Plants of Potamogeton nodosus, a submersed aquatic, were treated with the di-sodium salt of 7-oxabicyclo(2,2,l)heptane-2,3-dicarboxylic acid-14C (endothal-14C). Gross radioautographs showed that the 14C label moved from mature photosynthesizing leaves and accumulated in the apices and developing secondary plants. Similar results were obtained with mid-leaf, stem (internode) and winter-bud applications. No move-ment of radioactivity occurred following root treatment. The results indicate symplastic translocation of endothal-14C when applied to the leaf, stem or winter bud. It is suggested that endothal can cause the death of plants by direct injury to root tissues subsequent to absorption.
Recherches sur la migration de l'endothal-14C dans le Potamogeton nodosus Poir.  相似文献   

12.
Methods to assess light leaf spot ( Pyrenopeziza brassicae ) on winter oilseed rape cultivars were compared in laboratory, controlled-environment and field experiments. In controlled-environment experiments with seedling leaves inoculated at GS 1,4, the greatest differences in percentage area affected by P. brassicae sporulation were observed with inoculum concentrations of 4 × 103 or 4 × 104 spores mL−1, rather than 4 × 102 or 4 × 105 spores mL−1, but older leaves had begun to senesce before assessment, particularly where they were severely affected by P. brassicae . In winter oilseed rape field experiments, a severe light leaf spot epidemic developed in 2002/03 (inoculated, September/October rainfall 127·2 mm) but not in 2003/04 (uninoculated, September/October rainfall 40·7 mm). In-plot assessments discriminated between cultivars best in February/March in 2003 and June in 2004, but sometimes failed to detect plots with many infected plants (e.g. March/April 2004). Ranking of cultivar resistance differed between seedling experiments done under controlled-environment conditions and field experiments. The sensitivity of detection of P. brassicae DNA extracted from culture was greater using the PCR primer pair PbITSF/PbITSR than using primers Pb1/Pb2. P. brassicae was detected by PCR (PbITS primers) in leaves from controlled-environment experiments immediately and up to 14 days after inoculation, and in leaves sampled from field experiments 2 months before detection by visual assessment.  相似文献   

13.
Field resistance of Echinochloa spp. to propanil has been previously reported in Costa Rica, Colombia and Arkansas (USA). In this study, the mechanism of resistance was investigated in three resistant (R) and three susceptible (S) biotypes. The shoot fresh weight reduction in pot-grown plants from a post-emergence spray of propanil at 2.44 kg a.i. ha−1 on biotypes R/S from Costa Rica, Colombia and Arkansas was 35/98%, 25/79% and 20/82% respectively. In vitro chlorophyll fluorescence data from leaf tissue incubated in propanil showed that photosynthesis was inhibited in all biotypes, indicating that the propanil-binding site and enzyme were not altered. After transfer to herbicide-free solution, photosynthesis recovered only in resistant biotypes, indicating that the mechanism of resistance was caused by enhanced metabolism of the herbicide. Simultaneous treatment with fenitrothion, an aryl acylamidase inhibitor, prevented the recovery of photosynthesis in leaf tissue in two resistant biotypes. In contrast, the cytochrome P450 mono-oxygenase inhibitor, 1-aminobenzotriazole, did not prevent recovery from propanil in leaf tissue. Application of 14C-propanil to the second leaf of intact Echinochloa plants showed that c . 90% of the radioactivity remained in the treated leaf for up to 72 h after application. No major differences in translocation between R and S biotype plants were found. TLC analysis of tissue extracts from the treated leaves showed substantially less radioactivity associated with propanil, present after 72 h in rice or in the three R biotypes, compared with S biotypes.  相似文献   

14.
Summary. A method of exposing seedlings of Norway spruce (Picea abies (L.) Karst.) to 14CO2 is described. Within the 1st hr alter 14CO2 exposure, no translocation of the 14C out of the treated branch could be observed. After a 24-hr period, however, the 14C in dormant seedlings had been translocated basipetally to part of the root system only, with no lateral diffusion of the 14C-compounds in the stem. About a week after exposure, both symplastic and apoplastic patterns of translocation had caused a more uniform distribution of 14C. In seedlings at active internode elongation, the translocation patterns were fundamentally identical to those in dormant seedlings, but the active shoot growth had led to a more uniform distribution of the 14C.
Simazine at 20 ppm had apparently stimulated both the photofixation of 14CO2 and the rate of translocation of the 14C-assimilates. At 30 ppm, however, simazine had blocked the translocation of nutrients to the roots. On the other hand, the 14CO2 uptake was not influenced. The simazine incubation had apparently no influence on the synthesis of cationic photosynthate.  相似文献   

15.
The efficacy of the commercial glyphosate [( N -phosphonomethyl) glycine] formulations Roundup Ultra, Touchdown and Engame were compared for the control of prickly sida ( Sida spinosa L.), morningglory ( Ipomeae hederacea var. integriuscula Gray), sicklepod ( Senna obtusifolia L.) and purple nutsedge ( Cyperus rotundus L.). Engame is a new formulation of glyphosate that contains glyphosate acid and 1-aminomethanamide dihydrogen tetraoxosulfate (AMADS), a proprietary mixture of sulfuric acid and urea, other than glyphosate salt and surfactants. Injury by Engame differed from Roundup Ultra and Touchdown in that necrotic lesions formed on leaves several hours after treatment. Leaves of very susceptible species, such as prickly sida, were rapidly, although incompletely, desiccated and then became chlorotic and died in a manner typical of other glyphosate formulations. Engame was 2–3 times more active to growth inhibition than either the Roundup Ultra or Touchdown formulations, based on GR50 comparisons expressed on an acid equivalent basis. The GR50 estimates did not change over the 3 week evaluation period for prickly sida and purple nutsedge, and after 2 weeks after treatment for morningglory. The GR50 estimates for sicklepod decreased over the 3 week evaluation period indicating a slower response to glyphosate. The application of AMADS alone caused minute necrotic lesions on sicklepod and purple nutsedge, and lesions up to 3 mm in diameter on prickly sida and morningglory. Further injury from AMADS was not noted and plants resumed growth without apparent delay. At glyphosate rates above 1120 g ha−1, greater than 80% control was achieved at 7 days after treatment. These results demonstrate that glyphosate efficacy can be further enhanced by formulations that apparently improve uptake and translocation.  相似文献   

16.
Uptake of [14C-phenyl]2,4-D-butyl by 4- to 6-week-old tomato plants was measured for vapour concentrations in the range 0.3–19 ng litre?1, for an exposure period of 4 h. Calculation of boundary layer thicknesses at the surface of the leaves, and depletion of the vapour concentration due to uptake by the plants, suggested that the plants experienced concentrations very close to the nominal values. Relationships between external vapour concentration and plant uptake, expressed in terms of fresh weight, leaf area, or on a whole plant basis, were linear in all cases. Twenty-four hours after the commencement of exposure, leaves contained 63–93% of the total herbicide in the plant; the proportion retained by the leaves was greater at low vapour concentrations. The largest amount of herbicide was present in leaves from the mid-position on the stem, but in terms of leaf area, the amount was greatest in leaves at the apex and decreased basipetally. It is not known whether this was due to a greater uptake rate per leaf area at the apex, or to translocation. As visible symptoms of phytotoxicity usually develop at the apex, both of these processes, together with the preferential retention of herbicide in leaves at low vapour concentrations, may all contribute to the development of vapour damage.  相似文献   

17.
First leaves of barley seedlings grown in solution culture were inoculated with powdery mildew when the second leaf was fully emerged. 14C-labelled carbon dioxide was fed to either first or second leaves of infected and non-infected plants. Translocation of labelled photoassimilates into roots, and partitioning into soluble, storage and structural fractions were studied in tip, mid and basal regions of primary roots 24 h after feeding. Mildew reduced the total activity in the plant, but had little effect on assimilate distribution since the percentage activity translocated to roots was only transiently reduced, approximately 7 days after infection. Reduced import led to a reduction in the specific activity of different fractions within roots, reductions being greatest in root tips. These changes were similar whichever leaf was fed. Changes in specific activity became progressively more pronounced in the 10 days following infection, and were paralleled by a reduction in the mitotic index of root tips. It is concluded that meristematic activity, and thus the growth, of primary roots of barley is particularly sensitive to reductions in photoassimilation caused by powdery mildew infection.  相似文献   

18.
The potential of three externally applied chemical plant activators, Bion, BABA and methyl jasmonate, known to act only through the plant defence system and not on the pathogen directly, to induce resistance against wild-type Pectobacterium carotovorum was examined in white-flowered calla lily ( Zantedeschia aethiopica ). Following a 24-h induction period, plants were challenge-inoculated with P. carotovorum , originally isolated from calla lily or potato plants, previously transformed using a gfp broad-host-range promoter-probe vector. After another 24 h, Bion treatment (10  µ g mL−1, as a drench) reduced disease symptoms more than sixfold and bacterial proliferation by four orders of magnitude. BABA treatment (5–10  µ g mL−1, also as a drench) reduced the rate of infection by 75–85%. However, the protection afforded by both inducers did not persist. Also, at higher concentrations both displayed a phytotoxic effect. By contrast, methyl jasmonate (10 m m , applied as a leaf spray) completely inhibited P. carotovorum development in calla lily leaves and afforded a long-lasting effect. It is suggested that the defence response of calla lily against P. carotovorum involves the SA-signalling pathway in the short term, but the jasmonate/ethylene-signalling pathway is required for durable protection.  相似文献   

19.
The effect of wind on the dispersal of oospores of Peronosclerospora sorghi , cause of sorghum downy mildew (SDM) is described. The oospores are produced within the leaves of aging, systemically infected sorghum plants. These leaves typically undergo shredding, releasing oospores into the air. Oospores are produced in large numbers (6.1 × 103 cm−2 of systemically infected leaf) and an estimate of the settling velocity of single oospores (0.0437 m s−1) of P. sorghi indicated their suitability for wind dispersal. In wind tunnel studies wind speeds as low as 2 m s−1 dispersed up to 665 oospores per m3 air from a group of leaves previously exposed to wind and displaying symptoms of leaf shredding. The number of oospores dispersed increased exponentially with increasing wind speed. At 6 m s−1, up to 12 890 oospores per m3 air were dispersed. Gusts increased oospore dispersal. A constant wind speed of 3 m s−1 dispersed a mean of 416 oospores per m3. When gusts were applied the mean was 15 592 oospores per m3. In field experiments in Zimbabwe, oospores were sampled downwind from infected plants in the field and at a height of 3.8 m above ground level immediately downwind of an infected crop. These data indicate that wind could play a major role in the dispersal of oospores from infected plants in areas where SDM infects sorghum, perhaps dispersing oospores over long distances.  相似文献   

20.
It has long been known that calcium ion antagonizes glyphosate, but it was not clear whether the stoichiometry of their interaction is 1:1 or 1:2. Two independent methods were used to determine which stoichiometry was the most probable. First, dose–response curves of barley ( Hordeum vulgare L.) plants treated with glyphosate were determined in the presence of 0, 1.25, 2.5, 5 and 10 mM CaCl2. The doses of 'free' glyphosate (=not inactivated by calcium ion) were computed using the assumptions of 1:1 and 1:2 stoechiometries. The response curves were redrawn as a function of 'free' glyphosate. Analysis showed that the 1:2 hypothesis could be rejected, whereas the 1:1 hypothesis was highly probable. Second, kinetics of glyphosate penetration into barley leaves were determined in the presence of 0, 2.5 and 10 mM CaCl2. The concentrations of 'free' glyphosate were computed as above. The kinetics of glyphosate penetration at these concentrations were established and were compared to the kinetics of glyphosate penetration in the presence of CaCl2. Again, the 1:2 hypothesis was rejected, whereas the 1:1 hypothesis was more probable. These results strongly suggest that the stoichiometry of the Ca2+:glyphosate association is 1:1 in deposit residuals on the leaf surface.  相似文献   

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