首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Studies were made of seedling emergence of three phenotypes of Avena fatua L. with dif ferent coloured lemmas (fA, fB, fC) originally collected from one site. Each phenotype was grown under the same conditions in 1975 and the resulting seed buried 25 mm deep in soil im mediately after collection. The soil was either left uncultivated (all phenotypes) or cultivated monthly (phenotype fA only). Seedling emergence was assessed weekly and the number of remaining viable seeds was determined at the end of three years. Seeds of different lines of A. fatua (fA phenotypes) obtained from separate locations were grown under the same conditions in 1983, buried and seedling emergence moni tored for 85 months. Without cultivation, overall emergence (mean of three phenotypes) in successive autumns and springs was 9%, 18%, 9%, 33%, < 1%, 14% and <1%. A further 3% of viable seeds were recovered at the end of the experiment. Periodicity of emergence was the same for all phenotypes. Actual numbers of seedlings emerging in each of the periods varied between phenotypes. Total emergence of seed from the inner zone of panicles was significantly less than that from the outer zone, although there was little difference between the two zones in each of the natural emergence periods. Cultivation increased emergence, particularly from secondary seed in the first spring after burial, but did not changes its periodicity. By the second spring seed numbers had declined, and seedling counts were similar from cultivated and non-cultivated soil. No viable seed remained in the cultivated soil after three years. Emergence from the two lines of fA was very different. Seedling emergence occurred after hot dry con ditions, or in warm periods immediately after periods of chilling, particularly those below 4°C.  相似文献   

2.
Avena fatua L. seed of types fA (brown very hairy lemma) and fB (grey moderately hairy lemma) were collected from six locations in Britain during summer 1974. Primary and secondary seeds were planted separately at 20 and 100 mm depths. Emergence was recorded for 5 years and the number of viable seeds remaining at the end of the experiment was determined. With an increase in planting depth from 20 to 100 mm, there was a decrease in final emergence from secondary seed from 84 to 61% and from primary seed from 93 to 83%. At 20 mm there was no difference in emergence between collections, but at 100 mm there were differences between secondary seeds of some collections. There were also differences in the emergence behaviour of types fA and fB, both between and within collections. More seedlings from primary seeds than from secondary seeds emerged in the early stages, but later the reverse was true. After 5 years secondary seed had produced 16% fewer seedlings than primary seed. Seed unaccounted for at the end of the experiment was 18% for both types, twice as many seeds were unaccounted for at 100 mm than at 20 mm. Likewise, twice as many secondary than primary seeds were unaccounted for. On average the number of viable seeds remaining at the end of the 5 years was less than 1%, although 23% of secondary seeds of type fA from one collection buried at 100 mm remained viable. Flushes of emergence were correlated with prior experience of periods of temperature below 6°C in the soil. Facteurs qui influent sur la levée de plantules de différentes souches d'Avena fatua L. Des semences d'Avena fatua L. de deux sortes, fA (glumelle brune, très velue) et fB (glumelle grise, moyennement velue) ont été collectionnées pendant l'été 1974 à six endroits en Grand Bretagne. Les semences primaires et secondaires ont été plantées séparément à des profondeurs de 20 et de 100 mm. La levée a été signalée au cours de 5 ans et le nombre de semences viables qui restaient à la fin de l'essai a été déterminé. A mesure quàugmentait la profounder du semis de 20 à 100 mm. la levée définitive diminuait de 84 à 61 % pour les semences secondaires et de 93 à 83% pour les primaires. A 20 mm, aucune différence dans la levée n'a été constatée entre les différentes collections mais à 100 mm. centaines différences se sont fait voir entre les semences secondaires de certaines collections. Des différences ont été constatées aussi dans le comportement des sortes fA et fB en ce qui concerne la levée, différences entre les collections et à l'intérieur d'une collection. Au début, les plants provenant des semences primaires étaient plus nombreux que ceux des secondaires, mais plus tard on a constaté le contraire. Au bout de 5 ans, les semences secondaires avaient produit 16% moins de jeunes plants que les primaires. A la fin de l'essai, 18% des semences des deux sortes avaient disparu, deux fois plus à 100 mm qu'a 20 mm. De même deux fois plus de semences secondaires avait disparu que de semences primaires. En moyenne, moins de 1% des semences restaient aptes à germer au bout des 5 ans; néanmoions, 23% de semences secondaires de la sorte fA dans une des collections, enfouies à 100 mm, étaient toujours viables. Des levées sporadiques se trouvaient correlées à des périodes préalables où la température du sol ne dépassait pas 6°C. Ueber Faktoren, welche das Auflaufen verschiedener Linien von Avena fatua L. beeinflussen Im Laufe des Sommers 1974 wurden an sechs verschiedenen Orten in England Spelzfrüchte der Formen fA (braune, sehr stark behaarte Deckspelzen) und fB (graue, mässig behaarte Deckspelzen) von Avena fatua L. gesammelt. 1. und 2.Spelzfrüchte wurden getrennt in 20 und 100 mm Tiefe ausgesät und während 5 Jahren ihr Auflaufen beobachtet; am Ende der Beobachtungsperiode erfolgte eine Bestandesaufnahme der noch lebensfähigen Samen. Mit zunehmender Saattiefe nahm die Auflaurate für die 2.Spelzfrüchte von 84 auf 61% und für die 1. von 93 auf 83% ab. Bei 20 mm Saattiefe bestanden keine Differenzen im Auflaufen zwischen den an den verschiedenen Standorten gesammelten Mustern; bei 100 mm Tiefe wurden jedoch lokale Unterschiede bei den 2.Spclzfrüchten festgestellt. Es bestanden auch Unterschiede im Auflaufverhalten der Formen fA und fB, sowohl zwischen als auch innerhalb der verschiedenen Standortmuster. In der Anfangsphase der Beobachtungsperiode erschienen mehr Keimlinge aus 1. als aus 2. Spelzfrüchten; später war das Gegenteil der Fall. Im Vergleich zwischen 1. und 2.Spelzfrüchten hatten letztere nach 5 Jahren 16% weniger Pflanzen hervorgebracht als die 1. Für beide Formen (fA und fB) wurden am Ende der Versuchsperiode 18% nicht gekeimte, resp. nicht mehr lebensfähige Samen registriert; in 100 mm Tiefe waren es doppelt so viel als bei 20 mm. Ebenfalls doppelt so viele 2.Spelzfrüchte als 1. waren nicht keimfähig. Im Mittel waren nach 5 Jahren weniger als 1% lebensfähig, obwohl bei einem Standortmuster 23% der 2.Spelzfrüchte in 100 mm Tiefe noch lebensfähig waren. Vorange-gangene Perioden mit Bodentemperaturen unter 6°C waren für gehäuftes Auflaufen verantwortlich.  相似文献   

3.
Wild oat plants of types fA, fB and fC were grown at a constant 15 or 20°C during the period of seed maturation. Seed of the three types differed little in dormancy when grown at 15°C, but at 20°C a larger proportion of seeds of type fA were dormant compared with fB or fC. Overall, dormancy of seed produced at 15 and 20°C was 97 and 63% respectively. Plants of another collection of type fB were grown from seed at 15 or 20°C with or without water stress applied only from the time of panicle emergence. Water stress and high temperature reduced viable seed production. Seed dormancy was tested immediately after collection by planting the seed in soil, and by Petri dish tests. Further Petri dish tests were made after 6 months storage. Seedling emergence in the first autumn from seeds of plants matured without water stress at 15°C was 10% compared with 30% for seeds grown at 20°C. Seeds grown with water stress at 15°C gave 47%, and at 20°C 78% emergence. The majority of emergence from seeds formed at 15°C without water stress occurred in the second spring after burial. Petri dish tests support these findings and suggest that seeds produced in hot dry summers are less dormant than those produced in cool moist ones.  相似文献   

4.
B. J. WILSON 《Weed Research》1985,25(3):213-219
Avena fatua was sown in a cultivation experiment in the autumn of 3 successive years. For each population seedling emergence and viable seeds in the soil were recorded for 4 years in crops of winter barley in which new seed production was prevented. About half of the seeds sown were recovered after 1 year. In subsequent years viable seeds in the soil declined more rapidly with tine cultivation than with ploughing. After 4 years up to 5% of the original seeds were still viable. One population exhibited greater seed dormancy than the other two populations, due it is thought to higher summer rainfall and the greater availability of moisture during seed maturation. Most seedlings emerged in the autumn and spring, between 12 and 18 months after sowing. A total of 950 seedlings emerged from 12 000 seeds sown; 21% of these seedlings came from new seeds (< 1 year old), 57% from seeds 1–2 years old, 14% from seeds 2–3 years old and 8% from seeds 3–4 years old. Autumn seedlings arose fairly evenly from all age groups while spring seedlings mostly came from the 1–2-year-old seeds. With tine cultivation total seedlings over 4 years represented 9–7% and with ploughing 6–2% of the original seeds sown. A. fatua was more persistent than in previous experiments in spring barley, which suggests that control measures would have to be applied for longer in a succession of winter cereals than spring-sown crops to reduce A. fatua to low populations.  相似文献   

5.
Dormancy of seeds harvested from excised Avena fatua panicles grown in solutions containing sucrose increased with increasing concentrations of sucrose. Induction of this sucrose-imposed dormancy could be partially inhibited by the inclusion of GA4/7 in the growing medium. The sucrose-grown seeds were fully viable and dormancy could be broken by methods commonly used to break dormancy, such as treatment with GA3 or dehusking and pricking the caryopsis. Low concentrations of sucrose added to the incubation medium stimulated GA3-induced α-amylase synthesis in mature de-embryonated A. fatua caryopses but higher concentrations inhibited it. The relevance of these findings to the explanation of the environmental component of A. fatua seed dormancy is discussed.  相似文献   

6.
Control of Avena fatua (L.) (wild oat) with diclofop methyl applied at 0·7 kg ha?1 at the two-leaf stage and difenzoquat at 0·84 kg ha?1 at the four-leaf stage in wheat (Triticum aestivum L.) under field conditions was good and not affected when either of these herbicides was mixed with 3,6-dichloropicolinic acid as the monoethanolamine salt at 0·14, 0·20 or 0·30 kg ha?1. In the glasshouse, mixtures containing 3,6-dichloropicolinic acid at rates as high as 0·6 kg ha?1 also did not affect control of A. fatua. When barban at 0·35 kg ha?1, or flamprop methyl at 0·56 kg ha?1 was mixed with similar rates of 3,6-dichloropicolinic acid and applied at the two-leaf and four-leaf stage of A. fatua respectively, a reduction in control of A. fatua (antagonism) occurred under both field and glasshouse conditions. The herbicides for control of A. fatua did not influence the fresh weight suppression of C. arvense shoots obtained in the glasshouse with 3,6-dichloropico-colinic acid at 0·3 kg ha?1. Early tolerance of wheat (cv. Neepawa) was acceptable with all mixtures. Wheat yields with diclofop methyl or difenzoquat alone or in mixture with 3,6-dichloropicolinic acid were increased over the yields from the A. fatua-infested control.  相似文献   

7.
This study examined the effects of competition on the growth of Avena fatua, winter wheat and winter barley. Plants were sampled at frequent intervals from replacement series experiments at two contrasting sites in the U.K. A. fatua was much slower to establish than the two cereals, but thereafter exhibited a faster rate of growth. In monoculture, it took a considerable time for A. fatua to reach a size equal to that of the cereals, but by the end of the experiments it was the largest of the three species. The change-over from cereal dominance in mixtures to A. fatua tiominance was rapid, and in three cases coincided with cereal flag leaf emergence. In the fourth case, it appeared to coincide with the art of canopy height extension. At one site the rder of competitiveness at anthesis was A. fatua= barley>wheat, and at the other site the order was A. fatua>wheat>barley. In order to explain and predict differences between years and sites, more studies are required on morphological development in relation to abiotic variables.  相似文献   

8.
Various control strategies for Achillea millefolium L. (yarrow) were investigated in a dense stand of the weed at Lincoln College in 1977–1978. In early spring plots were either rotary cultivated or left undisturbed. In late spring, plots of both previous treatments were either left undisturbed, rotary cultivated or sprayed with glyphosate at 1·5 kg ha?1. The whole experiment was rotary cultivated twice 1 week later and sown with Hordeum vulgure L. cv. Zephyr (barley) at 144 kg seed ha?1. MCPA + dicamba at 0·9+0·15 kg ha?1 was applied to half of each plot when the second node was detectable (Zadok 32). Rotary cultivation and glyphosate both substantially reduced the regrowth of A. millefolium but glyphosate reduced regrowth by a greater proportion when applied to undisturbed plants than when applied to plants regenerating after cultivation. Both gave a more than 95% reduction compared to the control (rotary cultivation only at sowing time) in the amount of A. millefolium present in the barley stubble in the autumn. MCPA + dicamba caused seedling mortality but did not affect the numbers of primary shoots from rhizome fragments. The grain yield of the barley increased from 2·91 t ha?1 when A. millefolium was not controlled to 4·23 t ha?1 with good control. The barley yield appeared to be restricted by competition from regenerating A. millefolium and by a nitrogen deficiency induced in some regimes by nitrogen immobilization in decaying rhizomes.  相似文献   

9.
The feasibility of achieving selective wild oat (Avena fatua L.) control in a stand of the Australian oat (Avena sativa L.) cv. Savena I was examined. Diclofop-methyl was applied at rates of 0·4–0·7 kg a.i. ha?1 at the three- and five-leaf stages of A. fatua (84–132 culms m2). Although all rates of diclofop-methyl caused initial chlorosis and necrosis to the crop, the subsequent control of A. fatua permitted increased crop tillering. Avena fatua control and crop yield response were maximized when diclofop-methyl was applied at the three-leaf stage. Crop grain yield was increased by as much as 32% and 22% during 1984 and 1985, respectively. In the absence of A. fatua competition, crop shoot dry weight at ear emergence was reduced only where diclofop-methyl was applied at 0·6 or 0·7 kg ha?1. However, final grain yield was not reduced by any treatment. Only 11 of 240 cultivars or lines tolerated diclofop-methyl, and none reached the level attained by Savena I and a closely related Australian line [(Irwin × (West × New Zealand Cape/42)) × West]/24. The nature of the inheritance of diclofop-methyl tolerance was examined (1983–1985) by crossing and backcrossing (BC) Savena I with four diclofop-methyl susceptible, but agronomically superior, lines. Inheritance of diclofop-methyl tolerance appeared to be controlled by two genes, with susceptibility being dominant to tolerance in F3, BCIF2 and BCIF3 lines.  相似文献   

10.
Changes in the numbers of Avena fatua seed, incorporated into soil, were monitored in four successive spring barley crops which were harvested early for silage to prevent seed shedding. In the first year there were four times as many seedlings after tine cultivation compared with ploughing, but this was reversed in the second year as re-ploughing brought up dormant seeds and gave more seedlings than tine cultivation. Only 11–14% of the sown seeds produced seedlings during the 4 years. When the seeds were first buried to 25 cm by ploughing, and the barley was direct drilled without cultivation, only 0.4% emerged as seedlings. Few viable seeds remained in the soil after 4 years whether the soil was cultivated annually or not but seed numbers decreased more rapidly with tine cultivation than with ploughing. A few of the deeply buried seeds persisted where the land was direct drilled without cultivation.  相似文献   

11.
Although magnesium (Mg) is considered an essential element for wheat growth, its importance for disease control has often been overlooked, and the physiological features of diseased plants mediated by Mg remain elusive. In this study, the effect of three Mg concentrations (0·25, 2·5 and 4 mm ) on wheat resistance to leaf blast (Pyricularia oryzae), leaf gas exchange, invertase activity, cellular damage and foliar concentration of photosynthetic pigments and nutrients was investigated. Foliar Mg increased from 1·9 to 3·9 g kg?1, whereas calcium (Ca) decreased from 7·8 to 4·9 g kg?1 as the applied Mg increased from 0·25 to 4 mm . Blast severity increased from 11·3 to 39·6% as the applied Mg increased from 0·25 to 4 mm . Photosynthesis, stomatal conductance, transpiration and photosynthetic pigment concentrations decreased in inoculated plants compared to non‐inoculated plants regardless of the Mg concentration; however, the reductions were more pronounced for plants grown with 4 mm Mg than those grown with 0·25 mm Mg. On the other hand, a higher internal CO2 concentration, invertase activity and malondialdehyde concentration was recorded in inoculated plants grown with 4 mm Mg compared to those grown with 0·25 mm Mg. In conclusion, reduced Ca uptake may partially explain the increased susceptibility of wheat to leaf blast with the highest Mg concentration. Mg‐induced susceptibility to leaf blast appeared responsible for the photosynthetic impairments. These were most probably due to biochemical constraints because plants grown with the highest Mg concentration suffered extensive cellular damage and degradation of photosynthetic pigments as a result of high disease severity.  相似文献   

12.
Seeds of Avena fatua L. and )A. sterilis L. were germinated under a wide range of temperatures (5–30°C) and osmotic potentials (?25 to ?1400 KPa) in order to characterize their responses to these two environmental factors. Although both species behaved similarly at moderate temperatures, different responses were observed at the two extremes. )A. sterilis germinated and emerged in a higher proportion than A. fatua at temperatures below 10°C but the opposite was true at temperatures above 20°C. Although the rates of these two processes were similar in both species up to 18°C, above this temperature the germination and emergence of )A. sterilis was considerably delayed in comparison with that of A. fatua. The effect of decreasing osmotic potentials in reducing the germination was more pronounced in A. sterilis than in A. fatua. However, no differences were observed in the emergence responses of either species. The adaptative advantages of these characteristics and their relationship with the geographic distribution of the two species is discussed.  相似文献   

13.
The effects of eight plant protection chemicals on the development of vesiculararbuscular mycorrhizas were influenced by the identity of the host plant and fungal endophyte, the soil type, and the composition and concentration of the biocide. These effects ranged from stimulatory (as with the fungicide chloroneb, applied to inocula of Glomus microcarpus used with pot-grown lettuce), through negligible (aldicarb on G. mosseae in pot-grown onions and field grown barley with indigenous mycorrhizal fungi) to short-term inhibition (drazoxolon on G. mosseae in onion) and longer term inhibition (the fungicides benomyl and triadimefon on G. mosseae in onion).  相似文献   

14.
Summary. A 2-year comparison of the development of Avena fatua L. and Sinapis arvensis L., with spring barley and of Alopecurus myosuroides Huds, with winter wheat gave the following results:
  • 1 Avena fatua emerged shortly before barley in both years. Development until tillering was somewhat slower than that of barley, but after tillering the growth of both species was about the same. The first seeds of A. fatua matured shortly before harvest.
  • 2 Growth of Sinapis arvensis was slower than that of barley during the- early stages, but after tillering was more rapid. Growth ceased more than 10 days before harvest.
  • 3 In 1962–63 Alopecurus myosuroides germinated mainly in spring, but in 1963–64 most germination occurred in autumn, so that early development was different in the two years. After tillering the development WAS much faster than that of wheat and at the flowering stage of A. myosuroides, the shoots were taller than those of wheat. Seed was ripened some time before harvest.
  • 4 A comparison of the development of A. myosuroides and Avena fatua alone and in competition with cereals revealed no marked influence of competition on the pattern of development, but competition did cause some reduction in shoot length and a marked reduction in weight of the two weed species.
Compétition entre plantes cultivées et mauvaises herbes. I. Développement absolu el développement retalif des céréales et de quelques espèces de mauvaises herbes  相似文献   

15.
A. M. BLAIR 《Weed Research》1978,18(6):381-387
Chlortoluron, isoproturon and metoxuron applied to wheat (Triticum aesitvum (L.)), A vena fatua (L.) and Alopecurus myosuroïdes (Huds) at sowing caused less damage if the herbicides were restricted to the region above the seed by an activated charcoal layer. AH three herbicides, when applied to seedlings of the same species also had their main activity through the soil, an activated charcoal layer at seed level decreasing damage from post-emergence sprays of isoproluron. Germination and/or establishment of A. myosuroïdes was better from seeds sown at or near the surface, hut the reverse was true for A. fatua, which showed weak germination and/or establishment from seed on the soil surface. Rechterches sur les sites d'absorption du chhrtoluron, de l'isoproturon et du métoxuron par le blé. A vena fatua et Alopecurus myosuroïdes Le chlortoluron, l'isoproturon et le métoxuron appliqués au semis sur du blé (Triticum avstivum (L.), Avena fatua (L.) et Alopecurus myosuroïdes (Huds.) ont causé moinsde dommages si les herbicides restaient localises dans la region située audessus des semences grâce à une couche de charbon activé. Les trois herbicides, lorsqu'ils furent appliqués aux plantules des mêmes cspèces, ont aussi exercé leur principale activitéà travers le sol; une couche de charbon active au nivcau des semences a dim inué les dommages provoques pour des traitements effectues avee de l'isoproturon en posttevée. La germination atnsi que l'etablissement d'A. myosuroïdes ont été meilleurs à partir de sentences semées en surface, ou prés de la surface mais ce fut l'inverse pour A. fatua qui montra une germination et un etablissement plus faibles lorsque le semis a été fait en surface. Untersuchungen zum Ort der Aufnahme von Chlortoluron. Isoproturon und Metoxuron bei Weizen, A vena falua und A lopecurus myosuroides Wenn Chlortoluron, Isoproturon und Metoxuron zu Weizen (Triticum aestivum (L.)), Arena fatua (L.) und Alopecurus myosuroïdes (Huds.) zum Zeitpunkt der Saat appliziert wurden, traten weniger Schäden auf. wenn die Herbizide durch eine Aktivkohlcschicht oberhalb der Samen verblieben. Auch wenn die Herbizide auf junge Pflänzchen appliziert wurden, wirkten sie hauptsachlich über den Boden Durch eine Aktivkohleschicht in der Samenzone wurde die Wirkung von Nachauflaufbehandlungen mil Isoproluron abgeschwächl. Bei A myosuroïdes war die Keimung und/oder das Wachstum besser, wenn sich die Samen auf oder nur knapp unterhalb der Bodenoberfläche befanden. Bei A. fatua was es urngekchrt, hier war die Keimung und/oder die Entwicklung nur schwach. wenn sich die Samen auf dem Boden befanden.  相似文献   

16.
Buried populations of dormant and non-dormant wild oat (Avena fatua) seed persisted less than 2 years, depth of burial having very little influence on their survival. The mode of seed disappearence, however, was closely related to their depth in the soil. Seed exhaustion through germination in situ increased with increasing depth in the soil, whereas exhaustion through non-viability increased with decreasing depth. Physical and induced dormancies are apparently not capable of supporting prolonged persistence of A. fatua seeds in soil. The lack of prolonged persistence of A. fatua seeds in Colorado derives from a lack of genetically programmed embryonic dormancy in these populations and makes A. fatua easier to control in Colorado than in other cereal-growing regions south of the 43rd parallel because it dramatically reduces the survival of seeds in the soil. The most effective non-chemical control of this grass weed is achieved by means of the shallowest cultivations possible, carried out as late as possible.  相似文献   

17.
土层深度对三种麦田禾本科杂草出苗及生长的影响   总被引：1，自引：0，他引：1  
为明确小麦田禾本科杂草在不同土层深度的出苗及生长情况,选取雀麦Bromus japonicas、节节麦Aegilops tauschii和野燕麦Avena fatua三种小麦田常见禾本科杂草,采用盆栽法系统研究不同土层深度对杂草出苗及生长的影响。结果表明,小麦田禾本科杂草雀麦、节节麦和野燕麦出苗和生长与不同土层深度密切相关,在浅土层中均有较好的出苗率,且后期生长也正常。从出苗时间来看,雀麦和野燕麦集中出苗时间在播种后5～11 d,节节麦略晚于这2种杂草;从最适出苗土层深度来看,雀麦最适出苗土层深度为0.5～3.5 cm,出苗率在76.0%～87.0%之间,节节麦的最适出苗深度为0.5～8.0 cm,出苗率在66.7%～79.3%之间,而野燕麦的最适土层深度为0.5～18.0 cm,出苗率达84.2%～94.4%;从出苗后生长影响来看,0～20 cm土层对野燕麦后期生长没有显著影响,土层深度大于10.0 cm对节节麦生长有显著抑制作用,大于6.0 cm即对雀麦有显著影响。研究表明通过深翻土地可以对雀麦和节节麦达到一定的控制作用,但对野燕麦控制效果相对略差。  相似文献   

18.
Experiments are described in which plants from six different populations of the outbreeding annual weed Tripleitrospermum inodorum were grown with barley in field plots and sprayed with 4-chloro-2-melhyIphenoxyacetic acid (MCPA) at a number of doses. The populations showed significant differences in reduction of weight, the most resistant population having an ED50 of 181 ± 36·9 mg/m2 a.e. MCPA, 2·49 limes as great as the ED50 of the least resistant population. In a second experiment in which plants from these two populations were again grown with barley in field plots and sprayed with several doses of MCPA at three different stages of growth, their resistance to MCPA was found to differ consistently at all three stages of growth, the more resistant population having a mean LD50 of 1103 ± 161·5 mg/m2 a.e. MCPA, 2·09 times as great as the mean LD50 of the less resistant population. The populations were similar in other respects. The differences in the spraying histories of the two populations were consistent with the supposition that the differences in resistance to MCPA had resulted from natural selection for MCPA resistance in the more intensively sprayed population, but other processes may also have been involved.  相似文献   

19.
Seeds from seven genetically inbred pure lines of wild oats (Avena fatua L.) with different levels of dormancy and viability were analysed for seed-borne fungi. All lines had fungi on the seeds. The predominating fungi were Alternaria alternata and Cladosporium herbarum, of which the latter was non-pathogenic and the former only weakly pathogenic on seedlings of wild oats. Drechslera avenacea, Cochliobulus sativus and Fusarium spp., frequently isolated, were pathogenic on A. fatua. Only D. avenacea was host specific to A. fatua and cultivated oats Avena sativa. Cochliobolus sativus and Fusarium spp, were equal or more pathogenic on seedlings of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oats and rye (Secale cereale L.) than on seedlings of A. fatua. Drechslera avenacea occurred on a significantly higher percentage of seeds from A. fatua lines, AN 51 and AN 474, than from the other lines. Other fungi isolated occurred randomly on all A. fatua lines. There was no relationship between low viability of seeds and fungi carried on the seeds.  相似文献   

20.
ADKINS  TANPIPAT  SWARBRICK  BOERSMA 《Weed Research》1998,38(2):129-138
Glasshouse experiments were conducted to determine the effects of soil moisture content, irradiance, temperature and relative humidity on the efficacy of glyphosate applied to six isogenic lines of Avena fatua L. (wild oat) and four near-isogenic lines of Urochloa panicoides Beauv. (liverseed grass). The variables examined were four soil moisture conditions (29%, 42%, 55% and 100% of field capacity), two levels of irradiance (400 and 800 μmol m?2 s?1), two levels of relative humidity (>92% and 65%) and four temperature regimes (20/15, 25/20, 30/25 and 35/30 °C: day/night), representing the environmental conditions of winter or summer fallows in the north-east grain region of Australia. The efficacy of 360 g acid equivalent ha?1 glyphosate was greatest under well-watered (100% of field capacity), warm (30/25 °C for A. fatua and 35/30 °C for U. panicoides) and humid (>92/90%) conditions. The efficacy was least under severe water stress (29% of field capacity), warm (30/25 °C for A. fatua and 35/30 °C for U. panicoides) and moderately humid (65/60%) conditions. Efficacy was not altered by the level of irradiance nor was it different between isogenic lines.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号