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1.
Lithospermum arvense is an increasing annual weed in winter crops of the semiarid region of southern Argentina under low impact tillage systems, an agricultural practice that has become popular in recent years. Seed distribution in the soil profile under conventional tillage will change when reduced tillage is implemented, thus affecting the germination microenvironment. The effect of seed burial depth and soil water regime on field germination, enforced dormancy, innate dormancy and seed decay was studied in relation to burial time in a field experiment. In addition, the effect of burial depth on seed germination and seedling emergence was examined under laboratory controlled conditions. Field germination of buried seed ranged from 55% to 65% for shallow (2 cm) and from 5% to 30% for greater depths (20 cm). Enforced dormancy levels were significantly higher among deeper seeds. The amount of innate dormant seeds was reduced to <10% after a year of burial. Lithospermum arvense seedbanks can be classified as short-term persistent. Germination in the laboratory was unaffected by burial depth, while seedling emergence reduction was adequately described by a sigmoidal model. Results indicate that agricultural practices that accumulate L. arvense seeds near the soil surface enhance seedling recruitment. 相似文献
2.
Parthenium hysterophorus L. seeds were buried at a depth of 5 cm for periods of 2–24 months to determine their longevity. The majority (73.7%) of these seeds were still viable after 24 months of burial. The remainder could not be recovered (18.0%) or were no longer viable (8.3%). There was a log-linear decline in persistence of germinable seeds over time, which indicated a constant rate of loss and a half-life of about 6 years. Seedling emergence from surface-sown seeds was also studied. Although there was considerable rainfall (31 mm), seedlings did not emerge during the first month of this experiment. In the succeeding 3 months, there was substantial seedling emergence after rainfall, and 51.4% of seeds had germinated by the end of the fourth month. After 5 months had passed, further seedling emergence was not detected, and intact seeds could not be located. These findings suggest that seed incorporation into the soil is important to the long-term persistence of P . hysterophorus seeds. In an initial test of germination, unburied seeds from the same seed lot exhibited a degree of innate dormancy, and this may explain the delayed germination observed in the surface-sown seeds. In the seed burial and recovery experiment, innate dormancy was lost after 2 months of burial in the field, although in situ germination of buried seed remained low for at least 24 months. Therefore, it appears that more than one dormancy mechanism may contribute to the persistence of P. hysterophorus seeds. 相似文献
3.
The data on seed population dynamics of three weedy species of Eupatorium, viz. E. adenophwrum Spreng., E. riparium Regel and E. odoratum L. have been presented and discussed in the paper. The seed production and seed populations in soil seed bank were estimated, and the fate of buried seeds in soil was followed over a 2-year period. All the three species of Eupatorium produced a large number of seeds. The seed production of E. riparium per unit area was higher than that of the other two species because of its high population density. In all the three species most of the seeds were found to be present in the top 2 cm of the soil. The viable seed population of the three species of Eupatorium declined exponentially alter their burial in soil showing almost similar mortality patterns. A large proportion of seeds of all the Eupatorium spp. remained under enforced dormancy during their burial in soil with only a small fraction exhibiting induced dormancy. The longevity of the buried seeds increased on account of the dormancy imposed on them. The loss of seeds through degeneration and/or decomposition was rather low. 相似文献
4.
HANWEN WU STEVE WALKER MICHAEL JONATHAN ROLLIN DANIEL KEAN YUEN TAN GEOFF ROBINSON JEFF WERTH 《Weed Biology and Management》2007,7(3):192-199
Flaxleaf fleabane ( Conyza bonariensis [L.] Cronquist) is a difficult-to-control weed in dryland minimum tillage farming systems in the northern grains region of Australia. Experiments under field and controlled environments were conducted to study the seed germination, emergence, and persistence of C. bonariensis . The base, optimum, and maximum temperatures for seedling germination were estimated at 4.2, 20, and 35°C, respectively, with light stimulating germination. The soil types and burial depths had significant effects on seed persistence and emergence. The persistence pattern showed an initial rapid drop, followed by a slow but steady decline over time. After 3 years of burial, there were ≈ 7.5%, 9.7%, and 1.3% viable seeds at 10, 5, and 0–2 cm soil depths, respectively. Conyza bonariensis predominantly emerged from the soil surface or from the burial depth of 0.5 cm. Very few seeds emerged from a depth of 1 cm and none emerged from ≥ 2 cm. The emergence was greater in lighter soils. On-farm monitoring of the field emergence over time in a light sandy loam soil showed that 99% emergence occurred in late autumn, early and late winter, and a small fraction of 1% emerged in mid-spring. The predominant emergence from the soil surface suggests that the fleabane problem is a result of weed species shift toward the minimum tillage systems that provide moist conditions for better emergence compared to conventional tillage systems. The seed longevity of at least 3 years in the soil and the prolonged emergence patterns between autumn and spring have posed great difficulties for the long-term management of C. bonariensis . 相似文献
5.
Common ragweed (Ambrosia artemisiifolia L.) is one of the annual plants that were described recently as invasive weeds in Europe. This species is described as an invasive plant that produces seeds that are highly variable. Its production of variably sized seeds is regarded as promoting its spread in different environments. Experiments were carried out to determine the influence of the seed weight and temperature on germination and the influence of the seed weight and burial depth on seedling emergence. The seeds were divided into a number of classes of weight and the seed weight effect on germination was evaluated by Petri dish assays. In another experiment, the seeds were buried at different depths in a clay soil/sand mix to estimate the burial effect on germination and seedling emergence. The germination level of A. artemisiifolia was high overall, between 76.8% and 94.2%. The seed germination was modified by temperature but it was not influenced by the seed weight. The amounts of germination and seedling emergence were greater for the seeds on the soil surface and decreased with an increasing burial depth, from 2 to 8 cm. No germination or emergence was observed for the seeds that were buried at 10 and 12 cm. The lightest seeds were more sensitive to burial. A greater level of seedling emergence for those seeds that were placed near the soil surface could explain the success of this species in open habitats, where the probability of deeper burial is low. After high seed production, the management of A. artemisiifolia in fields could be partly achieved through soil tillage, burying seeds below 10 cm, and not carrying out deep soil tillage the following year. 相似文献
6.
Changes in germinability, dormancy and viability of Amaranthus retroflexus as affected by depth and duration of burial 总被引：2，自引：0，他引：2
Changes in dormancy and viability of Amaranthus retroflexus seeds were examined after placement in pots that were buried in the field. Seeds were placed in woven nylon envelopes on the soil surface or buried at depths of 2.5, 5 or 10 cm. After 1, 3, 6, 9 and 12 months seeds were exhumed and their germinability was tested to assess changes in dormancy and viability. Depletion of seed stocks placed on the soil surface was partly because of in situ germination that did not exceed 21% and did not vary significantly over the 12-month study period. Less germination of buried seeds occurred in situ , and seeds that did not germinate appeared to acquire dormancy. Exhumed seeds germinated readily; germinability was linearly related to the depth of burial, with those retrieved from the surface germinating least. Cyclical changes in germinability occurred during the 12-month burial period, but this influence was identical for seeds buried at all depths. Germinability was greatest after periods with the lowest mean monthly temperatures and least during the hottest periods. The stimulation of remaining ungerminated seeds exhumed at each period, by the addition of ethephon to the germination medium, provided further evidence of a seasonal acquisition of dormancy, and it was concluded that other unknown factors besides cyclical changes in seasonal temperature were responsible. Irrespective of placement, all seeds lost viability at an exponential rate over time. However, the decline was most rapid for those placed on the surface, whereas the loss in viability became less with increased depth of burial. Possible explanations for this adaptation of enhanced survival when buried are discussed. 相似文献
7.
Seed populations of Avena sterilis ssp. ludoviciana (Durieu) Nyman were monitored in a naturally occurring infestation throughout its life cycle. Considering the large weed population present (298panicles m?2), total seed production was relatively low: 3838 seeds m?2. Only 68% of these seeds were recovered from the soil surface and a further 3% were removed with wheat grain and straw during harvest operations. The numbers of seeds from the stubble between mid-July and mid-September were relatively low (10%). Ploughing the stubble in October buried most of the recently produced seed rain and resulted in a relatively uniform vertical distribution of the seedbank. Maximum seed persistence in the soil ranged from 27 to 43 months (depending on the experimental technique used to do the study). Seed decline followed an exponential pattern on a yearly basis, with the greatest decline taking place between October and April (57–90% in year 1 and 10–40% in year 2), Between May and September the buried seed populations remained practically constant. Seedbank depletion was primarily due to seedling production (25%) and ‘lethal’ germination (24%). Although the depth of burial had very little effect on seed survival, the mode of seed disappearance was closely related to their depth in the soil. Seed depletion through ‘lethal’ germination increased with increasing depth in the soil, whereas depletion through seedling emergence decreased with increasing depth. 相似文献
8.
The longevity of buried Rottboellia cochinchinensis (Lour.) W.D. Clayton seed represents a major survival mechanism for the weed, enabling the persistence of a continuing source of weed seeds in crop land. The pattern of seed persistence and depletion of R. cochinchinensis in cultivated maize soils was investigated by means of (1) studies on the effect of depth and duration of burial on the viability of the weed seeds, (2) quantitative estimation of the seed population and viability in cultivated fields, and (3) the periodicity of emergence and effects of cultivation on seed germination both in the field and in the greenhouse. The results indicated that the mode of persistence was innate (8.5%) and enforced (35%) dormancy after 1 year of burial, and that the persistency component of the seed population on cultivated soils ranged from 40.60%. The weed was able to remain viable at depths of 45 cm, indicating an excellent mechanism of escaping the effects of most soil-applied herbicides, and it was shown that tillage increases the depletion rate of the weed seed reserve by 32% per year. 相似文献
9.
Weed seed predation is an ecosystem service, influencing weed population dynamics. The impact of weed seed predation on weed population dynamics depends on how predators respond to seed patches at the field scale. Seed predation will be most effective if the proportion of seeds predated increases with increasing size and seed density of patches. Density‐dependent rodent seed predation was measured by varying seed density and patch size in four irrigated conventionally managed cereal fields in north eastern Spain. Artificial weed seed patches were created by applying a range of Lolium multiflorum seed densities from 0 to 7500 seeds m?2 in 225 m2 patches (2008) or in patches that varied in size from 1 to 9 m2 (2009). Seed predation was estimated using seed cards and seed frames. The granivorous rodents Mus spretus and Apodemus sylvaticus caused high seed predation rates (92%) in three fields, whereas in a fourth field, it was lower (47%). Rodents responded in an inversely density‐dependent manner, but this had little biological meaning as even in patches seeded with the highest density, the input to the soil seedbank was reduced by 88%. For the period of time this experiment lasted, hardly any new seeds would have entered the seedbank. 相似文献
10.
S. R. MOSS 《Weed Research》1987,27(5):313-320
Alopecurus myosuroides Huds. was studied over a 2-year period in winter wheat established after tine cultivations or direct drilling. Straw was removed by baling or spread and burnt. Seed production was either allowed or prevented by cutting and removing all vegetation at the end of the first year. Cultivation differences had no consistent effect on plant or seed populations. Straw burning destroyed about 50% of seeds and encouraged the germination of surviving seeds. Weed populations in the crop were lower on burnt than on baled areas. Where seed shedding was allowed, populations of seeds in soil and plants increased by up to nine-fold per year. Straw burning resulted in smaller population increases. Seed decline in the soil averaged about 80% per year, so that less than 6% of the weed seeds sown were still viable after 2 years’burial in the soil. Most of the seed decline occurred between July and October and was slightly greater on burnt than on baled areas. Only part of this seed loss was accounted for by germination and emergence of seedlings during summer and autumn. Plants emerging in the crop represented less than 26% of viable seeds present in the soil at time of drilling the crop. Few seedlings emerged in spring. The viability of shed seeds varied with year and with weed density. High infestations were associated with lower seed viability and also fewer heads per plant. 相似文献
11.
Embryos in freshly matured seeds of the facultative winter annual Papaver rhoeas are underdeveloped and physiologically dormant; thus, seeds have morphophysiological dormancy (MPD). Seeds lost physiological dormancy during 12 weeks of burial in moist soil at 12 h/12 h daily alternating temperature regimes of 15/5°C, 20/10 °C and 25/15 °C but not at 1 °C. Physiological dormancy was not broken in seeds stored dry at room temperature for 12 weeks. After physiological dormancy was broken, seeds required light for embryo growth (i.e. for loss of morphological dormancy) and consequently for germination. After a 12-week period of burial in soil at 25/15 °C, seeds that matured in 1997 germinated to 100% in light at 25/15 °C, demonstrating that cold stragification temperatures (≈ 0.5–10 °C) are not required for embryo growth. Thus, seeds have non-deep simple MPD. During exposure to low winter temperatures (5/1 °C, 1 °C), 52% of the seeds with physiologically non-dormant embryos entered conditional dormancy and thus lost the ability to germinate at 25/15 °C but not at 15/5 °C or 20/10 °C. The peak of germination for seeds sown in southern Sweden was in autumn, but some also germinated in spring. A higher percentage of seeds that matured in a relatively warm, dry year (1997) came out of MPD and germinated than did those that matured in a relatively cool, wet year (1998) at the same site. 相似文献
12.
Effects of environmental factors and burial depth on seed germination and emergence of two populations of Caucalis platycarpos 
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下载免费PDF全文 Caucalis platycarpos is a weed species in irrigated and dry land farming systems in East Azerbaijan and Kermanshah provinces of Iran. Experiments were undertaken to compare C. platycarpos seed germination and emergence of a population from each province over a range of environmental factors, burial depth and crop residue treatments. The Azerbaijan population required lower temperatures (20/10°C day/night temperature) for its highest (90%) germination, compared with the Kermanshah population (88% germination at 25/15°C day/night temperature). In both populations, germination was 84–90% over a wide range of light/dark periods (10–24 h light), but considerable reduction (up to 42%) occurred under continuous darkness. The osmotic potential required for 50% inhibition of germination was ?0.54 and ?0.40 MPa for Azerbaijan and Kermanshah populations respectively. The NaCl concentration of 8.83 and 5.71 dS m?1 caused 50% inhibition of germination in Azerbaijan and Kermanshah populations respectively. The X50 parameter (the burial depth at which emergence is reduced by 50%) for Azerbaijan and Kermanshah population was 2.18 and 2.86 cm respectively. Crop residues had more inhibitory effects on the Azerbaijan than Kermanshah population. Adaptive differentiation of C. platycarpos populations has also resulted in smaller seeds of the Azerbaijan compared with the Kermanshah population and resulted in higher emergence for Kermanshah population seedlings from greater soil depths. These results suggest that differences in germination requirements, drought and salinity tolerance of C. platycarpos populations are correlated with environmental conditions of the habitats of the studied populations. 相似文献
13.
Mimosa pudica (common sensitive plant) is a problematic weed in many crops in tropical countries. Eight experiments were conducted to determine the effects of light, seed scarification, temperature, salt and osmotic stress, pH, burial depth, and rice residue on the germination, seedling emergence, and dormancy of M. pudica seeds. Scarification released the seeds from dormancy and stimulated germination, though the germination of the scarified seeds was not influenced by light. The scarification results indicate that a hard seed coat is the primary mechanism that restricts germination. The germination increased markedly with the exposure to high temperature "pretreatment" (e.g. 150°C), which was achieved by placing non-scarified seeds in an oven for 5 min followed by incubation at 35/25°C day/night temperatures for 14 days. The germination of the scarified seeds was tolerant of salt and osmotic stress, as some seeds germinated even at 250 mmol L−1 NaCl (23%) and at an osmotic potential of −0.8 MPa (5%). The germination of the scarified seeds was >74% over a pH range of 5–10. The seedling emergence of the scarified seeds was 73–88% at depths of 0–2 cm and it gradually decreased with an increasing depth, with no seedling emergence at the 8 cm depth. The rice residue applied to the soil surface at rates of ≤6 t ha−1 did not influence the seedling emergence and dry weight. The information gained from this study identifies some of the factors that facilitate M. pudica becoming a widespread weed in the humid tropics and might help in developing components of integrated weed management practises to control this weed. 相似文献
14.
P K JENSEN 《Weed Research》2009,49(6):592-601
Persistence of seeds of the four winter annual grass species, Alopecurus myosuroides , Bromus sterilis , Bromus hordeaceus and Vulpia myuros , were studied under field conditions. The studies also included the two dicotyledon species, Tripleurospermum inodorum and Galium aparine . Seed samples were stored in the field at different depths in the plough layer for a year. Following germination, seedling emergence was taken as an indicator of field persistence. In a supplementary investigation, seed samples were placed on the soil surface or buried at 2 cm for a month and then tested for viability. Persistence of the two Bromus species was very short, irrespective of depth and duration of burial. Persistence of the other species was positively correlated with incorporation of seeds to a few centimetres depth. Increasing the depth of incorporation below 2 cm had a variable influence on persistence. Persistence of seeds placed directly on the soil surface was short, whether they were left there for a year or a month. Whether seeds at the soil surface were left uncovered or covered with chopped straw had limited influence on seed persistence. However, straw cover significantly increased persistence of A. myosuroides seeds and there was the same tendency with T. inodorum . 相似文献
15.
Seeds of Cassinia arcuata R. Br. (sifton bush), collected annually from near Orange (1987-92) and Boorowa (1987-89). New South Wales. Australia, were stored in a laboratory at a mean temperature of 21°C and a mean relative humidity of 25% and germinated each year for up to 8 years. Seeds from the 1990 and 1992 Orange collections were buried 5 mm and 40 mm deep in the soil for 0.5-2.7 years and the number and germinability of recovered seeds recorded. Germination capacity of seeds stored in the laboratory increased during the first 2 years of storage and then declined slightly in year 3 and markedly in years 4 and 5 to very low levels in year 6 and subsequent years. The seeds collected near Orange had nil germination after 6 years'storage, whereas Boorowa seeds still had 0.2% and 3.5% germination after 7 and 8 years'storage respectively. Seeds that failed to germinate were shown to be non-viable by the tetrazolium test. There was no decline in germination rate during the first 3 years of storage, but, thereafter, there was a substantial annual decline, which would reduce the rate of establishment of seedlings in the field and render them susceptible to competition from improved pastures. The longer and deeper the burial of seeds in the soil and the older the seeds, the fewer seeds that germinated when recovered; meaned for both depths of buriai 23% of 0.9-year-old seeds that had been buried for 0.5 years and 3.4% of 5.1-year-old seeds that had been buried for 2.7 years were recovered in a germinable state. The main causes of loss during burial were germination in the soil and destruction by soil organisms. 相似文献
16.
This study investigates the seasonal variation of germination ability of buried seeds of Monochoria vaginalis (Burm.f.) Presl var. plantaginea Solms. The field-collected seeds were buried in a flooded or an upland field and then exhumed monthly. The exhumed seeds were germinated under four temperature regimes. The seeds exhumed from the flooded soil were dormant at the beginning of burial and proceeded into a conditional dormancy/non-dormancy/conditional dormancy cycle throughout the remaining period of the experiment. The seeds exhumed monthly from the non-flooded soil exhibited an annual dormant cycle, which is dormancy/conditional dormancy/non-dormancy/conditional dormancy/dormancy. At day and night temperatures of 25/20 °C, the exhumed seeds from both the flooded and the upland soil resembled each other in terms of seasonal variation of the germination percentage. In September and October, more seeds exhumed from upland soil failed to germinate under higher temperature than from flooded soil. Strictly avoiding exposure to light during seed exhuming and seed testing prevented the seeds from germinating. A short exposure of the exhumed seeds to light during preparation promoted dark germination when the seeds were at the non-dormant stage. The potential implications of our results for weed management strategies in rice production are discussed. 相似文献
17.
Summary Germination of Phalaris minor declined with the increase in duration of imbibition in water from 30 min to 72 h at temperatures above 22 °C . Germination was reduced down to 10 cm and 2 cm soil depth by wheat straw burning in puddled and non-puddled soil, respectively, with maximum reduction near the soil surface. The dormancy of P . minor seed was not more than 60 days under field conditions. In puddled soil, 38–60% of the viable seeds of P. minor remained concentrated in the upper 5-cm layer. Germination decreased with an increase in soil depth. In total, 15% of seeds stored in the laboratory emerged from 10-cm depth, whereas seeds did not germinate below 4.2-cm depth under field conditions. Depth of emergence of P . minor was shallower in zero tillage compared with the conventional method of wheat sowing. The seeds retrieved from rice soils kept under continuous submergence for 60 days exhibited 26% and 57% loss of germination over semi-submergence and semi-wet conditions respectively. There was 100% loss of germination in 10-month-old seeds retrieved from the soil under rice-growing conditions. Plant density of P. minor was lower in zero tillage than with the conventional method of wheat sowing. Cross-ploughing in the upper 2–5 cm of soil (shallow tillage) and drill-sowing of wheat 1 week after shallow tillage reduced germination of P. minor by 44% and 37% and increased grain yield by 21% and 47% over zero-tillage and conventional methods respectively. 相似文献
18.
The survival of Alopecurus myosuroides Huds. seeds in soil 总被引：1，自引：1，他引：0
S. R. MOSS 《Weed Research》1985,25(3):201-211
The survival of Alopecurus myosuroides seeds was studied in soil under arable cropping and short term grass leys in which seed return was prevented. At two winter wheat sites, where weed seeds were sown, the mean annual seed decline was 73–83% over a 2- or 3-year period. The rate of decline was similar with all the cultivation systems studied: ploughing, tine cultivation and direct drilling. Seeds buried initially by ploughing, and then not disturbed by cultivation, were slightly more persistent. At five arable sites with natural populations of A. myosuroides, seed numbers declined to an average of 3% of the original amount present after 3 years, and to 1% after 4 years. Initial populations of over 50 000 seeds m?2 were recorded. Plant populations were not always proportional to the total seed content of the soil, especially on ploughed land. Seed decline in two grass fields was similar to that under arable cropping. A. myosuroides plants were recorded in a wheat crop following a 2-year grass ley. Weed plants did not persist in the vegetative state in grass used for conservation and grazing. At all sites, appreciable quantities of seeds were still present in the soil after 2–4 years. Although a relatively small proportion of seeds survived, the actual number of seeds surviving was substantial. For this reason, it was concluded that any eradication policy is unlikely to be effective in a cropping system dominated by winter cereals. 相似文献
19.
A series of experiments investigated the light sensitivity of buried weed seeds both within and outside the soil gas microenvironment. Light sensitivity of Datura stramonium L. seeds was found to be increased markedly by a period of soil burial; seeds showed a pronounced germination response even in far-red light (724 nm). Despite this elevated light sensitivity (even to less than 0.01% of incident light), soil overlying buried seeds was sufficient to neutralize the germination trigger. Furthermore, in situ irradiation of buried seeds was found to be virtually ineffective as a germination trigger, showing that the gaseous environment surrounding buried seeds may represent the main obstacle to germination. It is suggested in this study that the soil environment restricts the removal of the germination-inhibiting products of fermentation metabolism. This suggestion is supported by the finding that gas exchange within the seed:soil complex, achieved by flushing with nitrogen, partially restores seed light sensitivity. In addition, it was found that with increasing sowing depth, the germination response was attenuated and also became less dependent on seed phytochrome photoequilibrium conditions. This demonstrates that the phenomenon of germination photoinduction can be reversed by other environmental factors that reduce or eliminate phytochrome physiological activity. Finally, it was shown that seed very low fluence response (VLFR) is triggered only when gas exchange around buried seeds co-occurs with light exposure. 相似文献
20.
MINORU ICHIHARA MASAYUKI YAMASHITA HITOSHI SAWADA YOICHI KIDA MOTOAKI ASAI 《Weed Biology and Management》2009,9(3):217-224
Italian ryegrass ( Lolium multiflorum Lam.) is an exotic winter annual weed that recently has seriously infested wheat fields in central Japan. To understand the influence of tillage systems on the germination ecology and seedbank dynamics of naturalized Italian ryegrass, we compared the fate of the seeds that were after-ripened in the soil with that of the seeds on the soil surface, and then examined the germination characteristics of the seeds retrieved from both treatments by germination tests in both a light/dark (12 h photoperiod) condition and in constant darkness. The seedling emergence was greater initially for the seeds after-ripened on the soil surface than for the seeds in the soil. The component of emergent seeds after-ripened on the soil surface increased as time passed during the summer, whereas that of emergent seeds in the soil scarcely increased. This contrasting emergence was, in part, attributable to the ability of the seeds to germinate at higher temperatures in the light/dark condition than in constant darkness. These results suggest that untilled systems, which leave many seeds on the soil surface, might promote the rapid depletion of Italian ryegrass seeds through germination before wheat sowing in early winter. In contrast, seed burial by tillage might inhibit the germination of the seeds and form a large transient seed bank available to germinate during the wheat-growing season. 相似文献