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A Orozco-Segovia A E Brechú-Franco L Zambrano-Polanco† R Osuna-Fernández G Laguna-Hernández & M E Sánchez-Coronado 《Weed Research》2000,40(6):495-506
The effect was studied of sunlight and far-red (FR) light during seed development, on seed quality and germination of Sicyos deppei G. Don. Seeds exposed to FR during development were lighter in colour and their weight, size and water content were significantly lower. Less than 10% of non-scarified freshly harvested seeds germinated. Scarified, freshly harvested seeds developed under sunlight had a partially negative photoblastic response; both red (R) and FR light inhibited germination. The highest and fastest germination occurred in darkness, probably due to the effect of the high photon flux densities on the phytochrome during seed development. Scarified seeds ripened under FR light, germinated well in FR light and in darkness, but R light inhibited germination. After 6 months of storage, the permeability of S. deppei seeds increased, the partially negative photoblastic response was lost and germination of scarified seeds increased. Specifically, in seeds developed under FR, germination in darkness was faster than for the other light treatments, but slow in darkness for seeds developed under sunlight. The physiological and morphological heteroblastic responses in S. deppei probably extend its seed germination and seedling recruitment periods. 相似文献
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通过芽期NaCl胁迫研究了不同浓度NaCl对芝麻种子成苗及幼苗生长的影响,分析了0．4％ NaCl胁迫下不同基因型芝麻的反应差异。结果表明：（1）0～0．4％的NaCl浓度对芝麻种子成苗率影响较小,在NaCl浓度为0．6％～0．8％时表现为成苗率下降;芽长和简易活力指数均随NaCl浓度的增加而不断下降;根长和苗鲜重则因品种不同表现有异,部分品种随NaCl浓度增加呈先升后降趋势,部分品种则表现为不断下降趋势,不同芝麻品种表现差异较大。（2）所有参试品种在0．4％的NaCl浓度胁迫下在根长、芽长、苗鲜重、简易活力指数等测定指标上均表现出下降较为明显,认为0．4％的NaCl浓度胁迫可以作为芝麻种质资源耐盐性筛选鉴定的参考浓度。（3）聚类分析结果将39份种质资源明显聚为两类,即包含12份种质的耐盐类和包含27份种质的不耐盐类。（4）参试的改良品种（系）与地方种质耐盐性差异不大,地方种质的耐盐性指标的多样性指数要大于改良品种（系）,即在NaCl胁迫下地方种质所表现的基因型差异要大于改良品种（系）。 相似文献
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Keyath Nisar Jitendra Kumar MB Arun Kumar Suresh Walia Najam A Shakil Rajender Parsad Balraj S Parmar 《Pest management science》2009,65(2):175-182
BACKGROUND: Infestation of seeds by pests during storage leads to deterioration in quality. Seed coating is an effective option to overcome the menace. Unlike synthetic fungicidal seed coats, little is known of those based on botanicals. This study aims at developing azadirachtin‐A‐based pesticidal seed coats to maintain seed quality during storage. RESULTS: Polymer‐ and clay‐based coats containing azadirachtin‐A were prepared and evaluated for quality maintenance of soybean seed during storage. Gum acacia, gum tragacanth, rosin, ethyl cellulose, hydroxyethyl cellulose, polyethyl methacrylate, methyl cellulose, polyethylene glycol, polyvinyl chloride, polyvinyl acetate, polyvinyl pyrrolidone and Agrimer VA 6 polymers and the clay bentonite were used as carriers. The time for 50% release (t1/2) of azadirachtin‐A into water from the seeds coated with the different coats ranged from 8.02 to 21.36 h. The half‐life (T1/2) of azadirachtin‐A in the coats on seed ranged from 4.37 to 11.22 months, as compared with 3.45 months in azadirachtin‐A WP, showing an increase by a factor of nearly 1.3–3.3 over the latter. The coats apparently acted as a barrier to moisture to reduce azadirachtin‐A degradation and prevented proliferation of storage fungi. Polyethyl methacrylate, polyvinyl acetate and polyvinyl pyrrolidone were significantly superior to the other polymers. Azadirachtin‐A showed a significant positive correlation with seed germination and vigour, and negative correlation with moisture content. CONCLUSION: Effective polymeric carriers for seed coats based on azadirachtin‐A are reported. These checked seed deterioration during storage by acting as a barrier to moisture and reduced the degradation of azadirachtin‐A. Copyright © 2008 Society of Chemical Industry 相似文献
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Dimitrios G Karpouzas Allan Walker Donald S
H Drennan Robert J Froud‐Williams 《Pest management science》2001,57(1):72-81
Carbofuran was incubated in top‐soil and sub‐soil samples from a pesticide‐free site at a range of initial concentrations from 0.1 to 10 mg kg−1. Amounts of the incubated soils were removed at intervals over the subsequent 12 months, and the rate of degradation of a second carbofuran dose at 10 mg kg−1 was assessed. An applied concentration as low as 0.1 mg kg−1 to top‐soil resulted in more rapid degradation of the fresh addition of carbofuran for at least 12 months. The degree of enhancement was generally more pronounced with the higher initial concentrations. When the same study was conducted in sub‐soil samples from the same site, an initial dose of carbofuran at 0.1 mg kg−1 resulted in only small increases in rates of degradation of a second carbofuran dose. However, degradation rates in the sub‐soil samples were, in many instances, considerably greater than in the corresponding top‐soil samples, irrespective of pre‐treatment concentration or pre‐incubation period. Initial doses of 0.5 mg kg−1 and higher applied to sub‐soil successfully activated the sub‐soil microflora. Application of the VARLEACH model to simulate carbofuran movement through the soil profile indicated that approximately 0.01 mg kg−1 of carbofuran may reach a depth of 70 cm 400 days after a standard field application. The results therefore imply that adaptation of the sub‐soil microflora (c 1 m depth) by normal field rate applications of carbofuran is unlikely to occur. In experiments to investigate this in soils exposed to carbofuran in the field, there was no apparent relationship between top‐soil exposure and degradation rates in the corresponding sub‐soils. The results further confirmed that some sub‐soil samples have an inherent capacity for rapid biodegradation of carbofuran. The high levels of variability observed between replicates in some of the sub‐soil samples were attributed to the uneven distribution of a low population of carbofuran‐degrading micro‐organisms in sub‐surface soil. There was no apparent relationship between soil microbial biomass and degradation rates within or between top‐soil and sub‐soil samples. © 2001 Society of Chemical Industry 相似文献
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Fresh seeds of oilseed rape (Brassica napus) are reported to be nondormant and nonphotoblastic. However, a portion of the seeds can be induced into a light‐requiring state (secondary dormancy) for germination and also exhibit dormancy cycling. Thus, if seeds become buried in the soil they can form a persistent seedbank and become a serious volunteer weed in succeeding crops. The capacity of nondormant seeds of B. napus to be induced into secondary dormancy is contrary to results of studies on fresh nondormant seeds of some other species. A reanalysis of published and unpublished data shows that fresh seeds of this species have some degree of primary dormancy and that there is a significant relationship between primary dormancy and the capacity to enter secondary dormancy. However, most germination tests on B. napus have not been done in enough detail to detect primary dormancy (or not) in fresh seeds of this species. The usefulness of information on the relationship between primary dormancy and the capacity of the seeds to enter secondary dormancy is discussed in relation to management of weedy volunteers of this species. 相似文献
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Afonso Henrique Schaeffer Digenes Cecchin Silveira Otvio Augusto Schaeffer Nadia Canali Lngaro Leandro Vargas 《Weed Biology and Management》2021,21(1):3-10
Ryegrass (Lolium multiflorum Lam.) is one of the most difficult annual weeds to control in cultivation systems worldwide, especially in temperate regions. The widespread use of herbicides in the past two decades has selected resistant biotypes of ryegrass in crops in Southern Brazil. Ryegrass seeds are dormant when disseminated and germination can be staggered over time (crop‐growing season). Knowledge of the germination behavior of seeds from herbicide‐resistant plants has been little studied, but it would be very useful in integrated weed management. Thus, this study aimed to characterize the dynamics of the soil seed bank of two biotypes of L. multiflorum, one glyphosate‐resistant and the other glyphosate‐susceptible, under a no‐tillage system. The treatments were arranged in a bifactorial scheme, using seeds from biotypes (glyphosate‐resistant and glyphosate‐susceptible) with monthly periods of removal from field (one to 12 months). Seeds of each biotype were placed on the soil surface and covered with soil and straw to simulate no‐till conditions. The percentage of germinated, dormant, and dead seeds was evaluated every 30 days. The ryegrass seed bank of glyphosate‐susceptible and glyphosate‐resistant biotypes was reduced to 11 and 15% of dormant seeds, respectively, at the end of 12 months. However, there was no variation in germination, dormancy, and seed mortality between susceptible and glyphosate‐resistant ryegrass. Seeds of glyphosate‐resistant biotype and susceptible showed germination behavior with similar dynamics in the soil over a period of 12 months. 相似文献
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Summary Heteranthera limosa seeds were buried in flooded and in non-flooded soil and exposed to natural seasonal temperature changes in Lexington, Kentucky, USA. Seeds exhumed after various periods of burial ranging from 2 to 36 months were tested for germination under both flooded and non-flooded conditions. Seeds were dormant at maturity in September and became non-dormant during winter. Seeds buried in non-flooded soil during winter germinated to higher percentages and over a wider range of temperatures when tested under flooded conditions (in light) during spring and summer, than did those buried in flooded soil during winter. Thus, the water regime associated with rice culture (non-flooded in winter and flooded in summer) is optimal for dormancy-break and germination of H. limosa seeds. A portion of the buried seeds exhibited an annual dormancy/non-dormancy cycle, whereas others had a conditional dormancy/non-dormancy cycle. Regardless of the type of cycle, seeds buried in non-flooded soil retained the ability to germinate in light at high temperatures under flooded conditions throughout the summer. Thus, seeds potentially can germinate at any time during the growing season, whenever rice fields are flooded. Flooding fields during winter and/or sowing rice relatively early in the growing season may help in establishing rice before seeds of H. limosa germinate. 相似文献
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BACKGROUND: Enhanced atrazine degradation has been observed in agricultural soils from around the globe. Soils exhibiting enhanced atrazine degradation may be cross-adapted with other s-triazine herbicides, thereby reducing their control of sensitive weed species. The aims of this study were (1) to determine the field persistence of simazine in atrazine-adapted and non-adapted soils, (2) to compare mineralization of ring-labeled (14)C-simazine and (14)C-atrazine between atrazine-adapted and non-adapted soils and (3) to evaluate prickly sida control with simazine in atrazine-adapted and non-adapted soils.RESULTS: Pooled over two pre-emergent (PRE) application dates, simazine field persistence was 1.4-fold lower in atrazine-adapted than in non-adapted soils. For both simazine and atrazine, the mineralization lag phase was 4.3-fold shorter and the mineralization rate constant was 3.5-fold higher in atrazine-adapted than in non-adapted soils. Collectively, the persistence and mineralization data confirm cross-adaptation between these s-triazine herbicides. In non-adapted soils, simazine PRE at the 15 March and 17 April planting dates reduced prickly sida density at least 5.4-fold compared with the no simazine PRE treatment. Conversely, in atrazine-adapted soils, prickly sida densities were not statistically different between simazine PRE and no simazine PRE at either planting date, thereby indicating reduced simazine efficacy in atrazine-adapted soils.CONCLUSIONS: Results demonstrate the potential for cross-adaptation among s-triazine herbicides and the subsequent reduction in the control of otherwise sensitive weed species. Copyright (c) 2008 Society of Chemical Industry. 相似文献
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Germination is a key process in the dynamics of weed populations. In no‐tillage systems, crop seeding is often found to induce seed germination in the seeding strip. In this research, experiments to investigate options for reducing weed seedling establishment were conducted in no‐till soyabean fields located in two sites in south Brazil. A first experiment revealed that a reduction in emergence of some important weed species can be achieved by lowering seeding speed. Further experiments showed the ability of a modified seeder to contribute to an additional reduction in weed establishment. On the modified seeder, coulter discs were equipped with lateral blades, to diminish soil disturbance and to maintain a uniform soil cover by properly cutting the mulch layer. In a field with a high level of residues, the modified seeder, in contrast to the standard seeder, prevented the increase of soil exposure when seeding at high speed. The predominant weeds were annual species. Averaged over all seeding rates, the new equipment led to a 56% reduction in within‐row weed density, compared with the standard seeder. Regardless of seeder type, overall weed density increased with seeding speed, but with the modified seeder, this increase was only half that of the standard seeder. The modified seeder reduced weed biomass by 30% and increased soyabean grain yield by 42%. The research demonstrated that relatively simple changes, like a minor modification to a seeder and a lower seeding speed, can contribute to more diverse and sustainable alternatives to predominantly chemical‐oriented weed management strategies. 相似文献
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Gita Kulshrestha Shashi B Singh Shashi P Lal Nanjapur T Yaduraju 《Pest management science》2000,56(2):202-206
The effect of long‐term application of pendimethalin in a maize–wheat rotation on herbicide persistence was investigated. Pendimethalin was applied at 1.5 kg AI ha−1 separately as one or two annual applications for five consecutive years in the same plots. Residues of pendimethalin were determined by gas chromatography. Harvest‐time residues of the herbicide decreased gradually over the years and at the end of five years less than 3% of applied pendimethalin was recovered from soil as against 18% in the first year. Residues were found distributed in the soil profile up to 90 cm depth at the end of the experiment with peak distribution of 0.03 µg g−1 in the surface layer of soil treated with 10 herbicide applications. The minimum distribution was, however, in the deepest soil (75–90 cm) profile. Some of the metabolites of pendimethalin ie dealkylated pendimethalin derivative, partially reduced derivative and cyclized product were also traced in surface and sub‐surface soils up to 90 cm. A study of the rate of degradation of pendimethalin in field‐treated soils under laboratory conditions revealed faster degradation compared to control soils. Only the surface soil (0–15 cm) showed this enhanced degradation of the herbicide, which could be due to the adaptability of the aerobic micro‐organisms to degrade pendimethalin. Microbes capable of degrading herbicide were isolated, identified and pendimethalin degradation was confirmed in nutrient broth. © 2000 Society of Chemical Industry 相似文献
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It is suggested that selection for late germinating seed cohorts is significantly associated with herbicide resistance in some cropping systems. In turn, it is conceivable that rotating herbicide modes of action selects for populations with mutations for increased secondary dormancy, thus partially overcoming the delaying effect of rotation on resistance evolution. Modified seed dormancy could affect management strategies – like herbicide rotation – that are used to prevent or control herbicide resistance. Here, we review the literature for data on seed dormancy and germination dynamics of herbicide‐resistant versus susceptible plants. Few studies use plant material with similar genetic backgrounds, so there are few really comparative data. Increased dormancy and delayed germination may co‐occur with resistance to ACCase inhibitors, but there is no clear‐cut link with resistance to other herbicide classes. Population shifts are due in part to pleiotropic effects of the resistance genes, but interaction with the cropping system is also possible. We provide an example of a model simulation that accounts for genetic diversity in the dormancy trait, and subsequent consequences for various cropping systems. We strongly recommend adding more accurate and detailed mechanistic modelling to the current tools used today to predict the efficiency of prevention and management of herbicide resistance. These models should be validated through long‐term experimental designs including mono‐herbicide versus chemical rotation in the field. © 2017 Society of Chemical Industry 相似文献
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Enhanced biodegradation of ethoprophos was evident in a soil from a previously treated field in Northern Greece. However, enhanced biodegradation was specific to ethoprophos and there was no cross‐enhancement leading to rapid degradation for any of the other organophosphorus (cadusafos, fenamiphos, fonofos, isazofos) or carbamate (aldicarb, oxamyl) nematicides registered in Greece for the control of potato cyst nematodes. Studies with radio‐labelled ethoprophos showed that the adapted microflora in the soil from the previously treated field was able to degrade [propyl‐1‐14C]ethoprophos rapidly and mineralized about 60% of the initially applied nematicide. When [ethyl‐1‐14C] ethoprophos was applied, the reduction in extractable radioactivity in the previously treated soil was coupled with evolution of lower amounts of [14C] carbon dioxide and was similar to the amounts produced from the previously untreated soils. It is suggested that degradation of ethoprophos in the soil from the previously treated field proceeds via hydrolysis of the P‐S bond in the ‐S‐propyl moiety of the ethoprophos molecule, which is then further mineralized by the adapted micro‐organisms. Enhanced biodegradation of ethoprophos in this specific previously treated soil in Northern Greece and under the local environmental conditions was still evident two years after the last ethoprophos field application. It appears that, once established, enhanced biodegradation of ethoprophos can be quite stable. A possible solution to this problem might be the introduction of a rotation scheme where other nematicides like fenamiphos, cadusafos, aldicarb or oxamyl are used as alternatives with ethoprophos application restricted to only once every three or four years. © 2000 Society of Chemical Industry 相似文献
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以鱼粉、肉骨粉、豆粕、菜籽粕及芡粉等几种天然蛋白原料为底物,以碱性蛋白酶为水解酶制备出天然蛋白原料的水解物,用培养皿生物分析法检测不同蛋白原料水解物在不同浓度(0.5、1、2、5 mg/mL)条件下对杂草野菊种子的生根抑制活性。结果表明:不同蛋白原料制备出的水解物对野菊种子萌发根系生长均有抑制作用,并且随着浓度增加其抑制活性增强,不同蛋白原料水解物的除草活性有显著性差异,其除草活性顺序为:鱼粉水解物>肉骨粉水解物>豆粕水解物>菜籽粕水解物>芡粉水解物,水解物的根抑制活性与原料的蛋白含量及其水解物的多肽含量成正相关性,作者推测,天然蛋白水解物中的多肽可能是植物种子萌发时根系生长抑制活性物质,但这种根抑制活性究竟是由于特异性多肽的化感作用还是植物种子萌发时对高氮胁迫反应有待进一步研究。 相似文献
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新疆野生花卉资源植物调查及引种栽培的初步研究 总被引：9，自引：0，他引：9
本文在较全面调查的基础上介绍了新疆境内主要野生观赏资源植物的分布概况。通过前期所做的有关野生花卉种子生活力、发芽率和解除体眠等方面的实验，筛选出8种较宜引科的野生花卉植物进行引种栽培试验。最后探讨了野生花卉植物引种栽培的应用前景。 相似文献