龙葵种子休眠解除方法研究

龙葵种子具有休眠习性,采用合适的化学药剂能够打破龙葵种子休眠。H2O2、NaOH、HCl、KNO3、GA浸泡24 h,均能明显提高龙葵种子的萌发率。以2.25～36.00 g/L HCl浸种的萌发率最高,萌发率超过90.00%;40.00 g/L KNO3与200.00 mg/L GA浸种后,萌发率超过80.00%,已达到打破龙葵种子的休眠的目的。     

不同温度、水热条件对3种植物种子物理休眠解除的影响

研究种子物理休眠解除机制及其影响因素是了解种子休眠生态学和种群适应策略的重要途径。准噶尔无叶豆(Eremosparton songoricum)、银沙槐(Ammodendron bifolium)和乌拉尔甘草(Glycyrrhiza uralensis)是在干旱区分布的3种豆科珍稀物种,其种子均存在物理休眠现象。以3种植物种子为研究对象,探讨冷层积(5℃)、夏季高温及干/湿处理对种子物理休眠解除的作用。研究表明:1 3种植物种子的硬实率高,种皮透水性低,划破种皮的处理方法可有效解除3种植物种子的物理休眠。2冷层积对3种植物种子的物理休眠解除无显著影响。3高温、干/湿条件和处理时间显著影响3种植物种子的萌发率,其中,湿热条件更能有效解除3种植物种子的物理休眠。准噶尔无叶豆和银沙槐种子的物理休眠解除率与温度呈正相关,在80℃和65℃湿热条件下其萌发率最高,分别达到(70.48±2.92)%和(78.13±3.67)%,而乌拉尔甘草种子的物理休眠解除率与温度呈负相关,40℃湿热条件下的萌发率最高,达到(85.23±3.82)%。表明荒漠地区夏季的极端高温有利于种子物理休眠的解除,但较少的降水量却限制了种子的萌发,这可能是导致该地区3种植物自然种群实生苗稀少,有性更新弱的主要原因之一。     

刺萼龙葵种子休眠和萌发特性研究进展

刺萼龙葵是一种外来恶性杂草,在我国境内的传播对现有的生态系统构成严重威胁。刺萼龙葵对环境条件的广泛适应能力增强了其竞争优势,使其发展成为一种高度危险的外来入侵杂草,控制刺萼龙葵的危害和扩散蔓延已变得越来越重要。文章综述了刺萼龙葵种子的形态特征和休眠机制,总结了种子萌发特性和打破种子休眠的一些方法,为制订其综合防控策略提供科学依据。     

野老鹳草Geranium carolinianum种子的萌发条件

为明确野老鹳草Geranium carolinianum种子的休眠特性及萌发适宜的环境条件，采用培养皿法和盆钵法研究野老鹳草种子萌发和出苗适宜的条件，记录种子萌发数，计算种子萌发率、平均萌发时间及萌发指数。结果显示，野老鹳草具有较长的休眠期，新采集的野老鹳草种子在室温干储210 d后可以解除休眠；在10~25℃的恒温条件下种子萌发率均在93.8%以上；有无光照及光周期的长短对种子的萌发无影响；对酸碱度不敏感，在pH 4~10范围内种子萌发率均在91.3%以上；对水势具有一定耐受力，抑制50%种子萌发率所需的水势为-0.42 MPa；盐分对野老鹳草种子萌发具有一定抑制作用，当盐浓度达到160 mmol/L时基本不能萌发；此外，种子在土壤垂直深度5 cm以内时仍然可以出苗，对播种深度适应性较强。表明野老鹳草种子具有较长休眠期，土壤层积可解除种子休眠；而且野老鹳草种子对温度、光照、土壤酸碱度、播种深度适应性较强，水势及盐分对种子萌发有一定影响。     

苘麻不同种群的种子萌发特性

为揭示农田恶性杂草苘麻种子的休眠萌发机制, 探寻基于休眠调控的绿色防控途径, 采用60℃温水浸种30 min+30℃恒温培养的方法测定了不同种群苘麻 Abutilon theophrasti 种子的萌发率?萌发势与萌发指数?结果表明, 供试的18个种群中, 种群XJ01?JL04和JL01的萌发率分别为89.95%?89.18%和87.77%, 显著高于其他种群; 而种群HB01的萌发率最低, 仅为41.50%?测定了萌发差异较大的种群JL01和HB01种子的萌发关键期指标, 发现JL01种群在温水浸种后培养2 h的吸胀数量?10 h破皮数量和20 h露白数量, 显著高于HB01种群, 其种子数量分别是HB01种群的1.37?1.76和2.96倍?通过进一步比较8个种群种子的萌发吸胀?破皮与露白数量指标, 证实苘麻不同种群种子存在显著休眠萌发差异, 其原因可能是由于母体生活环境不同所致?     

外来有害植物土荆芥种子贮藏与萌发特性的研究

研究了不同光照和温度对外来有害植物土荆芥（Chenopodium ambrosioides L．）种子萌发率的影响及种子在不同贮藏时间和不同贮藏温度下萌发率的变化。结果表明，光照是土荆芥种子萌发的必要条件，全黑暗条件下萌发率仅为9．7％。种子在15～20℃恒温条件下萌发率均达到80％以上，25℃恒温和10℃恒温能显著抑制其萌发。零下低温（-20℃）和零上低温（4℃）贮藏3个月的土荆芥种子萌发率分别为86．3％和84．7％，与贮藏前萌发率（89．3％）相比无显著差异，而在室温和25℃条件下贮藏的种子，萌发率显著下降。     

不同贮藏条件对大赖草种子萌发的影响

将野外观测与室内实验相结合,研究不同贮藏条件对大赖草种子萌发的影响。结果表明：室内干藏与野外埋藏于地表的种子随贮藏时间的延长,种子萌发率呈现缓慢升高后逐渐降低的趋势,说明大赖草种子存在着后熟现象;埋藏5 cm深度的种子,埋藏2、7、8个月时,种子自然萌发率分别为5.15%、7.52%和94%,剩余种子在室内条件下萌发率大于95%。而埋藏于原生境的种子埋藏2个月无萌发现象,埋藏8个月自然萌发率为90%;说明大赖草的种子在土壤中属于瞬间种子库;黑暗有利于大赖草种子的萌发。不同贮藏条件下大赖草种子的含水量表现为：埋藏5 cm深度>埋藏于地表>室内干藏,大赖草种子萌发的最低含水量为19.5%。在自然生境中,野外埋藏的种子被动物搬运的占12%～90%,平均达44.5%,致使土壤中种子数量锐减。因此,大赖草种子在土壤种子库中数量匮乏;自然生境中干旱少雨、水分缺少,导致种子萌发后易“闪苗”。这些因素是大赖草有性繁殖更新率低的主要原因。     

龙葵果实汁液的除草活性初探

以龙葵(Solanum nigrum L.)、反枝苋(Amaranthus retroflexus L.)为试材,用种子萌发法检测了龙葵果实汁液对其萌发的抑制作用.试验结果证明,龙葵果实汁液中含有除草活性物质,而且活性较高,热稳定性较好,在150 ℃下加热0.5 h依然保持除草活性.龙葵果实汁液对龙葵种子萌发的抑制作用高于对反枝苋的抑制作用.水培14 d,龙葵果实汁液含量为1%时,只能推迟龙葵种子的萌发时间,对最终的发芽率没有影响;含量为5%时,龙葵种子的发芽率仅为的21.5%;含量为10%时能够完全抑制龙葵种子的萌发.含量低于5%时,对反枝苋种子萌没有影响;含量为10%、15%、20%时,反枝苋的发芽率分别为60.00%、43.75%、22.50%.     

温周期、贮藏时间和盐分对短毛柽柳种子萌发的影响

短毛柽柳(Tamarix karelinii)是分布于盐渍化沙地和重盐碱地的灌木。为了阐明短毛柽柳种子的萌发特性,设置不同的温周期、储藏时间和盐分梯度,采用室内控制实验研究这些因子对种子萌发的影响。结果表明:1短毛柽柳种子在4个温周期中均具有高的萌发率,并且温周期温度越高,种子的萌发速率越快。2室温贮藏1个月显著提高种子的萌发速率,在贮藏6个月内,种子的最终萌发率都能达到100%。3≤0.8 mol·L~(-1)的Na Cl溶液对种子的最终萌发率无显著影响,而≥1.0 mol·L~(-1)的溶液则抑制种子的萌发,且随着浓度的增加,种子的最终萌发率呈下降趋势,直至为0。将1.0~4.0 mol·L~(-1)溶液中没有萌发的种子,转移至蒸馏水继续培养后,仍有71.67%~28.00%的种子恢复萌发率,表明种子具有较强的耐盐性。对短毛柽柳种子萌发特性的研究,为短毛柽柳的种苗培育提供基础资料。     

喜盐鸢尾种子休眠与萌发特性初步研究

喜盐鸢尾(Iris halophila）是一种干旱地区野生观赏花卉,种子萌发困难,限制了该种在园林绿化中的应用,也为育种工作带来难度。从吸水性和萌发性两个方面对喜盐鸢尾种子休眠原因和打破休眠的方法进行了探索。研究表明,在25/10 ℃（高温/低温）条件下,喜盐鸢尾种子萌发率最高,达到44.33%;胚乳中的萌发抑制物质是限制喜盐鸢尾种子萌发的主要原因;种皮可限制胚乳萌发抑制物质的释放。砂纸摩擦、切除部分胚乳和赤霉素(GA3)处理都能提高种子的萌发率。综合考虑经济费用和可操作性等因素,砂纸摩擦后蒸馏水浸种处理是打破喜盐鸢尾种子萌发行之有效的方法。     

Seasonal changes in seed dormancy of Solanum nigrum and Solanum physalifolium

The seed dormancy cycle in Solanum nigrum and Solanum physalifolium was studied in relation to seasonal temperature. Seed lots of both species were buried in pots outdoors in a randomised complete block design with four replicates from November 2004 to November 2006. At regular intervals, samples of the seeds were randomly exhumed and tested for germination in incubators at three temperatures and light/darkness regimes. For both species, low winter temperature weakened dormancy and high temperature strengthened it. Dormancy induction mainly occurred from August to October in both species after experiencing warm temperatures. An exception from the general pattern of seed dormancy was however observed; seed germination percentages were temporarily reduced in early spring, followed by a peak in germination, before the main period of strong dormancy in S. nigrum . The same phenomenon was observed in S. physalifolium during June in the first year. This short-lived dormancy induction might explain the late emergence of the species. Seed dormancy enables the species to maximise its chance of survival by regulating germination timing to favourable conditions. Therefore, information on the dormancy cycle can be used to predict seedling emergence and optimise weed control operations.     

Seasonal changes in the germination of buried seeds of Monochoria vaginalis

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.     

Germination characteristics of Amaranthus quitensis as affected by seed production date and duration of burial

Thermal requirements for the germination of Amaranthus quitensis, a common annual weed in Argentina, were studied. In addition, temporal changes in dormancy from seeds produced at different times during the growing season were examined. For this second objective, thermal and light requirements for germination were tested in seeds buried at different depths, with or without crop residues. Base and optimum temperatures for germination rates were 12.8°C and 37°C respectively. At dispersal time, maximum percentage germination was 60–70% and this was generally recorded at 35°C/25°C in a 14-h photoperiod. Seed germination tended to increase in later seed collection dates. Seeds of A. quitensis showed seasonal changes in germinability in the soil. In winter, germination of retrieved seeds increased to over 90% until summer, after which there was a decrease until the following winter when germination was close to 40%. There were no differences in germinability between burial depths and crop residue levels. Germination requirements for alternating temperatures and light tended to disappear after burial. Initial viability was 99% and declined slightly during burial. Soil temperature seems to play a crucial role not only by regulating seasonal changes in dormancy, but also by defining the percentage and the germination rate in non-dormant seeds.     

Seed dormancy dynamics and germination characteristics of Solanum nigrum

Four experiments were conducted to study seed dormancy and germination requirements in Solanum nigrum . In Expt 1, seeds were stratified at different constant and stepwise rising temperatures and their germinability was tested at three germination regimes at weekly intervals. In Expts 2–4, seeds dry stored at 4°C and stratified at 5 and 15°C were tested at constant temperatures, as well as fluctuating temperatures with constant and increasing amplitudes. Results suggest that the rate of dormancy release increased with increasing temperatures ranging from 4.5 to 18.6°C. However, prolonged stratification at higher temperatures caused subsequent induction of dormancy. When tested at constant temperatures, stratified seeds germinated between 18 and 34°C, with the optimum between 26 and 30°C, while dry-stored seeds showed no germination. Fluctuating temperatures, with amplitudes ranging from 5 to 15°C, promoted germination of seeds from all treatments. The dormancy dynamics and germination characteristics of the species will have implications for its survival and establishment. This information can be used to predict time of emergence and, thus, improve control of the species in weed management systems.     

Annual cycles of germinability and differences between primary and secondary dormancy in buried seeds of Echinochloa crus-galli

The seasonal changes in percentage of dormant seeds of Echinochloa crus-galli in the field were recorded for 4 years. The lots of seeds were wrapped in nylon fabric, buried 20 cm under the grass sward and exhumed at monthly intervals. The proportion of seeds germinating under light conditions at a constant temperature of 25 °C fluctuated between 0% and 96%, with maxima in May–July and minima in September–November. Small between-year differences in the course of summer dormancy induction and its winter termination were probably caused by variation of weather conditions.
Attributes of dormancy innate to seeds after maturation (primary dormancy) and dormancy induced in buried seeds during the summer (secondary dormancy) were compared by investigating the rate of dormancy termination during storage of (a) dry seeds at 25 °C, (b) imbibed seeds at 5°C and (c) in seeds buried under field conditions during October–June. Percentage of germination increased faster in secondary than primary dormant seeds at both constant 25 °C and 5 °C. The seeds with primary and secondary dormancy also differed in the response to `germination pre-treatment', a 10-day exposure of imbibed seeds at 25 °C that causes germination of the non-dormant fraction of seed materials. After this treatment the time to resuming germination in primary dormant seeds was substantially increased, whereas the secondary dormant seeds were much less affected. Annual variation in the proportion of germinable seeds explains the low efficiency of autumn soil cultivation for decreasing reserves of E. crus-galli seeds in the soil.     

The roles of light and pericarp on seed dormancy and germination in feral Raphanus sativus (Brassicaceae)

The timing of seed germination may determine the success of a weed species in an agroecosystem, and its expression is modulated by environmental conditions, but also by seed physiology and anatomy. The aims of this study were to investigate the roles of light, pericarp, dry storage and cold stratification on seed dormancy and germination in feral radish, a troublesome agricultural weed in temperate zones of the Americas that reduces crop yields. To this end, we used isolated intact pods and extracted seeds to test germination over time under contrasting temperature, light and storage conditions. Here, we showed that fresh seeds were non‐dormant, but that light and the presence of the pericarp reduced germination, especially under low temperatures. The pericarp reduced the final water content absorbed by seeds inside pods and decreased absorption/dehydration rates. The pericarp showed several small lignified cell layers in the endocarp, and x‐ray images displayed the lack of space between the partially embedded seed and the endocarp. Dry storage and cold stratification were ineffective in breaking the dormancy imposed by the pericarp. The apparent requirement for darkness and the mechanical restriction of the pericarp may have the potential to induce dormancy, spreading the timing of seed germination over a more extended period and hindering the control of feral radish.     

Seasonal changes in germination responses of buried seeds of the weedy summer annual grass Setaria glauca

Seeds of Setaria glauca (L.) Beauv. buried in soil and exposed to natural temperature cycles exhibited seasonal changes in temperature, but generally not light; dark requirements for germination. Seeds were dormant at maturity in late September and October (autumn), and during burial from October to January they entered conditional dormancy, germinating up to ≥60% in light and darkness at daily thermoperiods of 25/15,30/15 and 35/20^C by January. During burial from February to May or June, seeds became non-dormant and germinated up to 68–100% in light and darkness at 15/6,20/10,25/15,30/15 and 35/20^C in May or June. At maximum yearly temperatures in June or July–August, 65–89% of the seeds entered conditional dormancy (germinating at 30/15 and 35/20, but not at 15/6,20/10 and 25/15^C), and the others entered dormancy (not germinating at any thermoperiod). Thus, most buried seeds had an annual conditional dormancy/non-dormancy cycle, but some had an annual dormancy/non-dormancy cycle. Except for seeds buried in 1990 that lost the ability to germinate in darkness at all thermoperiods the first summer of burial, seeds incubated in light and in darkness exhibited the same patterns of seasonal changes in germination responses. Although conditionally dormant and non-dormant seeds germinated to high percentages in darkness in Petri dishes, seedlings were found only in bags of seeds exhumed in April and May 1983, indicating that some factor(s) associated with the burial environment other than darkness prevented germination of buried seeds.     

A quantitative analysis of temperature-dependent dormancy changes in Polygonum aviculare seeds

Mathematical models that predict emergence of weed seedbanks could be useful tools for determining the most suitable time for weed seedling control and, consequently, should result in a higher efficacy of applied control methods. To achieve this goal in dormant weed species, functional relationships should be established between environmental factors regulating dormancy and dormancy changes of seed populations. In the present work, we used a simple model and an optimisation procedure to quantify the effect of temperature on Polygonum aviculare seed dormancy release and induction, based on germination data. Dormancy release rate was inversely related to temperature, showing a decreasing logistic trend that results in no dormancy release for seeds exposed to 20 and 25°C. In contrast, dormancy induction rates in absolute values were positively associated with temperature, showing a logistic trend in which dormancy induction was almost zero at low temperatures and maximal at 25°C. Derived model parameters were used to simulate dormancy changes of P. aviculare seeds stored under controlled and field conditions. These results suggest that similar model structures could be used to quantify temperature effects on seed dormancy status of other weed species and to develop predictive models of weed emergence.     

Dormancy,germination and emergence of Urochloa panicoides regulated by temperature

Urochloa panicoides is an annual weed of summer crops. In Argentina, in subhumid areas with monsoon rainfall, it germinates and establishes in a single flush. To (i) identify the environmental factors that modify its seed dormancy level and germination and (ii) quantify the parameters describing the thermal behaviour of the germination and emergence dynamics of this weed under non‐limiting water conditions, we established a set of germination experiments performed (i) under controlled conditions using seeds after ripened for 3 or 6 months in different thermal and hydric conditions and (ii) under field conditions, where the soil temperature was modified by applying different shading levels. Seed dormancy level remained high with 3 months after ripening in all treatments. After 6 months, seeds stored at 4°C in dry conditions did not germinate at any temperature, while seeds stored at 25°C in dry conditions and in situ germinated c. 20% and 60% respectively. Germination percentage was higher in seeds harvested before their natural dispersal. The base, optimum and maximum temperatures for seed germination were 6, 35 and 45°C respectively. Shading reduced the number of emerged seedlings, possibly by reducing the soil thermal amplitude. The results explained the dormancy‐breaking mechanism of U. panicoides that allows a high germination rate in the field when rainfall occurs.     

Seed dormancy and periodicity of seedling emergence in Veronica hederifolia L.

Emergence of Veronica hederifolia seedlings began in mid-October and continued into spring; few appeared from June to September. Ripe seeds shed in June were dormant but wben buried in soil outdoors developed a capacity for germination initially at low temperatures (constant4 C; daily alternations of 4-10° and 4-1 5 C) and later at somewhat higher temperatures, with peak germination in September-November. During winter, spring and early summer thc germination capacity declined, to increase again in late summer and early autumn. Cyclic physiological changes thus occur in seeds of V,hederifolia present in the soil, with which lhe consistent seasonal periodicity of seedling emergence is associated. In dry storage ihe capacity for germination progressively increased, but alter 12 months there was a sharp decline in germination at 4° C. Few seeds germinated at 20° C, but moistening with GA 4/7; brought about complete germination at this temperature.