外来杂草反枝苋对农作物的化感作用及其风险评价

利用改进的差时播种共培法,以麦田伴生恶性杂草播娘蒿为对照,在实验室条件下研究反枝苋根系分泌物及其不同浓度残枝浸提液对小麦、玉米、油菜种子萌发及生长的影响.结果显示:(1)反枝苋幼苗的根系分泌物能够显著抑制作物根长和苗高的生长;(2)反枝苋不同浓度浸提液均能抑制作物种子的萌发,其抑制作用随浓度的增加而增强;(3)除0.025 g·mL-1处理对小麦根长和苗高、玉米苗高有促进作用外,其余各浓度反枝苋浸提液对作物幼苗的根长和苗高有不同程度的抑制,且对根长的抑制作用更强;(4)反枝苋对作物幼苗的抑制作用强于恶性杂草播娘蒿,风险评估定量分析结果认定反枝苋为陕西省高度危险性植物.     

滴灌下新疆北部棉田杂草土壤种子库的时空变化

以天山北坡绿洲至沙漠边缘垂直分布的3个试验点,对比分析了漫灌和1a至4、8a的不同滴灌时间的棉田,以及不同试验点和土层深度等不同空间的杂草土壤种子库变化.结果表明,滴灌对棉田杂草种子库影响大,物种数和单位面积的种子库密度的年际间波动明显.连续滴灌改变了杂草土壤种子库的结构和组成,物种数由漫灌27种下降到1a滴灌的20种,滴灌8a后下降到15种,Shannon-Wiener多样性指数达到最低,单位面积的种子密度明显降低.随着滴灌年限的增长,狗尾草、藜、龙葵、反枝苋和凹头苋等喜旱性杂草占总种子库的比例逐渐增加,为滴灌棉田的优势杂草.狗尾草、藜、灰绿藜、龙葵、马齿苋、凹头苋、刺儿菜、黄花蒿、苦苣菜、小蓬草、荠菜、小藜、扁蓄、苘麻、田旋花、野薄荷等物种时间生态位宽度和空间生态位宽度均较大,适应较好,而虎尾草、百脉根、播娘蒿、酸模叶蓼、滨藜、野胡麻等物种生存受到明显影响.受耕作方式影响,杂草种子库主要分布于耕作层,耕作层以下46～50cm种子数最少.水平分布格局分析发现,3个地点杂草种子库的物种相似性较高,滴灌与漫灌之间种子库的物种差异要大于地理位置间的差异.     

麦秸与稻秸浸提液对油菜及2种靶标杂草种苗生长影响的差异性研究

采用室内培养皿生物测定的方法,测试不同质量浓度（0、0.02、0.03、0.05、0.08、0.10 g·mL^-1）麦秸、稻秸浸提液对油菜及油菜田2种常见靶标杂草野燕麦（Avena fatua Linn）、播娘蒿 ［Descurainia sophia（L.）Schur］种子萌发及幼苗生长的影响。结果表明,在供试质量浓度下,麦秸与稻秸浸提液对3种受体材料种苗生长的影响存在显著差异,二者对油菜种苗生长安全的最高质量浓度分别为0.08 g·mL^-1和0.05 g·mL^-1,可以用来开发研制油菜田肥料;在对油菜安全的质量浓度下,麦秸浸提液对野燕麦种苗生长无抑制作用;而稻秸浸提液对野燕麦种苗生长的抑制作用明显,可以用来开发研制油菜田防除野燕麦的生物抑草肥;在油菜的安全的质量浓度下,麦秸、稻秸浸提液对播娘蒿种苗生长均有很强的抑制作用,且麦秸的抑制作用强于稻秸,具有开发研制油菜田治理播娘蒿的生物抑草肥料的应用前景。     

苏北麦田杂草与温度关系的初步观察及其防除问题

1979—1985年,对苏北地区麦田主要恶性杂草幼苗的生态习性进行了研究,猪殃殃,麦家公,野燕麦、大巢菜等种子的最适发芽温度分别为10℃、10—15℃、15℃、20℃;种子发芽起点温度分别为1.10±0.29、-0.46±1.29、0.06±3.09和3.54±2.42℃,均低于小麦的起点发芽温度(1—2℃)。种子发芽有效积温分别为87.04±2.54(℃)、133.70±16.53(℃)、84.24±15.87(℃)和58.66±10.91(℃),均高于小麦种子发芽的有效积温(50℃)。田间调查,猪殃殃等麦田杂草出苗,幼苗生长对温度及历期的要求与播种期关系极密切,一般比小麦迟出苗1—8天,但出土后的生长势很快超过小麦,且有播期不同而分批出土为害的习性。用苯达松防除猪殃殃;用野麦畏,苯达松防除麦家公;用野麦畏、禾草灵、野燕枯防除野燕麦;用苯氧乙酸类除草剂防除大巢菜等阔叶杂草,并将其消灭在苗期阶段,可取得显著的灭草增产效果。     

细菌除草剂黄单胞菌反枝苋致病菌的筛选

从杂草反枝苋根际土壤中分离到大量的根际细菌,利用谷氨酰胺合成酶抑制剂模型和蛋白核小球藻筛选模型进行快速、高效的初筛,并结合温室盆栽复筛,筛选出一株具有较强除草活性的细菌野油菜黄单胞菌反枝苋致病变种。温室盆栽试验表明,该黄单胞菌对反枝苋、荠菜等双子叶杂草具有较强的抑制作用。      

光照强度对六种草地植物种子萌发和幼苗生长的影响

光是影响种子萌发和幼苗生长的环境因素之一, 光照强度具有日动态和季节动态, 对植物出土和光合物质积累有重要影响。通过室内控制实验, 研究松嫩草地六种植物种子萌发及幼苗生长对光照强度的响应, 对深入理解松嫩草地植物生活史早期阶段的适应策略具有重要意义。研究结果表明: 防风(Saposhnikovia divaricate)、角蒿(Incarvillea sinensis)和黄金菊(Hypochaeris grandiflora)种子萌发率不受光照强度影响, 反枝苋(Amaranthus retroflexus)、大果琉璃草(Cynoglossum divaricatum)和紫菀(Aster tataricus)在弱光或中等光照下种子萌发率最高。六种种子的萌发指数在中等光强下最大, 且与无光处理间差异显著。除大果琉璃草和反枝苋在中等光强或弱光下胚根生物量最大外, 角蒿、防风、黄金菊、紫菀均在较强光下胚根生物量最大, 无光下最小; 大果琉璃草、黄金菊、防风、反枝苋的地上生物量不受光照强度影响, 而角蒿、紫菀在较强光下地上生物量最大; 角蒿和大果琉璃草在弱光或中等光强下根冠比最大, 防风、黄金菊、紫菀、反枝苋均在较强光下根冠比最大; 萌发率和萌发指数与种子大小之间没有显著相关性, 幼苗地上和胚根生物量与种子重量成显著正相关关系。光照强度对萌发率和种子大小之间的关系无显著影响, 但胚根生物量与种子大小之间关系的斜率受到光照强度影响, 中等光强下斜率最大。因此, 中等光照条件有利于松嫩草地植物种子萌发和幼苗建植。     

牧草盲蝽危害对寄主植物体内营养物质含量及保护酶活性的影响

【目的】为了明确牧草盲蝽Lygus pratensis危害对不同寄主体内营养物质及保护酶的影响。【方法】采用分光光度法测定了牧草盲蝽偏好度不同的10种寄主植物(6种偏好寄主,偏好性依次为:灰绿藜Chenopodium glaucum马齿苋Portulaca oleracea反枝苋Amaranthus retroflexus紫花苜蓿Medicago sativa木地肤Kochia prostrata棉花Gossypium hirsutum; 4种非偏好寄主:碱蓬Suaeda glauca、天蓝苜蓿Medicago lupulina、田旋花Convolvulus arvensis和宽叶独行菜Lepidium latifolium)受其危害后叶片中叶绿素、可溶性糖和氨基酸含量以及保护酶活性。【结果】结果表明,受牧草盲蝽为害后,不同寄主植物叶片叶绿素含量均有所下降,其中反枝苋叶片叶绿素含量下降率最低,仅2.6%;紫花苜蓿叶片叶绿素含量下降率最高,达26.21%。可溶性糖含量变化各异,木地肤叶片可溶性糖含量下降率最高,达24.05%,且与对照(未受害株)间存在显著差异;灰绿藜叶片可溶性糖含量上升68.92%,与对照差异极显著。除反枝苋叶片游离脯氨酸含量下降38.87%,其余寄主叶片中游离脯氨酸含量均呈上升趋势。各寄主植物叶片中蛋白质含量均有所下降,反枝苋中下降率最低,仅2.96%。不同寄主中受害后叶片POD活性均呈增强趋势,马齿苋受害后叶片POD活性增幅最高,达74.23%。受害后寄主叶片CAT活性有增有减,灰绿藜、紫花苜蓿和田旋花叶片CAT活性增高,分别增加45.07%,30.95%和22.47%;马齿苋与天蓝苜蓿受害后叶片CAT活性下降显著。反枝苋、天蓝苜蓿受害后叶片SOD活性下降,其余寄主叶片中SOD活性上升,但均无显著差异。【结论】寄主受害后,叶片叶绿素含量、游离脯氨酸含量变化与牧草盲蝽偏好性具有较好的相关性,而可溶性糖和蛋白质含量及保护酶活性变化无规律性或无显著差异。     

新疆荒漠地区盐生植物灰绿藜种子的萌发特性及其对生境的适应性

研究新疆地区广泛分布的一年生盐生植物灰绿藜种子的萌发特性及其对生境适应性的结果表明：（1）灰绿藜种子萌发的温度范围较广,在15-45℃范围内均有50％以上的种子可以正常萌发,其对高温的耐受力较强,对光不敏感;（2）在一定浓度的聚乙二醇（PEG6000）范围内（≤25％）,PEG引起的渗透胁迫对灰绿藜种子萌发的抑制作用较小,但随着PEG浓度的加大其戍苗率逐渐下降;（3）灰绿藜种子在萌发时有较高的耐盐性,NaCl和KCl浓度达到400mmol．L^-1时种子的萌发率仍在90％以上;盐对灰绿藜种子萌发的抑制作用主要表现为种子萌发时间的延迟：低浓度的NaCl和KCl对灰绿藜幼苗生长均有促进作用,子叶生长状态明显改善,胚轴的生长也受到促进。     

12种有毒植物的化感效应比较研究

以油菜、燕麦、反枝苋和狗尾草为受体,采用室内生物测定法和盆栽法,研究了甘肃天祝天然草地12种有毒植物的化感作用.结果表明:离体条件下,黄花棘豆、臭蒿、节烈角茴香和露蕊乌头植株水浸液对4种受体植物化感作用较强,其综合化感效应值(M)分别为-0.781 5、-0.685 9、-0.667 0和-0.643 2;其次是密花香薷、醉马草、美丽凤毛菊、甘肃马先蒿、迷果芹和异叶青兰,其M值均低于-0.4;对受体植物化感作用较弱的是乳白香青(M值为-0.343 9)和铁棒锤(M值为-0.262 5).黄花棘豆植株对盆栽的油菜、燕麦、反枝苋和狗尾草幼苗生长有较强的抑制作用,综合化感效应M值分别为-0.529 6、-0.356 2、-0.520 1和-0.588 4.可见黄花棘豆表现出较强的化感作用,具有一定的开发利用价值.     

外来入侵杂草反枝苋的研究进展

反枝苋(Amaranthus retroflexus)原产于美洲,是广泛分布于我国的外来入侵杂草。本文就反枝苋的种子生物学特性、化感作用、表型可塑性、作为典型C4植物的生理生态特征、其与作物的竞争机制、在我国的入侵扩散过程及影响因子,以及其对增强紫外线辐射的生理生态响应和防除方法分别进行了评述。结果表明:反枝苋的一些生物学特性对其入侵成功具有重要作用,其种子数量大、种子萌发温度范围广、表型可塑性强、光合能力强、并可通过化感作用影响多种作物的生长,温度和湿度适应范围广,可以入侵多种生境类型。针对目前研究中的不足,应加强以下方面的研究:1)反枝苋对大范围环境梯度变化的适应机制;2)反枝苋对农田生态系统资源波动的响应;3)反枝苋的化感作用机制;4)反枝苋的综合控制技术。     

60Co-γ辐照对越南油茶种子发芽及幼苗形态指标的影响

为了研究⁶⁰Co-γ辐照对越南油茶Camellia drupifera种子发芽和表观形态指标的影响,选取越南油茶璠龙3号‘Fanglong 3’和璠龙5号‘Fanglong 5’种子分别进行0、40 Gy、50 Gy、60 Gy、70 Gy ⁶⁰Co-γ辐照并测定种子发芽率和出苗率以及幼苗生长表观形态指标(苗高、地径、叶长、叶宽、叶面积)。结果表明,⁶⁰Co-γ辐照对越南油茶种子发芽率影响小,对其出苗率、苗高、地径以及叶片生长有明显抑制作用,尤其是高剂量(60 Gy、70 Gy)辐照对越南油茶种子损伤较大,严重影响其出苗及幼苗生长。高剂量辐照明显延迟越南油茶的出苗时间,抑制幼苗生长,导致苗木瘦弱、生长缓慢,植株呈现矮化现象。高剂量亦抑制越南油茶叶片生长,导致叶片瘦小,生长缓慢。璠龙3号种子⁶⁰Co-γ辐照半致死剂量为64 Gy,璠龙5号为57 Gy。     

Changes in sensitivity of Amaranthus retroflexus L seeds to ethylene during preincubation. II. Effects of alternating temperature and burial in soil

Abstract. The effects of diurnally alternating temperatures and of prolonged burial in the soil on germination response of redroot pigweed ( Amaranthus retroflexus L.) seeds to ethylene were investigated. Percentage germination in a 12 h/12 h, 23° C/35° C temperature regime roughly equalled that observed at constant 35° C, and greatly exceeded that observed at 30°C. Preincubation for 61 d in alternating temperatures, which were gradually increased to simulate soil warming in spring, caused little germination in the absence of ethylene, but considerably enhanced sensitivity to ethylene. Seeds kept in soil in the same temperature regime failed to show the response to ethylene, and the soil itself removed ethylene from the soil atmosphere.
After burial in a field plot either over winter or during the summer, seeds had a very low ethylene response threshold (0.01−0.05 cm³ m⁻³) and strong response to ethylene (70–95% germination at 51 cm³ m⁻³ compared to 1–20% without ethylene). Germinability of seeds buried overwinter declined between 10 May (85%) and 24 May (7%), and 90% of those recovered on or after 24 May had a visible rupture in the seed coat. Apparently, germination had begun during burial, but was arrested by unknown causes in an early phase and was followed by seed deterioration.
Although the role of ethylene in germination of buried seeds remains uncertain, the greatly enhanced sensitivity to ethylene observed in pigweed seeds after burial deserves further investigation.     

Inhibitory effects of monoterpenes on seed germination and seedling growth

Monoterpenes, the chemical constituents of essential oils found in plants, are known biologically active compounds. The present study was conducted to investigate the inhibitory effects of 30 monoterpenes including monoterpene hydrocarbons and oxygenated monoterpenes on seed germination and seedling growth of Amaranthus retroflexus, Chenopodium album and Rumex crispus under laboratory conditions. The monoterpenes were applied at contents of 10 and 20 microl for liquid compounds and 10 and 20 microg for solid compounds. The results show that most of the monoterpenes significantly inhibited seed germination and seedling growth of the tested plants. Oxygenated monoterpenes including beta-citronellol, nerol and terpinen-4-ol completely inhibited seed germination and seedling growth of all tested plants. Their inhibitory effects were also stronger than that of the herbicide 2,4-D. In general, monoterpenes were less effective against seed germination and seedling growth of C. album as compared with R. crispus and A. retroflexus. Phytotoxic effects of monoterpene hydrocarbons were found to be lower than those of oxygenated monoterpenes. The alcohol derivatives of oxygenated monoterpenes were also found to be more phytotoxic as compared with their acetate derivatives. Based on the present results, it can be concluded that the oxygenated monoterpenes can be used as potential bio-herbicides.     

Temperature control of germination and its possible role in the survival of a non-dormant population of Avena fatua

Germination of freshly harvested seeds of a non-dormant (ND) line (Stonehouse 319) of wild oats ( Avena fatua L.) was inhibited by incubation of the seeds at relatively high temperatures of 25 and 30°C. The germination inhibition in these seeds appeared to be a case of thermo-inhibition which was the direct effect of hightemperature treatment (HIT), since it did not persist after transferring the seeds to an optimum germination temperature of 20°C. Even a prolonged HTT of 30°C for over 5 weeks did not prevent germination of about 80% of the seeds transferred to 20°C. However, in a significant proportion of the seeds, thermo-dormancy was induced by 10 days of HTT at 30°C if the seeds were then incubated at sub-optimal temperatures of 5 to 15°C. This thermo-dormancy would appear to be 'restrictive' in form, since its expression was restricted to very specific conditions. Relatively low inclubation temperaturs of 5 and 10°C markedly slowed germination whether HTT was applied or not. The results suggest that thermo-inhibition and thermo-dormancy, induced during seasonal temperature fluctuations, may provide a survival mechanism for seeds of such ND lines as Stonehouse 319.     

Germination responses of a non-dormant seed population of Amaranthus patulus Bertol. to constant temperatures in the sub-optimal range

Abstract. The germination responses of a nondormant seed population of Amaranthus patulus Bertol, at constant sub-optimal temperatures in the range of 10–34°C were analysed through a detailed time-course study. Although a final germination percentage of nearly 100% was attained at temperatures above 18°C, it fell abruptly to zero with decreasing temperature from 17 to 10°C. The final germination percentage, v. temperature plotted on a normal probability scale yielded a straight line, indicating normality of the lower limit temperature within seed population with an estimated mean of 13.75°C and a standard deviation of 1.50°C. Simple linear relationships were obtained between the temperature and the germination rates, i.e., the reciprocals of the time taken to germinate by the subpopulations with 20–80% germination. The linear relationships were characterized by similar base temperatures or theoretical limit temperatures of about 11°C but there was a variation in the required 'thermal times' (θ), the distribution of which could be approximated for the seed population by the following distribution function: where m is the median of the distribution and A is a parameter characterizing the pattern of the distribution. When the germination rates were calculated after subtracting 10–14 h from the time actually consumed in germination, linear Arrhenius relationships were obtained. The apparent activation energy estimated from the linear regression of Arrhenius plot was approximately 100 kJ mol⁻¹ with all 20–80% subpopulations.     

Uptake and Fate of Ethephon ([2-Chloroethyl]phosphonic Acid) in Dormant Weed Seeds

Although ethephon ([2-chloroethyl]phosphonic acid) is often used as a form of liquid ethylene in studies of seed germination, it is not known if ethylene evolved from ethephon in the seed is sufficient to elicit the desired response and/or if ethephon has a regulatory action that alone accounts for the response. For these reasons we studied the uptake and fate of [1,2-¹⁴C]ethephon in dormant seeds of Avena fatua, Sinapis arvensis, Thlaspi arvense, and Chenopodium album. The radioactivity within the seeds was separated into a labile carbon-labeled ethephon/ethylene fraction (64-87%) and, following extraction in methanol-chloroform-water (12:5:3), into fractions associated with insoluble (12-29%) and soluble (3-8%) seed constituents. The radioactivity associated with seed constituents was reduced 5 to 75% by hot alkaline hydrolysis (2.5 n KOH, 70° C for 1 hour). Although a small portion of the ethephon (or metabolite of ethephon/ethylene) taken up by the seeds is tightly bound to the tissues, our results indicate that, at the appropriate external concentrations of ethephon, the amount of ethylene evolved from ethephon within the seeds is sufficient to produce the desired ethylene mediated responses. However, factors affecting the decomposition of ethephon must be considered in the decision as to whether to use ethephon as a liquid supply of ethylene.     

子莲新品种‘武植子莲1号’和‘武植子莲2号’产量与营养品质分析

对子莲（Nelumbo nucifera Gaertn.）新品种‘武植子莲1号’和‘武植子莲2号’与其他12个主栽子莲品种的莲子产量和品质性状进行分析,并通过隶属函数分析法对他们的营养品质性状进行综合评价。结果显示：不同子莲品种的产量和营养品质性状差异显著,同一品种在不同发育时期莲子的可溶性糖和淀粉含量等营养指标差异较大;鲜莲子的可溶性糖含量显著高于成熟莲子,而蛋白质和淀粉含量显著低于成熟莲子。与12个主栽子莲品种相比,‘武植子莲1号’在产量上较为突出,成熟莲子的淀粉含量达52.15%,是生产天然淀粉的优良品种;‘武植子莲2号’鲜莲子的直链淀粉和支链淀粉含量低,可溶性糖含量达23.43%,适合鲜食。隶属函数分析结果表明,‘武植子莲1号’和‘武植子莲2号’的综合营养品质较好,具有很高的应用价值。     

盐胁迫对不同品种小白菜种子萌发特性的影响

采用5个小白菜(Brassica chinensis)品种(‘七宝青’、‘夏冬青’、‘四月慢’、‘南京中杆’和‘605’),用100 mmol/L NaCl对种子发芽作盐胁迫处理,从发芽势、发芽率、发芽指数、盐害指数、胚长和胚鲜重等指标比较了5个小白菜品种的抗盐性。结果表明,‘七宝青’种子的耐盐性优于其它品种。     

The physiological basis of seed dormancy in Avena fatua. IX. Characterization of two dormancy states

The dormancy-breaking effect of several known germination promoters was studied in 9 genetically pure lines of Avena fatua L. during a period of controlled after-ripening. Changes in the germination response show at least two dormancy states in the caryopses of these lines. The first state is overcome by a short period of after-ripening and is insensitive to nitrate and azide, while the second state is more persistent and is sensitive to nitrate and azide. Both states are sensitive to gibberellic acid (OA,) and ethanol. In the most dormant lines a third ethanol-insensitive dormancy state is present. The duration of both major dormancy states was related to several environmental factors influencing plant growth and seed storage. Duration was increased in caryopses produced from plants matured under low temperatures (15°C) and decreased in caryopses produced from plants matured under high temperatures (25°C). Duration was increased in caryopses after-ripened under low temperatures (4°C) and decreased in caryopses after-ripened under high temperatures (45°C). Dehulling the seeds prior to after-ripening reduced the duration of both major dormancy states. The multiple state dormancy system and its environmentally induced plasticity are discussed with reference to previous explanations of the dormancy mechanism in wild oats.