不同培养条件下萼花臂尾轮虫休眠卵的萌发

为确定萼花臂尾轮虫休眠卵的最适形成条件 ,或为提高特定培养条件下形成的休眠卵的萌发率 ,对不同温度、食物、光照和 pH条件下萼花臂尾轮虫形成的休眠卵进行了萌发研究。发现不同培养条件下形成的休眠卵在不同萌发条件下的萌发历时均为实验开始后的第 1～ 7天 ,萌发率高峰均出现在第 1～ 3天。在萌发温度为15℃～ 30℃范围内 ,2 0℃下形成的休眠卵在 2 0℃的萌发温度下累积萌发率最高 ,为 5 2 5 0± 6 89% ;母体以小球藻为食物时 ,其所产休眠卵的平均累积萌发率为 2 7 92 % ,显著大于以斜生栅藻或蛋白核小球藻和斜生栅藻所组成的混合藻为食物时 ;休眠卵形成和萌发时的光照条件对其累积萌发率无显著的影响 ;pH6 5和 7 5条件下形成的休眠卵的累积萌发率较高 ,分别为 32 5 0± 7 0 7%和 38 75± 15 5 3%。本研究和已报道的研究结果表明 :不同培养条件下形成的休眠卵在不同条件下萌发时均呈同步萌发型式 ;2 0℃和pH7 5分别是武汉东湖萼花臂尾轮虫休眠卵形成的最适温度和最适 pH条件。     

乌蕨孢子萌发研究

用随机区组试验和方差分析方法, 研究了培养温度、贮藏温度、GA 处理和光照强度对乌蕨( Sphenomeris chinensis) 孢子萌发的影响。与室温(20～25℃ ) 相比, 培养温度在28℃时, 孢子最大萌发率相近而萌发速率明显较高。贮藏温度(A) 极显著( P < 0 . 01 ) 影响孢子萌发率, - 20℃ 贮藏降低萌发率; GA (B) 对孢子萌发率无显著影响。光照强度(C) 极显著( P < 0.01) 影响孢子萌发率, 充足光照和弱光照无显著差异, 黑暗处理降低萌发率。A×B, A×C, B×C 及A×B×C 交互效应不显著。     

苍耳柄锈菌三裂叶豚草专化型冬孢子萌发过程及萌发条件的研究

本文采用光学显微镜和扫描电子显微镜技术及荧光染色技术,对苍耳柄锈菌三裂叶豚草专化型Puccinia xanthii sp.ambrosiae-trifidae冬孢子的萌发过程和萌发条件进行了研究。结果表明:冬孢子堆成熟时突破寄主表皮外露;在寄主上冬孢子萌发时由上细胞顶部出现皱褶和帽状物,由帽状物下伸出担子。冬孢子的上细胞和下细胞都可萌发;冬孢子在水中于25℃2h即可萌发,24h后达到萌发高峰,萌发率为12%;温度20-25℃、相对湿度97%以上、pH5-7的条件利于冬孢子萌发,光照对冬孢子萌发没有影响,木糖和乳糖对冬孢子萌发有促进作用;无机氮源营养对冬孢子萌发有抑制作用。肌醇、烟酸、核黄素及三裂叶豚草叶汁对冬孢子萌发有促进作用。     

温度和土壤含水量对青冈栎种子萌发的影响

运用直播法,研究应用人工气候箱控制温度和土壤含水量对野生青冈栎种子萌发和幼苗生长的影响。结果表明:在12h光照条件下,青冈栎种子在变温为10℃/15℃时,萌发率很低,仅为(12±12.29)%;变温为30℃/35℃时,萌发率达最大,为(81±13.7)%。土壤含水量为30%～40%时,萌发率为(79±15.9)%;土壤含水量为90%～100%时,萌发率为(56.67±19.36)%。青冈栎种子萌发呈现出迅速萌发和推迟萌发的特点;温度对青冈栎幼苗的苗高、叶长和叶宽影响显著,对幼苗的地径、叶片数量影响不显著。恒温下,不同梯度土壤含水量处理对幼苗的苗高、地径、叶长、宽影响不显著。     

哈茨木霉的培养及其对烟草疫霉生长的抑制研究

哈茨木霉是一类重要的植病生防因子。哈茨木霉TH-1分别在PDA培养基、麦芽糖培养基、查氏培养基和琼脂培养基上培养均能产孢,其中PDA培养基为最适培养基。PDA培养基上,菌丝生长适宜温度27．5℃～35℃,最适温度32．5℃,产孢最适温度27．5℃。菌丝生长适宜pH值为3～7,产孢适宜pH值为5-9,生长与产孢最适pH值为5。光照对菌丝生长影响不大但明显影响菌株的产孢数量,光照时间越长产孢量越大。对峙培养试验表明TH-1明显抑制疫霉菌的生长速率,其无菌滤液明显抑制烟草疫霉菌游动孢子的萌发,并抑制游动孢子芽管的伸长,TH-1对游动孢子萌发的相对抑制率为12．7％,对芽管生长长度的相对抑制率为63．1％。水解酶平板活性测定显示,TH-1产生β-1,3葡聚糖酶与纤维素酶,从而使烟草疫霉菌细胞壁的消解,产生非挥发性抗生素抑制烟草疫霉菌孢子萌发,但对菌丝生长影响不大。     

芹菜斑枯病菌生物学特性研究

以沈阳地区芹菜斑枯病菌的纯培养菌株为试材,通过对菌丝生长、孢子萌发的营养及环境条件的多因子试验,明确了芹菜斑枯病菌菌丝生长以在CDAMS—VI培养基上最好,其次是CSA、CCSA和PDA,菌丝生长及产孢对碳源、氮源种类有明显的选择性。菌丝生长的最适pH值为4～5,最适温度为21℃,致死温度为39℃（处理40min）,光照明显抑制菌丝生长。病菌分生孢子在水和芹菜汁中不能萌发,在水琼脂上萌发最好;孢子萌发的适宜pH值为4．6～6．6,适温为17—25℃,致死温度为42℃（处理20min）,RH100％最适宜孢子萌发。光照和变温处理可促进分生孢子器的形成,病菌在PDA上从孢子萌发到分生孢子器形成并释放出分生孢子需要16～18d。     

光照与温度对云杉和红桦种子萌发的影响

通过在气候箱内模拟迹地环境条件,探讨了不同温度和光照对亚高山针叶林采伐迹地关键种种子萌发的影响．结果表明,云杉和红桦种子萌发的最适温度均为25℃,发芽率分别为88．8±8．4％和30．8±10．4％,多重比较显示红桦对温度的响应比云杉更敏感．云杉在10℃时能萌发而红桦则几乎不能．红桦种子萌发所需要的最低温度比云杉的高．昼夜温差对两类种子发芽影响明显,20℃／15℃条件下两种种子萌发率最高,温差过大不利于红桦种子萌发．光照强度对种子的发芽率也有明显影响。二者在透光20％时种子发芽率最高,分别为83．2±6．6％和29．2±5．5％,云杉种子萌发对光照的响应比红桦种子更为敏感．采伐迹地强烈的光照是限制亚高山针叶林自然更新的重要因素,迹地温度升高有利于云杉和红桦种子萌发,但剧烈的昼夜温差又在一定程度上抑制了种子萌发。     

乌蕨孢子萌发研究

用随机区组试验和方差分析方法,研究了培养温度、贮藏温度、GA处理和光照强度对乌蕨(Sphe-nomeris chinensis)孢子萌发的影响。与室温(20～25℃)相比,培养温度在28℃时,孢子最大萌发率相近而萌发速率明显较高。贮藏温度(A)极显著(P<0.01)影响孢子萌发率,-20℃贮藏降低萌发率;GA(B)对孢子萌发率无显著影响。光照强度(C)极显著(P<0.01)影响孢子萌发率,充足光照和弱光照无显著差异,黑暗处理降低萌发率。A×B,A×C,B×C及A×B×C交互效应不显著。     

环境因子对努利虫疠霉产孢和孢子萌发的影响

探讨努利虫疠霉Pandoranouryi(Remaudi埁re&Hennebert)H櫣mber在田间蚜虫种群中发生与流行的规律,研究外界环境因子对感菌虫尸产孢和孢子萌发的影响。结果表明,处于水琼脂培养平板上感染努利虫疠霉的桃蚜虫尸在8~25℃的温度范围内均能产生大量的初生分生孢子,在30℃下,仅弹射极少量孢子。8℃下,孢子弹射可以持续120h,当温度高于15℃,大部分的孢子会在48h内完成弹射。相对湿度小于95%,虫尸停止产孢。20℃下,光照条件不会影响虫尸弹射孢子的总量。在8℃和30℃时,24h后处于水琼脂培养平板上的孢子萌发率分别为45.23%和61.74%,显著低于15~25℃温度范围内的孢子萌发率(95%以上)。处于叶片上的真菌孢子,当相对湿度大于74%时出现萌发,但在盖玻片的表面,当湿度低于100%时未发现孢子萌发。     

蝉拟青霉LB菌株的生物学特性

本文研究碳源、氮源、温度、湿度、pH值和光照等对蝉拟青霉LB菌株生长、产孢和孢子萌发的影响.结果表明,适合该菌株菌落生长和产孢的最佳碳源是可溶性淀粉和蔗糖,最佳氮源为蛋白胨;菌丝生长和孢子萌发的最适温度范围是25℃～27℃,产生分生孢子的最适温度是25℃;分生孢子萌发所需湿度范围是RH 90%～100%,当RH低于90%时很难萌发;在pH值4～10的范围内该菌能生长和产孢,菌丝生长最适pH为6,产生分生孢子和孢子萌发最适pH范围为6-7;光照处理对该菌产孢有一定的影响;分生孢子的致死条件为55℃ 10min.生物学特性显示,蝉拟青霉LB菌株是一株对营养要求不高、对环境适应能力较强的昆虫病原真菌.     

Prediction of conidial germination of Penicillium chrysogenum as influenced by temperature, water activity and pH

AIMS: Conidial germination of Penicillium chrysogenum was carried out under operating conditions compatible with a pastries manufacturing process. METHODS AND RESULTS: A range, limited by two experimental values, was defined for each environmental factor tested: temperature (15 or 25 degrees C), water activity (0.75 or 0.85) and pH (3.5 or 5.5). A closed device was made, which maintained an equilibrium between water activity of the culture medium and atmospheric relative humidity during 25 days, to follow spore germination. The combined effects of temperature, water activity and pH on spore germination were studied by applying factorial design methodology. CONCLUSIONS: Higher rates of spore germination were associated with a high level of water activity. The incubation temperature also had a positive effect. A significant positive interaction between water activity and temperature was observed. Under these specific experimental conditions, pH did not have a significant effect on conidial germination. SIGNIFICANCE AND IMPACT OF THE STUDY: A model describing the behaviour of fungal conidia is proposed.     

Nutritional and physiological factors affecting germination of heterothallic Saccharomyces cerevisiae ascospores.

Saccharomyces cerevisiae strain AP-3 was examined with respect to those nutritional requirements and physiological conditions which influence its germination rate. It was found that glucose as a carbon source supported the most rapid rate of germination for this heterothallic strain. In contrast, strain AP-3 spore germination was supported the least by the carbon sources potassium acetate and lactose. Of the nitrogen sources tested in culture medium containing glucose, the complex nitrogen sources peptone and casein hydrolysate appeared to be capable of stimulating germination better than a control culture containing ammonium sulphate. None of the amino acids screened were found to stimulate strain AP-3 germination compared with ammonium sulphate. The optimal culture medium pH for ascospore germination was 4.5 although spore germination could still be initiated by glucose between pH 3.0 and pH 7.5. Germination initiation by glucose was observed over a temperature range from 25 degrees C to 50 degrees C, but the optimal temperature appeared to be 40 degrees C.     

Initiation of Bacillus spore germination by hydrostatic pressure: effect of temperature.

Suspensions of Bacillus cereus T, B. subtilis, and B. pumilus spores in water or potassium phosphate buffer were germinated by hydrostatic pressures of between 325 and 975 atm. Kinetics of germination at temperatures within the range of 25 to 44 degrees C were determined, and thermodynamic parameters were calculated. The optimum temperature for germination was dependent on pressure, species, suspending medium, and storage time after heat activation. Germination rates increased significantly with small increments of pressure, as indicated by high negative deltaV values of -230 +/- 5 cm3/mol for buffered B. subtilis (500 to 700 atm) and B. pumilus (500 atm) spores and -254 +/- 18 cm3/mol for aqueous B. subtilis (400 to 550 atm) spores at 40 degrees C and -612 +/- 41 cm3/mol for B. cereus (500 to 700 atm) spores at 25 degrees C. The ranges of thermodynamic constants calculated at 40 degrees C for buffered B. pumilus and B. subtilis spores at 500 and 600 atm and for aqueous B. subtilis spores at 500 atm were: Ea = 181,000 to 267,000 J/mol; deltaH = 178,000 to 264,000 J/mol; deltaG = 94,000 to 98,300 J/mol; deltaS = 264 to 544 J/mol per degree K. These values are consistent with the concept that the transformation of a dormant to a germinating spore induced by hydrostatic pressure involves either hydration or a reduction in the visocosity of the spore core and a conformational change of an enzyme.     

The effect of temperature and pH on ethanol production by free and immobilized cells of Kluyveromyces marxianus grown on Jerusalem artichoke extract

The effect of temperature and pH on the kinetics of ethanol production by free and calcium alginate immobilized cells of Kluyveromyces marxianus grown on Jerusalem artichoke extract was investigated. With the free cells, the ethanol and biomass yields were relatively constant over the temperature range 25-35 degrees C, but dropped sharply beyond 35 degrees C. Other kinetic parameters, specific growth rate, specific ethanol production rate, and specific total sugar uptake rate were maximum at 35 degrees C. However, with the immobilized cells, ethanol yield remained almost constant in the temperature range 25-45 degrees C, and the specific ethanol production rate and specific total sugar uptake rate attained their maximum values at 40 degrees C. For the pH range between 3 and 7, the free-cell optimum for growth and product formation was found to be ca. pH 5. At this pH, the specific growth rate was 0.35 h(-1) and specific ethanol production rate was 2.83 g/g/h. At values higher or lower than pH 5, a sharp decrease in specific ethanol production rate as well as specific growth rate was observed. In comparison, the immobilized cells showed a broad optimum pH profile. The best ethanol production rates were observed between pH 4 and 6.     

FACTORS AFFECTING GERMINATION IN GREENHOUSE-PRODUCED SEEDS OF OXALIS CORNICULATA,A PERENNIAL WEED

A study was conducted to investigate the physiological responses of greenhouse-produced Oxalis corniculata seeds to light, temperature, moist heat treatment, aging, and season of production. Fresh seeds exhibited over 90% germination and required low levels of light (5 μmol m^-2 s^-1, 400–700 nm) to germinate. Seeds germinated over a broad, yet seasonally-dependent range of incubation temperatures. Seeds produced in winter had the narrowest temperature range of germination (15 to 25 C) and the lowest germination percent (44% at 2 wk) at optimum temperature (17 C); seeds produced in summer had the widest temperature range of germination (10 to 30 C) and the highest germination percent (93% at 2 wk) at optimum temperature (17 C). Incubation at non-optimum temperatures between 5 and 40 C suppressed or slowed the rate of germination until seeds were placed at optimum temperature, where full germination subsequently occurred. Moist heat treatment at temperatures over 40 C resulted in varying degrees of inhibition of subsequent germination. When seeds were stored dry in laboratory conditions, three of four seed lots examined retained over 80% germination capacity until ca. 8 months; 50% capacity remained after ca. 15 months. These results indicate that the seasonal temperature and daylength effects on maternal plants in the greenhouse environment are major determinants of seed germination characteristics of O. corniculata.     

Water vapor, aqueous ethyl alcohol, and heat activation of Bacillus megaterium spore germination

Dormant spores of Bacillus megaterium were activated for germination on glucose by heating them in aqueous suspension (but not if heated dry), by treating them with aqueous ethyl alcohol at 30 C, or by exposing them to water vapor at room temperature. The degree of water vapor activation depended upon the relative humidity, the time, and the temperature of exposure. Activation increased the extent and rate of glucose-induced germination and decreased the average microlag. Extended water vapor treatment also activated spores for germination induced by KI and by l-alanine. Spores activated by any of the three treatments were deactivated by treatment at 66 C, either for 18 hr in 100% ethyl alcohol or for 40 hr over P(2)O(5). Deactivated spores were reactivated by heat, by 5 m ethyl alcohol, or by water vapor. It is postulated that heating and ethyl alcohol may change the structure of liquid water, so that it is more like water vapor and can more readily penetrate to and hydrate a critical (enzymatic?) spore site, leading to activation.     

Thermal analysis of the spores of Bacillus cereus with special reference to heat activation.

The heat activation of bacterial spores was studied by means of differential thermal analysis in the temperature range 30-110 degrees C using the spores of Bacillus cereus. The thermogram showed three endothermic peaks at 56, 95, and 103 degrees C with one exothermic peak at 105 degrees C during the heating process. The spore coat separated from the native spores also showed a peak at 56 degrees C on its heating thermogram. The peak at 56 degrees C was reversible for both native spores and the spore coat. It was suggested that this peak at 56 degrees C might be related to the heat-activation process that takes place in the spore-coat region. It seems that the peak is due to the denaturation or the structural change of the spore-coat protein that might facilitate either the permeation of germination stimulators or the release of some germination inhibitor into or out of the spores.     

Effects of temperature,pH and water potential on growth of four fungi with disease biocontrol potential

Effects of temperature, pH and water potential on blomass production or hyphal extension of Gliocladium virens (G20) and three Trichoderma isolates were determined in vitro. Optimum blomass production occurred between 20 and 30°C and at pH ranges between 4.6 and 6.8. Two isolates of T. viride grew at 5°C and G. virens grew at 35°C but no isolates grew at 40°C. Hyphal extension rates and conidial germination of all fungi declined with decreasing water potential over the range -0.7 to -14.0 MPa. In general, growth rates for each isolate were lower on potato/dextrose agar with water potential adjusted with polyethylene glycol than when adjusted with NaCl or glycerol. No mycelial growth or spore germination occurred on agar at-14.0 MPa.The authors are with the Microbiology and Crop Protection Department, Horticulture Research International, Littlehampton, West Sussex BN17 6LP, UK. J.M. Whipps is the corresponding author     

Effects of temperature on the spores of thermophilic actinomycetes

The effects of temperature on the germination properties of spores of thermophilic actinomycetes were examined. Temperatures above and below the growth temperature of 55° C were found to produce marked changes in the germination properties of spores. High temperatures caused reductions in the germinative activities of spores. However, heated spore populations regained original germinative activities after maintaining them for suitable periods of time at 25°C. Recovery from the effects of heat on spore germination was also observed at 4°C, but at a much slower rate compared with 25°C. Spores of two strains of thermophilic actinomycetes, grown and prepared at 55°C, failed to germinate. Storage of dormant (nonactivated) spore populations at different temperatures demonstrated a low temperature requirement for the activation of these spores; while little or no activation occurred at 55°C, rapid activation took place at 25°C. Heating the spores at 80°C for 30 min slightly delayed the activation (rates) of spores at 25°C. The requirement of low temperature for spore activation was strain dependent and was influenced by the composition of the germination medium.