桢楠种子萌发过程中内源激素对温度变化的响应

【目的】研究低温(4℃)保存和自然保存两种处理后,桢楠种子在恒温(25℃)和变温(15℃/25℃)条件的萌发过程中,种子内源激素含量及其动态变化,以及内源激素与种子萌发率的关系,为阐明桢楠种子的萌发机制提供理论基础,也为其繁育与开发应用提供参考依据。【方法】采用酶联免疫吸附测定法对桢楠种子的内源激素含量及动态变化进行测定。【结果】1)自然保存的种子在恒温(25℃)条件下发芽率不足30%,最高为27.3%,在变温(15℃/25℃)条件下的发芽率不足40%,最高为37.0%,而经过低温(4℃)处理的种子在变温(15℃/25℃)条件下的发芽率最高可达66.0%;2)经过低温(4℃)处理后的种子在变温(15℃/25℃)条件下的内源激素含量GA3为417.17 ng·g-1,IAA为211.67 ng·g-1,ZR为47.69 ng·g-1,均高于恒温(25℃)下的GA3、IAA、ZR含量,GA3和ZR含量呈现出先上升后下降趋势,ABA和IAA含量则表现为先下降后上升趋势;3)在变温(15℃/25℃)条件下内源激素GA3/ABA、ZR/ABA、(GA3+IAA+ZR)/ABA比值均比恒温(25℃)条件下高;4)在恒温(25℃)条件和变温(15℃/25℃)条件下的种子发芽率与GA3/ABA、IAA/ABA、ZR/ABA及(GA3+IAA+ZR)/ABA的比值均呈显著或极显著正相关。【结论】低温(4℃)可以解除桢楠种子的休眠,显著提高种子的发芽率,在变温(15℃/25℃)条件能够打破种子内源激素间的平衡,增加促进种子萌发的内源激素含量,降低抑制种子萌发的内源激素含量,进而提高种子的发芽率。     

光皮树花芽分化与内源激素含量的关系

以4年生光皮树嫁接苗为材料,在研究花芽分化过程中解剖学特征的基础上,测定同品系、同龄的光皮树叶内生长素(IAA)、赤霉素(GA3)、玉米核苷素(ZR)、脱落酸(ABA)等4种内源激素含量的动态变化,研究其成花过程中叶片内源激素含量的变化与成花的关系。结果表明:光皮树花芽分化过程可划分为5个时期:花芽未分化期、花序分化期、花萼分化期、花瓣分化期和雌、雄蕊分化期,其中花序分化期还可分为分化前期和分化后期;在花芽分化阶段,IAA、GA3含量保持稳定的相对较低水平,ABA含量高且变化幅度较大,ZR含量相对较低,但随着花的形成含量逐渐升高;高水平的ABA/IAA有利于花芽的形态分化,低水平的ZR/GA3有利于花芽孕育。4种内源激素含量的动态变化均影响光皮树的成花过程。     

Correlation between endogenous hormones contents and flower bud differentiation of Comus wilsoniana

以4年生光皮树嫁接苗为材料,在研究花芽分化过程中解剖学特征的基础上,测定同品系、同龄的光皮树叶内生长素(IAA)、赤霉素(GA3)、玉米核苷素(ZR)、脱落酸(ABA)等4种内源激素含量的动态变化,研究其成花过程中叶片内源激素含量的变化与成花的关系.结果表明:光皮树花芽分化过程可划分为5个时期:花芽未分化期、花序分化期、花萼分化期、花瓣分化期和雌、雄蕊分化期,其中花序分化期还可分为分化前期和分化后期;在花芽分化阶段,IAA、GA3含量保持稳定的相对较低水平,ABA含量高且变化幅度较大,ZR含量相对较低,但随着花的形成含量逐渐升高;高水平的ABA/IAA有利于花芽的形态分化,低水平的ZR/GA3有利于花芽孕育.4种内源激素含量的动态变化均影响光皮树的成花过程.     

生长调节剂对南方红豆杉大孢子叶球和内源激素的影响

【目的】研究不同生长调节剂对南方红豆杉叶片内源激素含量的动态变化和开花特性的影响,为优化栽培方式、提高种子产量提供参考依据。【方法】以13年生南方红豆杉雌株为研究材料,连续3次叶面喷施不同种类和质量浓度的生长调节剂,通过测定叶片内源激素的动态变化和统计标准枝上生殖枝比例和大孢子叶球数量,分析不同生长调节剂对南方红豆杉的影响规律。【结果】叶面喷施1 500 mg·L~(-1)多效唑、450 mg·L~(-1)矮壮素和2 000 mg·L~(-1)复硝酚钠均能有效促进南方红豆杉的大孢子叶球数量(P 0.05)。三者降低了叶片中GA3含量(除9月上旬的450 mg·L~(-1)矮壮素处理外),提升了9月上旬ZR含量,同时降低了IAA含量,且均达显著水平。另外,1 500 mg·L~(-1)多效唑升高了8月上下旬、9月上旬叶片中ABA/IAA、ABA/GA3、ZR/IAA、ZR/GA3比值;450 mg·L~(-1)矮壮素则增加了9月上下旬ABA/IAA、ZR/IAA和ZR/GA3以及8月、9月的ABA/GA3比值;2 000 mg·L~(-1)复硝酚钠提升了8月下旬、9月上旬的ABA/IAA、ZR/GA3,9月上旬的ZR/IAA和9月下旬的ABA/GA3比值,且均达显著水平。【结论】叶面喷施1 500 mg·L~(-1)多效唑、450 mg·L~(-1)矮壮素和2 000 mg·L~(-1)复硝酚钠均能显著增加南方红豆杉的大孢子叶球数量,这可能是由于处理改变了内源激素的含量和比值,特别是增加了ZR含量和ABA/IAA、ABA/GA3、ZR/IAA、ZR/GA3比值,降低了IAA和GA3含量。在生产中,可以据此结论进行适当的栽培管理。     

双季板栗休眠期至花期芽体或花序内源激素的变化

【目的】研究双季板栗休眠至花期(雌花序出现)结果母枝混合芽和结果枝基部叶芽、纯雄花序、混合花序内源激素含量及其比值,为板栗花芽分化调控提供理论参考。【方法】在双季板栗休眠期前期每隔30 d、休眠末期至芽体萌动每隔15 d采集结果母枝混合花芽,在萌动至花期每隔3～5 d采集结果枝基部叶芽、混合花序和纯雄花序,测定ZR、IAA、GA_3和ABA含量,分别以C(ZR)、C(IAA)、C(GA_3)和C(ABA)表示。【结果】各时期IAA和ABA含量均高于ZR和GA_3含量,C(GA_3)/C(ZR)和C(IAA)/C(ABA)值均显著高于C(GA_3)/C(IAA)、C(GA_3)/C(ABA)、C(ZR)/C(ABA)和C(ZR)/C(IAA)值。在休眠至萌动期,混合花芽IAA含量从11.810 ng/g上升至36.770 ng/g,ABA含量从148.312 ng/g下降至64.938 ng/g,IAA含量在萌动前极显著升高,ABA含量极显著下降;C(IAA)/C(ABA)值从0.072显著上升为0.566,C(ZR)/C(IAA)和C(GA_3)/C(IAA)值下降最显著,分别从0.721和0.445下降至0.263和0.158。在萌动至花期,混合花序和结果枝基部叶芽IAA含量呈抛物线变化,纯雄花序呈不规则抛物线变化,均于3月30日达到峰值,分别为102.801、89.466、112.850 ng/g;各部位ABA含量呈波浪形变化,GA_3与ZR含量呈无明显规律的波动变化;混合花序和纯雄花序C(GA_3)/C(ZR)和C(GA_3)/C(IAA)值整体呈上升趋势,在现雄期至现雌期大幅上升并表现为混合花序C(GA_3)/C(ZR)和C(GA_3)/C(IAA)值高于纯雄花序;结果枝基部叶芽、纯雄花序和混合花序C(GA_3)/C(ABA)、C(IAA)/C(ABA)和C(ZR)/C(ABA)值的变化规律相似,在开始出现纯雄花序后,纯雄花序C(GA_3)/C(ABA)、C(ZR)/C(ABA)和C(IAA)/C(ABA)值均高于混合花序;C(ZR)/C(IAA)值与其他指标值的变化规律不同。【结论】高C(IAA)/C(ABA)值、低C(ZR)/C(IAA)和C(GA_3)/C(IAA)值共同作用,在促进芽萌动方面可能起重要作用。C(GA_3)/C(ZR)、C(GA_3)/C(ABA)、C(ZR)/C(ABA)和C(IAA)/C(ABA)值可能影响板栗的花性,高C(GA_3)/C(ZR)值、低C(GA_3)/C(ABA)值、低C(ZR)/C(ABA)值和低C(IAA)/C(ABA)值有利于雌花形成。     

扇脉杓兰种子发育过程中的生理生化变化

为了解扇脉杓兰种子发育过程中的生理特性和变化规律,以浙江省天目山国家级自然保护区内的2个野生扇脉杓兰居群为材料,对其种子发育过程中的营养物质、内源激素含量和酶活性进行测定。结果表明:(1)可溶性蛋白质含量在扇脉杓兰授粉后20 d和85 d分别达到最高值774.03μg·g^-1和最低值373μg·g^-1。淀粉含量从最初的2.65%急速增加到21.82%,授粉后60 d升至峰值,此后保持在20%左右。可溶性糖含量为1.72% 3.09%。淀粉和可溶性糖之间呈极显著正相关(P<0.01),二者与可溶性蛋白质之间呈极显著负相关(P<0.01)。(2)GA₃、ZR、IAA峰值发生具有时间顺序性,扇脉杓兰授粉后20、30、40 d依次出现。3种激素极显著正相关(P<0.01)。ABA含量在授粉60 d后逐渐上升,授粉115 d时达到峰值,其含量与3种促进激素呈显著负相关(P<0.05)。(IAA+GA₃+ZR)∕ABA比值在授粉后20 d达到峰值,此后逐渐下降。(3)SOD活性在扇脉杓兰授粉后20 d迅速上升至峰值451.18 U·g^-1·min^-1,授粉后85 d降至最低,其变化趋势与可溶性蛋白质变化保持一致。POD活性和CAT活性呈单峰曲线变化。SOD、POD和CAT活性之间相关不显著(P>0.05),但是三者与可溶性蛋白质之间呈显著正相关(P<0.05)。     

油桐花芽分化期内源激素含量的变化

为给油桐花芽分化及花期调控的研究提供理论依据.在观察油桐花芽形态分化的显微结构的基础上,测定并分析了该时期油桐叶片中内源激素ZR(玉米索核苷)、IAA(生长素)、GA(赤霉素)、ABA(脱落酸)含量的变化情况.结果表明:当花芽生理分化期,ZR(玉米素核苷)、IAA(生长素)、GA(赤霉素)、ABA(脱落酸)的含量迅速下降,到花芽形态分化开始前降到较低水平;花芽形态分化开始后,ZR(玉米素核苷)、IAA(生长素),GA(赤霉素),ABA(脱落酸)的含量呈现出前期上升、中期波动、末期上升的变化规律;花芽生理分化期,ZR/GA、ZR/IAA、ABA/GA和ABA/IAA之值迅速上升,而当花芽形态分化期,各比值在较高水平上的波动大.后期下降.因此,内源激素间的平衡与综合作用促进了花芽的分化.     

休眠解除后山桐子种子萌发过程中内源激素的动态变化

【目的】探讨低温解除休眠处理后,山桐子种子在萌发过程中内源激素的动态变化及与种子萌发的关系,为明确山桐子种子萌发机制提供依据,也为其繁育与开发应用提供理论基础及技术支撑。【方法】采用酶联免疫法对济源种源山桐子种子进行内源激素含量动态变化的测定。【结果】1)25℃恒温条件下,济源山桐子种子萌发率均低于10%;15℃/25℃变温条件下,没有经历低温处理的山桐子种子发芽率仅为33%~37%,随着5℃低温处理时间的延长,发芽率逐渐升高,60天低温处理的济源山桐子种子发芽率可达98.0%。2)15℃/25℃变温条件下,济源山桐子种子内源激素IAA、GA_3、ZR含量均明显高于25℃恒温,而ABA含量正好相反,(IAA+GA_3+ZR)/ABA或GA_3/ABA比值变大。3)在变温条件下,没有低温处理的山桐子萌发过程中IAA与ABA含量均呈下降趋势,而GA_3与ZR含量均呈先升高再降低的趋势,但经过5℃低温处理的山桐子种子只有ABA含量呈下降趋势,而IAA、GA_3、ZR含量均呈先升高再降低的趋势,差别是峰值出现时间不同。4)不同低温处理时间,(IAA+GA_3+ZR)/ABA与GA_3/ABA的比值在种子萌发过程中均呈先升高再降低的趋势,峰值分别达到3.8±0.2,2.0±0.1,但达到峰值的时间不同,0、20、40和60天的比值达到峰值的时间分别为20、12、12天或8天、8天。5)不同低温处理时间山桐子种子发芽率虽与单一内源激素没有相关性,但与(IAA+GA_3+ZR)/ABA与GA_3/ABA比值均达到显著或极显著相关。【结论】济源山桐子种子具有明显的冬休眠特征,在变温条件下经历不同时间5℃低温解除休眠后的济源山桐子在萌发过程中(IAA+GA_3+ZR)/ABA以及GA_3/ABA比值升高达到峰值的时间越早发芽率越高,当比值达到峰值的时间缩短到8天时,发芽率最大。低温解除休眠的作用是使山桐子种子在萌发过程中及早达到内源激素的平衡态。     

~(60)Co-γ对海州常山扦插过程内源激素含量的变化影响

以海州常山(Clerodendrum trichotomum Thumb)1年生休眠枝条为材料,采用60Co-γ射线(剂量15Gy)处理扦插插穗,未经辐射处理为对照。于扦插后40d、47d、54d、64d、74d、84d和104d从辐射与对照处理插穗基部皮部取样,测定生根过程中内源激素生长素(IAA)、赤霉素(GA3)、脱落酸(ABA)和玉米素(ZR)含量的动态变化。结果显示:60Co-γ射线抑制海州常山扦插生根。与对照相比,15Gy的60Co-γ射线辐射处理组的内源IAA含量、ABA含量和ZR含量均在不定根诱导和形成期间多上升,GA3含量、IAA/ABA,GA3/ABA,ZR/ABA比值含量降低,IAA和ZR含量谷值推后到来。60Co-γ辐射处理提高不定根形成期内源ABA含量,从而IAA/ABA,GA3/ABA,ZR/ABA比值降低,这是插穗生根推迟的主要原因。     

光皮树花中内源激素和碳水化合物含量的变化

以4年生光皮树嫁接苗为材料,采用酶联免疫吸附法(ELISA)测定同品系同龄的光皮树叶内4种内源激素生长素(IAA)、赤霉素(GA3),玉米核苷素(ZR)、脱落酸(ABA)含量的动态变化.研究成花过程中叶片内源激素含量的变化与成花的关系.研究结果表明:在花芽分化时期,IAA、GA3含景保持相对较低和稳定的水平,ABA含量高且变化幅度较大,ZR含量相对较低,但随着花的形成含量逐渐升高;因此,4种内源激素含量的动态变化影响光皮树的成花过程.碳水化合物含量的变化随着花芽分化而不断升高,并且高于花芽分化前期的水平,说明一定量碳水化合物的积累有利于花芽分化.     

Antibacterial activity of plant extracts from Brazilian southeast region

A screening was conducted with 26 plants collected in the Brazilian southeast region, to identify plant extracts with antibacterial properties against Aeromonas hydrophila, Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus. Initially, the agar diffusion method was employed. Then, those extracts presenting activity were submitted to a broth microdilution assay to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). It was observed that 13 of the tested extracts showed antibacterial activity. The best results were obtained with those from Lantana lilacina and Phyllanthus tenellus.     

Antimicrobial activity of some endemic plants growing in the Eastern Black Sea Region, Turkey

The Eastern Black Sea Region has an extensive flora because of ample rainfall lasting all year. In this study, antimicrobial effects of 74 crude extracts of 22 endemic plants were investigated. Among the 30 active crude extracts, water-insoluble crude extracts from Betula medwediewii, Heracleum platytaenium, Primula longipes, Anthemis cretica ssp. argaea and Centaurea helenioides were the prominent ones with their MIC values.     

Anti-HBV activities of Streblus asper and constituents of its roots

The extracts from leaves, heartwood, barks and roots of the Streblus asper were investigated for anti-HBV activities, separately. The results suggested that the MeOH extracts of the heartwood, barks, and roots exhibited good anti-HBV activities. Further investigations displayed that ethyl acetate and n-butanol soluble parts of their MeOH extracts showed more significant anti-HBV activities. Moreover, a new lignan, together with 11 known compounds, was isolated from n-butanol-soluble part of MeOH extract of the roots of S. asper. The structures were elucidated by spectroscopic methods, including 1D NMR ((1)H NMR, (13)C NMR), 2D NMR (HMQC, HMBC) and HR-EI-MS experiments. Compounds 1-3 were evaluated for their anti-HBV activities. Honokiol showed significant anti-HBV activity with IC(50) values of 3.14μM and 4.74μM for HBsAg and HBeAg with no cytotoxicity respectively, while lamivudine (3TC, positive control) exhibited weak anti-HBV activity with IC(50) values of 11.81μM and 25.80μM for HBsAg and HBeAg respectively.     

Growth and physiological response of six Australian rainforest tree species to a light gradient

An understanding of growth and photosynthetic potential of subtropical rainforest species to variations in light environment can be useful for determining the sequence of species introductions in rainforest restoration projects and mixed species plantations. We examined the growth and physiology of six Australian subtropical rainforest tree species in a greenhouse consisting of three artificial light environments (10%, 30%, and 60% full sunlight). Morphological responses followed the typical sun-shade dichotomy, with early and late secondary species (Elaeocarpus grandis, Flindersia brayleyana, Flindersia schottiana, and Gmelina leichhardtii) displaying higher relative growth rate (RGR) compared to mature stage species (Cryptocarya erythroxylon and Heritiera trifoliolatum). Growth and photosynthetic performance of most species reached a maximum in 30–60% full sunlight. Physiological responses provided limited evidence of a distinct dichotomy between early and late successional species. E. grandis and F. brayleyana, provided a clear representation of early successional species, with marked increase in A_max in high light and an ability to down regulate photosynthetic machinery in low light conditions. The remaining species (F. schottiana, G. leichhardtii, and H. trifoliolatum) were better represented as falling along a shade-tolerant continuum, with limited ability to adjust physiologically to an increase or decrease in light, maintaining similar A_max across all light environments. Results show that most species belong to a shade-tolerant constituency, with an ability to grow and persist across a wide range of light environments. The species offer a wide range of potential planting scenarios and silvicultural options, with ample potential to achieve rapid canopy closure and rainforest restoration goals.     

Photosynthetic characteristics of Fagus sylvatica and Quercus robur established for stand conversion from Picea abies

Efforts in Europe to convert Norway spruce (Picea abies) plantations to broadleaf or mixed broadleaf-conifer forests could be bolstered by an increased understanding of how artificial regeneration acclimates and functions under a range of Norway spruce stand conditions. We studied foliage characteristics and leaf-level photosynthesis on 7-year-old European beech (Fagus sylvatica) and pedunculate oak (Quercus robur) regeneration established in open patches and shelterwoods of a partially harvested Norway spruce plantation in southwestern Sweden. Both species exhibited morphological plasticity at the leaf level by developing leaf blades in patches with an average mass per unit area (LMA) 54% greater than of those in shelterwoods, and at the plant level by maintaining a leaf area ratio (LAR) in shelterwoods that was 78% greater than in patches. However, we observed interspecific differences in photosynthetic capacity relative to spruce canopy openness. Photosynthetic capacity (A₁₆₀₀, net photosynthesis at a photosynthetic photon flux density of 1600 μmol photons m⁻² s⁻¹) of beech in respect to the canopy gradient was best related to leaf mass, and declined substantially with increasing canopy openness primarily because leaf nitrogen (N) in this species decreased about 0.9 mg g⁻¹ with each 10% rise in canopy openness. In contrast, A₁₆₀₀ of oak showed a weak response to mass-based N, and furthermore the percentage of N remained constant in oak leaf tissues across the canopy gradient. Therefore, oak photosynthetic capacity along the canopy gradient was best related to leaf area, and increased as the spruce canopy thinned primarily because LMA rose 8.6 g m⁻² for each 10% increase in canopy openness. These findings support the premise that spruce stand structure regulates photosynthetic capacity of beech through processes that determine N status of this species; leaf N (mass basis) was greatest under relatively closed spruce canopies where leaves apparently acclimate by enhancing light harvesting mechanisms. Spruce stand structure regulates photosynthetic capacity of oak through processes that control LMA; LMA was greatest under open spruce canopies of high light availability where leaves apparently acclimate by enhancing CO₂ fixation mechanisms.     

利用三种梢栖真菌生物防治落叶松枯梢病的研究

从落叶松梢栖真菌筛选出对落叶松枯梢病病原菌有抑制作用的菌株,对落叶松枯梢病进行生物防治。将自落叶松梢部分离到的11种梢栖真菌与落叶松枯梢病病原菌进行对峙培养,根据被覆盖程度、抑菌率、拮抗系数和防治预试验的结果,综合评价后发现:粪生粪壳、深绿木霉和球毛壳3种梢栖真菌对落叶松枯梢病有良好的拮抗作用。利用这3个菌株在黑龙江省勃利县通天一林场国富沟进行林间防治试验,结果表明:防治效果为粪生粪壳>代森锰锌400倍液>深绿木霉>球毛壳;深绿木霉和粪生粪壳喷洒浓度50%和球毛壳喷洒浓度75%时,真菌多样性最多,梢栖真菌系统较其他浓度更为稳定,与化学防治相比,既达到了防治目的又具有不污染环境的优势。     

Ungulate herbivory of regenerating conifers in relation to foliar nutrition and terpenoid production

Ungulate browsing greatly influences regeneration dynamics of some forest ecosystems, yet the relationship between browse susceptibility and foliar chemistry of forest tree seedlings is not well understood. We applied field fertilization (15N-9P-10K controlled-release fertilizer at 0, 20, 40, and 60 g per seedling) and investigated how subsequent changes in terpenoid production and foliar nutrition influence ungulate browse preference for Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western hemlock (Tsuga heterophylla Raf. Sarg.), and western redcedar (Thujaplicata Donn ex D. Don) seedlings across four sites in northwestern Oregon, USA. Fertilization increased foliar N concentration of all three species, but above-ground growth of only Douglas-fir and western hemlock. Foliar monoterpene concentrations for western hemlock and western redcedar also increased at higher fertilization rates, while Douglas-fir monoterpene production was not affected by fertilization. Regardless of monoterpene levels, ungulate browse preference was greater for fertilized western hemlock seedlings. The opposite response, however, was observed for western redcedar at two of the four study sites where the likelihood of browse was greater for non-fertilized than fertilized seedlings. Differences in browse preference among species may depend on the type and amount of individual monoterpenes manufactured in response to fertilization. Western redcedar produce α- and β-thujone, oxygenated monoterpenes known to promote gastroenteritis and possibly inhibit microbial rumen activity, which were absent from Douglas-fir or western hemlock. Higher concentrations of α- and β-thujone associated with increasing fertilizer rate provide a plausible explanation as to why ungulates preferred non-fertilized western redcedar. Our results illustrate species-specific adaptation in browse avoidance and selective ungulate browsing behavior of individual trees as linked to foliar chemistry.     

Effects of prescribed fire and season of burn on direct and indirect levels of tree mortality in Ponderosa and Jeffrey Pine Forests in California,USA

Many forests that historically experienced frequent low-intensity wildfires have undergone extensive alterations during the past century. Prescribed fire is now commonly used to restore these fire-adapted forest ecosystems. In this study, we examined the influence of prescribed burn season on levels of tree mortality attributed to prescribed fire effects (direct mortality) and bark beetles (Coleoptera: Curculionidae, Scolytinae) (indirect mortality) in ponderosa pine, Pinusponderosa Dougl. ex Laws., and Jeffrey pine, Pinusjeffreyi Grev. and Balf., forests in California, USA. A total of 816 trees (9.9% of all trees) died during this 3-yr study. Significantly higher levels of tree mortality (all sources) occurred following early and late season burns compared to the untreated control, but no significant difference was observed between burn treatments. The majority (461 trees) of tree deaths were attributed to direct mortality from prescribed burns and was strongly concentrated (391 trees) in the smallest diameter class (<20.2 cm diameter at breast height, dbh). For the largest trees (>50.7 cm dbh), significantly higher levels of tree mortality occurred on early season burns than the untreated control, most of which resulted from indirect mortality attributed to bark beetle attacks, specifically western pine beetle, Dendroctonus brevicomis LeConte, and mountain pine beetle, D. ponderosae Hopkins. Red turpentine beetle, D. valens LeConte, was the most common bark beetle species found colonizing trees, but tree mortality was not attributed to this species. A total of 355 trees (4.3% of all trees) were killed by bark beetles. Dendroctonus brevicomis (67 trees, 18.9%) and D. ponderosae (56 trees, 15.8%), were found colonizing P. ponderosa; and Jeffrey pine beetle, D. jeffreyi Hopkins, was found colonizing P. jeffreyi (seven trees, 2.0%). We also found pine engraver, Ips pini (Say) (137 trees, 38.6%), and, to a much lesser extent, Orthotomicus (=Ips) latidens (LeConte) (85 trees, 23.9%) and emarginate ips, I. emarginatus (LeConte) (3 trees, 0.8%) colonizing P. ponderosa and P. jeffreyi. Few meaningful differences in levels of indirect tree mortality attributed to bark beetle attack were observed between early and late season burns. The incidence of root and root collar pathogens (Leptographium and Sporothrix spp.), including species known to be vectored by bark beetles, was low (18% of trees sampled). The implications of these and other results to management of P. ponderosa and P. jeffreyi forests are discussed in detail.     

Screening of antioxidant activity of three Euphorbia species from Turkey

Euphorbia acanthothamnos, E. macroclada and E. rigida were investigated for their antioxidant activity. The antioxidant potential of extracts of E. acanthothamnos, E. macroclada and E. rigida was evaluated using different complementary antioxidant tests.