滇西南巨尾桉人工林木根径、胸径与树高模型研究

为研究巨尾桉人工林林木根径、胸径与树高数学模型,在滇西南的双江县选取138株（其中建模样本103株,检验样本35株）树干健全、通直圆满、无分杈的巨尾桉人工林样木,采集其根径与树高、胸径与树高成对数据。利用SPSS 21.0回归分析,分别建立线性方程、对数曲线、指数曲线和Logistic曲线等11个数学模型,以决定系数（R²）、估计值的标准误（SEE）、均方差（RMSE）、平均绝对偏差(MAD)、相对误差（RS）、模型预估精度（P）、显著性(Sig)P值作为模型评价指标,对比11个模型的拟合效果。结果表明,11个根径—树高模型显著性（Sig）P<0.001,其中有9个模型的预估精度大于97%,回归方程达到极显著水平,拟合效果较好;11个胸径—树高模型显著性（Sig）P<0.001,其中9个模型的预估精度大于97%,回归方程达到极显著水平,拟合效果也较好。通过对各项评价指标进行比较分析,确定三次项曲线H=a₀+a₁DR+a₂DR²+a₃DR³是拟合效果最好的根径—树高数学模型,代入拟合参数后的根径—树高数学模型表达式为H=11.069901-0.729389DR+0.096782DR²-0.001984DR³;线性方程H=a₀+a₁D是拟合效果最好的胸径—树高数学模型,代入拟合参数的胸径—树高数学模型表达式为H=4.818702+0.891217D。     

BCI 50 hm2森林大样地2010年活立木空间结构分析

[目的]以BCI 50 hm²大样地为研究对象,利用空间结构参数一元分布和二元分布,量化评价BCI 50 hm²大样地活立木整体、冠层和下层的空间结构特征。[方法]以巴拿马BCI 50 hm²森林大样地（2010年第7次调查）中所有胸径（DBH）≥ 1 cm的活立木数据为材料,采用基于相邻木关系的空间结构参数方法对其整体、冠层和下层活立木的空间结构进行分析。[结果]表明：BCI大样地第7次调查整体活立木的平均角尺度（W）为0.504,样地大部分林木处于极强度混交状态（M_i=1）,比例为74.7%。样地的冠层和下层的状态与整体林分的状态相同,均处于随机分布、强度混交和中庸偏劣势的状态。冠层中几乎没有林木个体处于零度混交（M_i=0）状态。下层的大部分林木处于中高度大小比数和中高度混交度等级的组合上。样地中大部分活立木为小径级个体（1 cm ≤ DBH < 20 cm）,使得样地中大部分林木处于劣势状态。无论在整体、冠层和下层,活立木的混交度（M_i）都处于极高水平,在参照树周围的最近4株相邻木中同种个体的比例（M_i=0.00,M_i=0.25）极低。[结论] BCI大样地整体、冠层和下层活立木空间结构呈随机分布,林木的混交度极高,样地中同种个体在最近4株邻体这样的小尺度上呈现聚集分布的情况几乎不存在。     

宁夏六盘山香水河小流域华北落叶松人工林乔木层生物量的坡面变化和尺度效应

生物量受坡面环境条件变化影响而有坡面变化与尺度效应。本文在六盘山半湿润区的香水河小流域选择了33 a生华北落叶松人工林的一个斜坡长480 m,水平长398 m的典型坡面,在整个坡面上建立了宽30 m的调查样带,均匀分为空间连续的16个样地,在2014年生长季中期调查不同坡位的样地生物量,分析其坡面变化规律。结果表明:生物量存在明显的坡位差异。坡面生物量t·hm^-2平均值为118.59,其变化范围为96.19 139.18,变幅为42.99,变异系数为0.12;随着离坡顶距离的增加,生物量总体上呈现先升高后降低的变化趋势,在坡面的中上部(水平坡长为87.71 m)达到最大。生物量存在坡面空间尺度效应,即随着相对坡长(X₁)的增加,生物量的顺坡滑动平均值(Y₁)先增大后减小,其回归关系式为:Y₁=23.004X₁³-60.834X₁²+31.786X₁+123.43(R²=0.84),坡面尺度效应表现为每100 m水平坡长生物量变化的数值为6.12 t·hm^-2;各样地生物量与整个坡面平均值的比值(Y₂,小数)随相对坡长有很好的非线性关系,基本上呈先增加后下降、后趋于稳定的变化趋势,其关系式为Y₂=1.722 6X₁³-2.844 5X₁²+1.033 8X₁+1.000 1(R²=0.57),可基于此将特定坡位样地的生物量换算成整个坡面的估算值。造成生物量坡面变化的主要原因是太阳辐射和光照时间随海拔的变化等多种因素造成的。     

Photosynthetic responses to lightflecks ofFagus crenata seedlings grown in a gap and understory of a deciduous forest

Photosynthetic responses to a series of 1-min lightflecks (1,000μmol m⁻² s⁻¹) superimposed on a background with different duration (1, 5, and 10 min) and intensity (25 and 50μmol m⁻² s⁻¹) of low background photosynthetic photon flux density (PPFD) were measured in the leaves ofFagus crenata grown in a gap and understory of aFagus crenata forest in the Naeba Mountains. The two background PPFD intensities most frequently occurred in understory and gap sites respectively. The maximum net photosynthetic rate (P _Nmax) and maximum stomatal conductance (g _smax) were higher in the gap seedlings than in the understory seedlings. However, when the background PPFD was 25μmol m⁻²s⁻¹, the net photosynthetic rate (P ₂₅) and stomatal conductance (g _s25) were almost the same between the gap and understory. When the background PPFD duration was 1-min, the net photosynthetic rate (P _N ) at the end of each lightfleck increased progressively. When the background PPFD duration was 5- and 10-min, the increase inP _N at the end of each lightfleck was less. This indicates that background PPFD duration is important to photosynthetic responses to lightflecks. The higher ratios ofP ₂₅/P _Nmax andg _s25/g _smax in the understory seedlings indicate that the understory seedlings can maintain relatively lower levels of biochemical and stomatal limitations than the gap seedlings under low light conditions. The ratios ofP _N /P _Nmax at the end of each lightfleck (IS) and light utilization efficiency of single lightflecks (LUE _s) that showed the influence of lightflecks on carbon gain were higher in the understory seedlings than in the gap seedlings when the background PPFD was 25μmol m⁻² s⁻¹. This means that understory seedling are capable of utilizing fluctuating light more efficiently under low light conditions than the gap seedlings although the net carbon gain of single lightflecks (CG _s) in the understory seedlings was not higher than that in the gap seedlings. There were no significant differences inIS andLUE _s between understory seedlings at a background PPFD of 25μmol m⁻² s⁻¹ and gap seedlings at a background PPFD of 50μmol m⁻² s⁻¹. However,CG _s in gap seedlings was higher than in understory seedlings. These results provide more evidence thatF. crenata acclimate to a natural light environment in respect to relative induction state at low background PPFD and can capture the fluctuating light at the same efficiency in both the gap and understory seedlings under natural light environments. This study was funded by the research project, Evaluation of Total CO₂ Budget in Forest Ecosystems, coordinated by the Ministry of Agriculture, Forestry and Fisheries of Japan.     

枝梢环剥对油橄榄莱星品种果实产量及叶片光合作用的影响

[目的]研究冬季半休眠期枝梢环剥对油橄榄成花、坐果及叶片碳氮营养、光合作用的影响,探讨环剥技术对油橄榄大小年结果的调控作用及环剥后较长时期内叶片光合作用调控机制.[方法]以16年生油橄榄'莱星'典型的大、小年树为试验材料,研究了冬季半休眠期枝梢环剥对油橄榄成花、坐果及叶片碳氮营养、光合作用的影响.[结果]冬季半休眠期枝梢环剥可显著提高油橄榄大、小年树次年花芽形成率和早期坐果率(花后30天),但对最终的坐果率、单个果实干鲜质量和果实产量无明显影响.环剥后30天,叶片可溶性糖含量显著升高,叶片淀粉含量明显升高,叶片全氮含量显著下降,叶片碳氮比值显著升高;叶片净光合速率(P_n)和气孔导度(G_s)显著下降,叶片胞间CO₂浓度(C_i)基本未变.之后,随处理时间延长,叶片中可溶性糖和淀粉含量积累效应基本消失时(处理后120 d),叶片P_n和G_s仍显著低于对照,叶片C_i显著高于对照.[结论]冬季半休眠期枝梢环剥可促进油橄榄成花,但果实产量无显著提高;莱星品种明显的结实大小年节律可能主要决定于其品种的发育节律和遗传本身.环剥后短期内叶片P_n的下降应与叶片中可溶性糖和淀粉积累有关.     

角蜡蚧产卵量与卵期预测预报的研究

角蜡蚧是雪松等园林树木的重要害虫之一,产卵多、繁殖强、危害重,准确测报其发生量与若虫孵化期,是防治成败的关键。通过1997年5月对产卵末期雌虫体质量、体长及产卵量的测定与室内变温、恒温饲养研究,其平均虫体质量x₁=0.1103±0.0849g,体长x₂=7.027±0.202mm,产卵量(y₁)=4880.5±4440.53粒;产卵量与虫体质量、体长相关方程式分别为:y₁=-571.25+50078.3_x1,r₁=0.9719>r_0.01=0.496;y₂=-10356.46+1983.39_x2,r₂=0.8436>r_0.01=0.496.卵发育起点温度:C=10.25±1.53℃或C=9.94±0.19℃;有效积温K=165.15±6.96DD或K=141.51±2.15DD.经应用及检验与实际符合。     

应用单拷贝核基因标记研究我国欧洲山杨自然居群的遗传多样性

[目的]对分布于我国新疆地区欧洲山杨自然居群的遗传多样性与遗传分化进行研究。[方法]对4个欧洲山杨自然居群共72个个体的6个单拷贝核基因标记(sing-copy nuclear markers)进行扩增与测序,并计算相应的遗传多样性和遗传分化参数。[结果]表明:比对后6个基因的长度在459 bp到747 bp之间,平均多态核苷酸位点个数为14,遗传多样性指数π和θ_w分别达到了0.004 8和0.004 4,基因多样性指数为0.73,以上结果表明欧洲山杨表现出较高的遗传多样性水平。Tajima中性检验结果均不显著,表明所用6个单拷贝核基因均符合中性进化假设。AMOVA分析表明89.72%的遗传变异存在于居群内,居群间的平均遗传分化指数F_st为0.10,居群间平均基因流(Nm)为3.235。[结论]高度异交,高碱基突变率及超长距离的基因流机制能够很好的解释我国新疆地区欧洲山杨表现出的较高的遗传多样性水平与较低水平的遗传分化。     

I－69杨胶合板用材林密度及立地效应研究

以胶合板材为培育目标,研究了I-69杨胶合板用材林平均单株材积与造林密度和优势高的关系。分别不同林龄(6～11a)建立了平均单株材积与造林密度及优势高的模型V=a₀N^a₁ H₀^a₂,通过生产弹性分析、边际产量分析,研究了密度效应及优势高效应,计算出了不同林龄林分的生产弹性值和边际产量,并且根据立地及密度效应模型研究了造林密度、林龄、立地指数对林分蓄积的影响。认为在长江中、下游地区营造I-69杨胶合板用材林密度应适当减小,选择造林地时以立地指数大于等于20m林地为佳。     

长白山典型森林土壤黑碳含量及不同组分中的分布特征

[目的]通过实地采样对黑碳进行量化研究。[方法]利用相对密度分组方法探讨了长白山典型森林土壤黑碳含量及在不同有机碳组分中的分布特征。[结果]表明:黑碳(BC)含量在表层(A₁₁)、亚表层(A₁₂)分别为6.39~16.55 g·kg^-1、1.44~6.16 g·kg^-1,随土壤深度的增加而显著下降(p﹤0.01)。在A₁₁、A₁₂层中,轻组有机碳(LFOC)平均含量分别为66.66 g·kg^-1、6.65 g·kg^-1,轻组黑碳(LFBC)平均含量分别为5.63 g·kg^-1、1.21 g·kg^-1,同时,LFBC/LFOC在A₁₂层(10.02%~34.89%)显著高于A₁₁层(6.99%~14.45%)(p﹤0.01);A₁₁、A₁₂层重组有机碳(HFOC)平均含量分别为49.16 g·kg^-1、36.55 g·kg^-1,重组黑碳(HFBC)平均含量分别为2.69 g·kg^-1、1.44 g·kg^-1,HFBC/HFOC在A₁₁层(3.36%~8.08%)和A₁₂层(3.21%~7.58%)之间没有显著差异(p>0.05)。另外,土壤中LFBC/LFOC显著高于HFBC/HFOC(p﹤0.01),LFBC/BC显著高于HFBC/BC(p﹤0.01)。[结论]长白山典型森林土壤中黑碳的含量、比例均较高;土壤表层(A₁₁)有机碳、黑碳含量及各组分有机碳、黑碳含量均高于亚表层(A₁₂),均随着土层加深而显著降低;轻组、重组有机碳中均含有一定比例的黑碳,黑碳主要分布在轻组分中;轻组、重组有机碳与组分中黑碳均显著相关,轻组中相关系数大于重组。     

松材线虫(Bursaphelenchus xylophilus)耐久型幼虫(LIV)携带的香茅醇假单胞杆菌(Pseudomonas citronellolis)分离与鉴定

[目的]目前有关松材线虫与伴生细菌的关系及伴生细菌的病原作用是松树枯萎病研究的重点。为了揭示松材线虫与伴生细菌之间存在的密切关系,作者对松材线虫L_IV幼虫携带的细菌进行了分离鉴定。[方法]根据培养性状和16S rDNA序列同源性以及系统发育学等方面进行分析鉴定。[结果]确定L_IV幼虫携带的是香茅醇假单胞杆菌（Pseudomonas citronellolis）,携带率为100%;每条L_IV幼虫携带量在1.4×10⁵~4.5×10⁵。L_IV幼虫生活在松褐天牛体内,是引起松材线虫病侵染流行的唯一虫态;新发现的香茅醇假单胞杆菌能分解纤维素及降解或合成萜烯和酚类化合物。[结论]L_IV幼虫携带香茅醇假单胞杆菌的发现,揭示了松树、松褐天牛、松材线虫、细菌同为一体的紧密关系,并为揭示松树枯萎病机制提供了一种新病原和重要的研究思路。     

赣县稀土采矿区巨桉林地土壤抗蚀性评价

通过野外调查与室内分析相结合,应用主成分分析法,从衡量土壤抗蚀性的16个指标中,优化得到赣县稀土采矿区巨桉林地土壤抗蚀性7个最佳评价指标：分散系数（X₁）、团聚度（X₂）、>0.25 mm水稳性团聚体含量（X₃）、>0.5 mm水稳性团聚体含量（X₄）、<0.05 mm粉黏粒含量（X₅）、>0.25 mm团聚体破坏率（X₆）和<0.001 mm黏粒含量（X₇）,并以此为变量分析比较不同林龄巨桉林地土壤抗蚀性变化规律。结果表明：不同林龄巨桉林地土壤抗蚀性综合指数大小为：1年生林地>2年生林地>4年生萌芽1 a林地>裸露地。在此基础上,以上述7个评价指标为自变量,以土壤抗蚀性综合指数（Y）为因变量,进行回归分析,得出稀土采矿区土壤抗蚀性综合评价方程为：Y=0.309 X₁+0.038 X₂ -0.161 X₃ -0.643 X₄ +0.491 X₅ -0.032 8 X₆ +0.129 X₇ +41.637,因子决定系数R²=0.991 5,F=49.84,各因子间显著相关,方程拟合较好,可为构建稀土采矿区土壤抗蚀性评价指标体系提供依据。     

米槠人促更新林皆伐火烧后初期土壤CO2通量动态

[目的]为科学评价皆伐、火烧对中亚热带常绿阔叶林不同深度土壤有机碳吸存的影响,[方法]以福建省中亚热带36年生米槠人促更新林为研究对象,采用非散射红外CO₂浓度探测仪和Licor-8100土壤碳通量系统,并结合Fick扩散法计算并分析0~80 cm不同深度土层CO₂通量的日动态特征。[结果]表明:(1)火烧地(RB)和皆伐地(RR)不同土层CO₂浓度均出现明显下降,其中,对照(CK)地土壤CO₂浓度值(0~80 cm)分别是RB和RR的1.9、1.3倍;(2)各试验地土壤CO₂通量(0~80 cm)表现为RB(1.99 μmol·m²·s^-1)>RR(0.99 μmol·m²·s^-1)>CK(0.96 μmol·m²·s^-1),除2040 cm土层外,RB土壤各层CO₂通量均显著高于RR和CK(P<0.05);(3)试验地不同土层CO₂通量(0~80 cm)日变化幅度表现为RB>RR>CK,其中,RB土壤各层的变化幅度均显著大于RR和CK(P<0.05),而RR与CK间的差异表现在0~5、10~20、20~40 cm土层(P<0.05);(4)拟合分析表明,各试验地不同深度土壤CO₂通量与土壤温度呈显著相关,且 RB的决定系数(R²)显著高于RR和CK;不同试验地各土层温度、含水量的双因素模型拟合效果均优于单因素模型;Q₁₀值显示,皆伐、火烧后初期土壤各层的温度敏感性得到明显提高。     

大兴安岭森林沼泽类型与火干扰对土壤微生物群落影响

[目的]研究森林沼泽演替与火干扰条件下土壤微生物结构与多样性变化,为进一步揭示土壤微生物群落在森林沼泽保护与恢复中的作用提供依据。[方法]采用磷脂脂肪酸法与BIOLOG方法,研究大兴安岭南瓮河国家自然保护区内主要森林沼泽类型(兴安落叶松-狭叶杜香-藓类沼泽、兴安落叶松-兴安杜鹃-藓类沼泽、兴安落叶松+白桦-苔草沼泽)与2006年受不同火强度干扰沼泽(重度火烧的兴安落叶松-兴安杜鹃-藓类沼泽和中度火烧的兴安落叶松+白桦-苔草沼泽)土壤微生物群落特征,探讨沼泽主要发育阶段与火干扰强度对土壤微生物群落的影响。[结果]研究区域土壤微生物群落以16:00(16.29±5.62 nmol·g^-1)、甲烷氧化菌(18:1ω8t)(9.89±8.61 nmol·g^-1)与16:1ω7c(9.79±3.24 nmol·g^-1)的微生物为优势种群。土壤微生物总PLFAs含量、革兰氏阳性菌(G⁺)中a15:0、i16:0、i17:0、革兰氏阴性菌(G^-)中的cy19:0、真菌中的18:2ω6c、甲烷氧化菌(18:1ω8t)与森林沼泽发育阶段、火干扰明显相关(p<0.05)。一般饱和直链脂肪酸/单烯饱和脂肪酸比(Sat/Mon)偏低,其比值随沼泽发育呈现增加趋势,受到火干扰后明显增加(p<0.05);真菌/细菌比(F/B)与革兰氏阳性菌/革兰氏阴性菌(G⁺/G^-)未随着沼泽发育呈现出规律性变化,其比值受火干扰后明显发生改变(p<0.05)。土壤细菌与真菌对6类碳源的利用能力明显不同(p<0.001),其中土壤细菌对α-D-Lactose与L-Threonine利用存在差异性(F_α-D-Lactose =2.87 p=0.080,F_L-Threonine=3.00 p=0.078),土壤真菌对D-Mannitol、D-glucosaminic Acid利用存在差异性(F_{Tween 80}=2.75,p=0.088, F_D-Mannitol=3.53 p=0.047, F_{D-glucosaminic Acid}=4.67 p=0.022),但沼泽类型与火干扰未对土壤微生物功能多样性产生影响(p>0.05)。[结论]土壤微生物量与沼泽发育阶段相关;沼泽发育与火干扰改变土壤微生物群落结构。土壤细菌与真菌对碳源利用方面具有选择性。     

广东西樵山国家森林公园景观格局分析及优化

城郊森林公园是提升大众福祉、发挥生态功能的载体。以广东西樵山国家森林公园为研究对象，运用 ArcGIS 软件和Fragstats软件对其景观格局进行分析。结果表明，风景林是公园景观的基质（PLAND =67.84%），道路廊道将其与用材林、建筑和水体3种主要景观类型进行串联；公园各景观类型的破碎化程度不同，斑块形状均较为规则（MSI值为1.41~2.12；MPFD值为1.10~1.24）；公园的景观多样性较低（SHDI=1.31），斑块空间分布不均（SHEI=0.53），斑块形状较为复杂（LSI=22.83），各功能分区的格局特征差异明显。城郊森林公园的经营应严格控制人为干扰影响，提高公园景观多样性，注重斑块类型、功能分区和整体景观格局的优化。     

Large electro-fused protoplasts ofPopulus alba selected by a micromanipulator: Techniques and some characteristics of cells and their regenerants

An improved method for selection of large electro-fused protoplasts ofPopulus alba by a micromanipulator was developed. The conditions for electric cell fusion treatment were optimized. For the best result, protoplasts with a cell density of 5 × 10⁵/mL were treated with an alternate current (1 MHz, 200 V/cm) and pulsed with a direct current (2 kV/cm) for 100μs in 2.5 mM CaCl₂ and 0.55 M mannitol. The electo-fused protoplasts were cultured in NH₄NO₃-free Murashige and Skoog’s medium containing 0.6 M of mannitol, 0.09 M sucrose, 1μM of 2,4-dichlorophenoxyacetic acid and 0.1μM of benzyladenine, the same medium used for protoplast culture, but at a very low cell density of 5–10 × 10²/mL in a well of a 96-well culture plate. When cell aggregates derived from individual fused protoplasts were transferred to fresh medium with 0, 0.3 or 0.6 M mannitol, large colonies developed. In the shoot differentiation medium, the reaction of the calluses derived from large fused protoplasts towards the growth regulators differed from the non-fused ones. In medium containing 1μM each of naphthalene acetic acid andN-(2-chloro-4-pyridyl)-N′-phenylurea, growth of callus from electro-fused ones was not reduced by much compared to the control, but shoot differentiation was inhibited. Gibberellic acid (0.1–10μM) was beneficial to shoot regeneration; however, irregularly shaped leaves appeared at high gibberellic acid concentrations. Shoots regenerated were rooted in Murashige and Skoog’s medium containing 4μM of indole-3-butyric acid. Some plantlets obtained had a varied morphology. Based on the characteristics of growth, some cells derived from electro-fused protoplasts appear to be physiologically different from the non-fused one.     

Twelve elastic constants of Betula platyphylla Suk

Wood elastic constants are needed to describe the elastic behaviors of wood and be taken as an important design parameter for wood-based composite materials and structural materials. This paper clarified the relationships between compliance coefficients and engineering elastic constants combined with orthotropic properties of wood, and twelve elastic constants of Betula platyphylla Suk. were measured by electrical strain gauges. Spreading the adhesive quantity cannot be excessive or too little when the strain flakes were glued. If excessive, the glue layer was too thick which would influence the strain flakes’ performance, and if too little, glues plastered were not firm, which could not accurately transmit the strain. Wood as an orthotropic material, its modulus of elasticity and poisson’s ratios are related by two formulas: μ ij/Ei=μji/Ej and μ ij<(Ei/Ej)1/2. The results showed that the elastic constants of Betula platyphylla Suk. measured by electrical strain gauges were accurate and reliable. The results of shear elastic modulus G _TL and G _LR show a high linear regression correlation coefficient (>0.95) between the reciprocal of elastic modulus MOE ⁻¹ and the square of the ratio of depth to length (h/l)², which indicate that shear modulus values measured were reliable by three point bending experiment.     

胁迫条件下毛竹miR164b及其靶基因PeNAC1表达研究

MicroRNAs(miRNAs)在植物生长发育以及抗逆等过程中起着重要的调控作用。miR164 作为植物特有的miRNA,其主要的靶基因是植物NAC转录因子。为揭示毛竹 miR164 对其靶基因的调控机制,通过茎环引物法和RT-PCR技术,从毛竹(Phyllostachys edulis)中克隆出miR164b成熟序列及其靶基因PeNAC1。序列分析表明miR164b的靶点位于PeNAC1 编码区,RLM-5'RACE PCR产物测序结果证实切割位点位于靶点的第10-11位碱基之间。组织特异性表达分析表明,毛竹 miR164b和PeNAC1在根、茎、叶及鞘中均表达,其中miR164b在根中表达丰度最高,在茎中表达丰度最低;而PeNAC1的表达丰度恰好与miR164b 相反。实时定量PCR结果显示,NaCl(250 mmol·L^-1)、低温(4℃)和强光(1 500 μmol·m^-2·s^-1)处理后毛竹叶片中 miR164b 的表达均明显下调,GA₃(100 μmol·L^-1)处理后 miR164b表达量明显上调;而在同样处理条件下,PeNAC1的表达恰好呈现出与其完全相反的趋势。由此表明,miR164b对靶基因PeNAC1 具有表达调控作用,可能与毛竹响应非生物胁迫的抗逆过程密切相关,这为利用miRNA开展竹子抗逆分子育种提供了参考。     

Characterization and role of glucose-6-phosphate dehydrogenase of Populus suaveolens in induction of freezing resistance

Glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) was purified from the leaves of 8-week-old Populus suaveolens cuttings. The enzyme activity in the absence and presence of reduced dithiothreitol (DTT_red) was determined. The results show that the G6PDH activity is not inactivated by pre-incubation with DTT_red, indicating that the purified enzyme probably presented in cytosol of P. suaveolens. The catalytic characteristics and kinetic parameters of cytosolic G6PDH purified from P. suaveolens cuttings were also studied. The results show that G6PDH is characterized by K _m value of 360 μmol·L⁻¹ for G6P and 16 μmol·L⁻¹ for NADP, a pH range of 7.3-8.9, and the maximum activity around pH 8.2. The enzyme activity is inhibited by various metabolites such as NADPH, NADH, GTP, UTP, ATP, AMP, ADP, CoA, acetyl CoA, fructose-6-phosphate (F6P), erythrose-4-phosphate (E4P), ribose-5-phosphate (R5P) and 3-phosphoglycerate (3-PG) (all at 1 mmol·L⁻¹ except for NADPH and NADH) to different extents. NADPH is the most effective inhibitor of enzyme activity, with an inhibition of 72.0%. The addition of metal ions such as MgCl₂, CaCl₂ and KCl (all 1.0 mmol·L⁻¹) to the standard reaction mixture has no remarkable influence on the cytosolic G6PDH activity. However, CdCl₂ (1.0 mmol·L⁻¹) causes high inhibitory effect on the enzyme activity. To explore the role of G6PDH on the enhancement of freezing resistance induced by freezing acclimation, the changes in the cytosolic G6PDH activity and freezing resistance (expressed as LT₅₀) of P. suaveolens cuttings during freezing acclimation at −20 °C were investigated. The results reveal that freezing acclimation decreases LT₅₀ of cuttings, and increases the activity of cytosolic G6PDH compared with control ones, while 2 d of de-acclimation at 25 °C result in a decrease in cytosolic G6PDH activity, and caused an increase in LT₅₀. Furthermore, the change in cytosolic G6PDH activity is found to be closely correlated to the degree of freezing resistance of cuttings during freezing acclimation. It is suggested that cytosolic G6PDH may be involved in the induction of freezing resistance of cuttings. [Supported by the Foundation of State-designated Base for Biology Researching and Teaching in Beijing Forestry University]     

松材线虫Bxpel2基因的克隆及RNA干扰载体构建

[目的]为了构建松材线虫(Bursaphelenchus xylophilus)果胶酶Bxpel2基因干扰载体.[方法]通过Trizol 法提取松材线虫总RNA,反转录合成cDNA,设计带T₇启动子的果胶酶Bxpel2基因引物,以cDNA为模板扩增出果胶酶Bxpel2基因片段,连接到RNA干扰载体,再以干扰载体为模板,PCR扩增出目的片段后进行测序鉴定,合成果胶酶Bxpel2基因双链RNA(dsRNA),采用RT-PCR检测松材线虫Bxpel2基因干扰后的表达情况.[结果]表明:1)提取的松材线虫总RNA完整性好,无降解;2)成功克隆出松材线虫果胶酶Bxpel2基因片段(790 bp)并将其连接至pMD19-T载体;3)以RNA干扰载体为模板合成dsRNA,浓度分别为1.313 mg·mL^-1和1.152 mg·mL^-1;4)RT-PCR结果显示,松材线虫经过dsRNA干扰后,Bxpel2基因表达基本受到抑制.[结论]成功构建松材线虫果胶酶Bxpel2基因干扰载体,为进一步研究Bxpel2基因在松材线虫致病过程中的作用和功能奠定了良好的基础.     

余甘子精粉的体外抗氧化活性分析

The antioxidant activities in vitro of refined powder of Phyllanthus emblica L. were detected by methods based on chemical measurement and cell modeling. The results of anti-peroxidation ability and iron reduction ability trials showed that the refined powder of P. emblica L. had strong ability of anti-peroxidation, and it increased with the increasing of concentration with a clear dose-response relationship. When the concentration reached 800 μg·mL^-1, the ability of anti-peroxidation was almost equal to the positive control VC with the same concentration. Meanwhile, it also had iron reduction ability that accompanied by significant dose-response relationship. By in vitro cell culture method, H₂O₂ was used to induce SH-SY5Y cells damages to establish the cell model of oxidative damage. The author detected the effect of different concentrations of powder on cell survival rate for the model cells by MTT assay. The results indicated that refined powder could show better protective effect to oxidative damaged SH-SY5Y cells in the range of 600 1 200 μg·mL^-1. When the concentration reached 1 200 μg·mL^-1, the cell survival rate was the highest and refined powder exhibited the best antioxidant activity. Both methods proved the strong antioxidant activities of refined powder of P. emblica L. in vitro.